In my analysis of global clean energy research, I focus on one of the most dynamic and disruptive directions in modern photovoltaics: the tandem perovskite solar cell. The transition from fossil-fuel-based energy systems to renewable energy systems is no longer a distant policy aspiration; it is an urgent scientific, engineering, and economic necessity. Among renewable technologies, solar photovoltaics has become the most scalable and cost-effective pathway for decarbonizing electricity generation. Within this broad landscape, the perovskite solar cell has emerged as a revolutionary platform because of its rapidly increasing power conversion efficiency, low-temperature processability, and compatibility with diverse substrates. However, single-junction perovskite solar cell devices are constrained by the Shockley–Queisser detailed-balance limit, which places a theoretical ceiling on their efficiency. To move beyond this ceiling, researchers have turned to tandem architectures, especially perovskite–silicon tandems and all-perovskite tandems. In this article, I use bibliometric and science-mapping methods to examine the global frontier trends of clean energy development through the lens of tandem perovskite solar cell research from 2015 to 2025. My aim is not merely to count publications but to reveal the knowledge structure, collaboration patterns, thematic evolution, and emerging technological pathways that define this field. By combining CiteSpace, VOSviewer, and online bibliometric platforms, I quantify the dynamics of a research area that sits at the intersection of materials science, device physics, interface engineering, and industrial policy.
The central object of my inquiry, the tandem perovskite solar cell, represents a convergence of two major photovoltaic strategies. The first strategy is spectral splitting: stacking absorber layers with different bandgaps so that high-energy photons are absorbed by a wide-bandgap top cell and low-energy photons are transmitted to a narrower-bandgap bottom cell. The second strategy is loss reduction: by reducing thermalization losses and transmission losses, a tandem device can convert a larger fraction of the solar spectrum into useful electrical power. In a two-terminal tandem perovskite solar cell, the top and bottom subcells are monolithically integrated and connected by a tunnel junction or recombination layer. In a four-terminal tandem perovskite solar cell, the subcells are mechanically stacked and independently contacted. Both configurations have attracted intense research interest, but the two-terminal architecture has become especially prominent because of its potential for lower manufacturing cost and higher module-level integration. My bibliometric analysis shows that the phrase “perovskite solar cell” appears across multiple thematic clusters, including high efficiency, defect passivation, interface engineering, wide-bandgap perovskites, self-assembled monolayers, phase segregation, and device stability. This lexical diversity reflects the multidimensional nature of the field: a tandem perovskite solar cell is not simply a material or a device; it is a complex system in which optical, electrical, chemical, and mechanical properties must be co-optimized.
To ground my analysis in quantitative terms, I first define the core performance metrics of a perovskite solar cell and its tandem derivatives. The power conversion efficiency of any solar cell can be written as:
$$ \eta = \frac{P_{max}}{P_{in}} = \frac{J_{sc} V_{oc} FF}{P_{in}} $$
Here, \(J_{sc}\) is the short-circuit current density, \(V_{oc}\) is the open-circuit voltage, \(FF\) is the fill factor, and \(P_{in}\) is the incident solar power density, typically taken as \(1000\ \mathrm{W/m^2}\) under standard AM1.5G illumination. For a single-junction perovskite solar cell, the detailed-balance or Shockley–Queisser limit can be expressed conceptually as:
$$ \eta_{SQ} = \frac{J_{sc}^{SQ} V_{oc}^{SQ} FF^{SQ}}{P_{in}} $$
For a tandem perovskite solar cell, the efficiency is not simply the sum of the two subcell efficiencies, because optical and electrical coupling introduce additional gains and losses:
$$ \eta_{tandem} = \eta_{top} + \eta_{bottom} – \Delta \eta_{optical} – \Delta \eta_{electrical} – \Delta \eta_{recombination} $$
The bandgap combination is critical. For a two-terminal perovskite–silicon tandem, the top perovskite solar cell usually has a bandgap between approximately \(1.65\ \mathrm{eV}\) and \(1.75\ \mathrm{eV}\), while the bottom silicon cell has a bandgap near \(1.1\ \mathrm{eV}\). For an all-perovskite tandem, the top wide-bandgap perovskite solar cell is often tuned to \(1.70\ \mathrm{eV}\) to \(1.85\ \mathrm{eV}\), and the bottom narrow-bandgap perovskite solar cell is based on tin–lead compositions with a bandgap near \(1.0\ \mathrm{eV}\) to \(1.2\ \mathrm{eV}\). The optimal bandgap matching condition can be approximated as:
$$ E_{g,top} + E_{g,bottom} \approx 2.8\ \mathrm{eV} $$
These equations help explain why the tandem perovskite solar cell has become a focal point of clean energy research. The theoretical efficiency of a tandem device can exceed \(40\%\), far beyond the single-junction limit, but realizing this potential requires precise control of crystallization, interfaces, defects, phase stability, and large-area uniformity. My bibliometric results show that these challenges have shaped the field’s publication trajectory, collaboration networks, and keyword evolution.
For data collection, I used the Web of Science Core Collection as the primary source. The search period extended from January 1, 2015, to November 11, 2025. I restricted the document type to articles and applied a query designed to capture perovskite tandem photovoltaics broadly. The query combined terms related to perovskite, perovskite solar cell, perovskite tandem, perovskite–silicon, perovskite/silicon, and stacked or multi-junction solar cells. After removing noise, reviews, conference papers, and retracted items, I obtained a final corpus of 2,550 articles. I then used CiteSpace and VOSviewer to analyze temporal trends, spatial distribution, institutional collaboration, author co-authorship, keyword co-occurrence, cluster timelines, and burst terms. I also cleaned and merged synonymous keywords to reduce the subjective influence of terminological variation. Table 1 summarizes the main methodological parameters.
| Parameter | Description |
|---|---|
| Database | Web of Science Core Collection |
| Time span | January 1, 2015 – November 11, 2025 |
| Document type | Articles only; reviews, conference papers, and retracted publications excluded |
| Search logic | Perovskite-related terms combined with tandem, multi-junction, stacked solar, perovskite–silicon, and related expressions |
| Final corpus | 2,550 articles after noise removal |
| Analytical tools | CiteSpace, VOSviewer, online bibliometric analysis platform |
| Analytical dimensions | Temporal evolution, spatial distribution, collaboration networks, keyword co-occurrence, clustering, burst detection |
| Keyword processing | Cleaning and merging of synonymous terms; exclusion of generic terms such as perovskite, solar cells, and tandem solar cells for deeper hotspot detection |
The temporal trend of publication output reveals three distinct phases in the development of tandem perovskite solar cell research. From 2015 to 2018, the field was in an embryonic stage. Annual publication volume remained below 150 articles. In 2015, only 36 articles were published. Early work demonstrated the feasibility of a two-terminal perovskite/silicon multijunction solar cell enabled by a silicon tunnel junction, laying the foundation for subsequent research. From 2019 to 2021, the field entered a period of technical攻坚, or intensive technical exploration. Annual output rose from approximately 150 to 221 articles, with a slight decline in 2019 and a slowdown in 2021. From 2022 onward, the field entered a rapid growth phase. Publication volume reached 295 articles in 2022, 365 in 2023, and 441 in 2024. By November 11, 2025, the number had already reached 531, indicating sustained and accelerating research activity. This trajectory suggests that tandem perovskite solar cell research has moved from proof-of-concept to规模化, or large-scale, investigation. Table 2 summarizes the phased publication trend and its main characteristics.
| Phase | Period | Annual output range | Main characteristics |
|---|---|---|---|
| Embryonic phase | 2015–2018 | 36–150 articles | Early demonstration of two-terminal perovskite/silicon tandems; proof of concept; optical and material foundations |
| Technical攻坚 phase | 2019–2021 | 141–221 articles | Interface engineering, tunnel junctions, wide-bandgap perovskites, stability challenges |
| Rapid growth phase | 2022–2025 | 295–531 articles | Efficiency optimization, all-perovskite tandems, self-assembled monolayers, commercialization-oriented research |
The phased growth of publication output is closely linked to policy drivers. Around 2021, several major economies introduced or strengthened national plans that explicitly identified perovskite solar cell technology as a strategic priority. China’s energy science and technology innovation plans listed perovskite solar cells as a key development direction, and subsequent renewable energy and smart photovoltaic pilot programs further supported the field. In the United States, the Inflation Reduction Act of 2022 provided tax incentives for domestic manufacturing of thin-film photovoltaic components and solar materials, including perovskite-based technologies. The European Union supported projects aimed at scaling perovskite–silicon tandem devices from laboratory dimensions to industrial dimensions. Japan’s climate policy framework emphasized next-generation solar cells, including perovskite solar cell technology, to meet future electricity price targets. South Korea published industrial roadmaps supporting high-efficiency photovoltaic products. These policy interventions collectively created a favorable environment for the rapid growth of tandem perovskite solar cell research. My analysis therefore suggests that the field is not driven by scientific curiosity alone; it is co-produced by scientific advances, industrial expectations, and geopolitical competition in clean energy technology.
In terms of national distribution, China occupies the leading position. My bibliometric data show that China produced 1,202 articles, nearly half of the total corpus. Germany followed with 318 articles, the United States with 317, South Korea with 186, the United Kingdom with 159, India with 149, Australia with 137, Switzerland with 131, Japan with 127, and Saudi Arabia with 125. This distribution indicates a multipolar research landscape, but with a pronounced Chinese concentration. The strong Chinese presence aligns with national policy support, large-scale research funding, and a mature photovoltaic manufacturing ecosystem. Germany and the United States remain highly influential, particularly in fundamental device physics, interface engineering, and advanced characterization. European countries, including Switzerland, the United Kingdom, France, the Netherlands, and Germany, form a dense regional collaboration cluster. Saudi Arabia and Singapore act as bridge nodes, facilitating knowledge transfer between Asia, Europe, and the Middle East. Table 3 ranks the top ten countries by publication volume.
| Rank | Country | Articles | Share of total corpus |
|---|---|---|---|
| 1 | China | 1,202 | Approximately 47.1% |
| 2 | Germany | 318 | Approximately 12.5% |
| 3 | United States | 317 | Approximately 12.4% |
| 4 | South Korea | 186 | Approximately 7.3% |
| 5 | United Kingdom | 159 | Approximately 6.2% |
| 6 | India | 149 | Approximately 5.8% |
| 7 | Australia | 137 | Approximately 5.4% |
| 8 | Switzerland | 131 | Approximately 5.1% |
| 9 | Japan | 127 | Approximately 5.0% |
| 10 | Saudi Arabia | 125 | Approximately 4.9% |
At the institutional level, national research systems play a dominant role. My analysis shows that a leading Chinese national academy produced 308 articles, ranking first by a wide margin. Its affiliated university ranked fourth, reflecting the enormous institutional scale of Chinese research in tandem perovskite solar cell technology. A major German research federation ranked second with 154 articles, and its materials and energy center ranked seventh with 79 articles. A Swiss federal institute of technology ranked third with 121 articles. A U.S. national energy agency ranked fifth with 83 articles. Additional leading institutions include a major Chinese university in Tianjin with 83 articles, a major Chinese university in Wuhan with 78 articles, an international university in Saudi Arabia with 75 articles, and a major Chinese university in Suzhou with 74 articles. These patterns indicate that tandem perovskite solar cell research is concentrated in large national laboratories, elite universities, and cross-institutional research consortia. Table 4 presents the top ten institutions by publication volume in generalized form.
| Rank | Institution type | Articles | Country/region |
|---|---|---|---|
| 1 | Leading national research academy | 308 | China |
| 2 | National research federation | 154 | Germany |
| 3 | Federal institute of technology | 121 | Switzerland |
| 4 | Affiliated university of national academy | 104 | China |
| 5 | National energy agency | 83 | United States |
| 6 | Major research university | 83 | China |
| 7 | Materials and energy research center | 79 | Germany |
| 8 | Major research university | 78 | China |
| 9 | International science and technology university | 75 | Saudi Arabia |
| 10 | Major research university | 74 | China |
The national collaboration network exhibits a core–periphery structure. China, the United States, Germany, and South Korea occupy central hub positions. Saudi Arabia and Singapore function as active bridges, connecting otherwise separate regional clusters. Many European countries maintain dense intra-regional links, reflecting the role of European integration frameworks in promoting collaborative research on the perovskite solar cell and its tandem derivatives. In my view, this structure has important implications. First, the dominance of a few core countries means that the global research agenda is shaped by a relatively small number of funding systems and research cultures. Second, the bridge role of certain countries suggests that scientific diplomacy and international mobility can accelerate the diffusion of tandem perovskite solar cell knowledge. Third, the strong regional clustering in Europe indicates that policy coordination can create durable collaborative advantages, even when individual countries are smaller than China or the United States.
The institutional co-occurrence network displays two notable features. The first is the主导 role of national research systems. The most prolific institutions are national academies, national laboratories, and federally supported research organizations. This pattern suggests that tandem perovskite solar cell development depends on long-term strategic investment, shared infrastructure, and patient capital. The second feature is strategic complementarity in cross-border collaboration. For example, leading European universities collaborate with Middle Eastern and Chinese universities on wide-bandgap perovskite solar cells, interface passivation, and large-area tandem devices. These partnerships are not merely symbolic; they combine complementary expertise in materials synthesis, advanced characterization, device fabrication, and scale-up. In my bibliometric reading, the collaboration network is therefore both a map of scientific capacity and a map of strategic dependency.
Author co-authorship analysis provides a finer-grained view of research organization. I imported the corpus into VOSviewer, set the maximum number of authors per document to 25, and selected authors with at least 15 publications. From 11,004 authors, 127 core productive authors were identified as network nodes. The resulting network reveals several major research teams. One team focuses on perovskite/silicon tandem interface engineering and field-effect passivation, achieving certified efficiencies above 33% for fully textured tandem devices and above 28% for triple-junction perovskite/perovskite/silicon devices. Another team focuses on crystallization control in wide-bandgap perovskites for all-perovskite tandems, reporting small-area efficiencies above 28% and large-area module efficiencies above 28%. A third team works on two-terminal planar perovskite/silicon tandem solar cells, achieving power conversion efficiencies above 30% with open-circuit voltages near 1.95 V. A fourth team develops narrow-bandgap bottom cells and all-perovskite tandems with efficiencies above 28%. A fifth team emphasizes large-area all-perovskite tandem modules and commercialization, with certified efficiencies exceeding 29%. A sixth team has demonstrated certified perovskite–silicon tandem efficiencies above 32%. These teams are not isolated; they are connected through co-authorship, shared facilities, and complementary materials and device expertise. Table 5 summarizes the main collaboration network characteristics.
| Network level | Key observation | Implication for tandem perovskite solar cell research |
|---|---|---|
| Country level | China, Germany, United States, South Korea as core hubs; Saudi Arabia and Singapore as bridges | Multipolar knowledge production with strong regional clusters and strategic international linkages |
| Institution level | National academies and national laboratories dominate; cross-border partnerships combine complementary expertise | High dependence on long-term public investment and shared infrastructure |
| Author level | 127 core authors form multiple dense teams; team sizes are large and interdisciplinary | Research is organized around device efficiency, stability, interface engineering, and scale-up |
| Geographic pattern | European regional integration; Asian productivity concentration; Middle Eastern bridge institutions | Policy coordination and mobility shape the global research frontier |
Keyword co-occurrence analysis reveals the intellectual structure of the field. After excluding generic terms such as perovskite, perovskite solar cell, tandem solar cells, and solar cells, I found that the most frequent and central keywords include perovskite/silicon tandem solar cells, all-perovskite tandem solar cells, high efficiency, defect passivation, interface engineering, and wide-bandgap perovskite. These terms are not isolated; they are densely connected. The centrality of perovskite/silicon tandem solar cells and all-perovskite tandem solar cells indicates that the field has converged on two main technological routes. The frequency of high efficiency reflects the overarching goal of the field. The prominence of defect passivation and interface engineering shows that performance improvements depend heavily on controlling non-radiative recombination and chemical degradation at surfaces and grain boundaries. The emergence of wide-bandgap perovskite as a major node highlights the critical role of the top cell in tandem perovskite solar cell architectures. Table 6 summarizes the key keyword co-occurrence patterns.
| Keyword | Frequency/centrality pattern | Thematic role |
|---|---|---|
| Perovskite/silicon tandem solar cells | Very high frequency and strong centrality | Main commercializable tandem route leveraging silicon manufacturing |
| All-perovskite tandem solar cells | High frequency and strong centrality | Low-cost, lightweight, flexible tandem route |
| High efficiency | High frequency | Core performance target |
| Defect passivation | High frequency; strong links to efficiency and stability | Suppression of non-radiative recombination |
| Interface engineering | High frequency; strong links to tandem devices | Control of energy alignment, recombination, and degradation |
| Wide-bandgap perovskite | Emerging high-frequency node | Top-cell absorber for tandem perovskite solar cell |
| Self-assembled monolayers | Increasing burst strength | Hole-selective contacts and interface passivation |
| Phase segregation | Persistent burst term | Stability bottleneck in wide-bandgap perovskites |
Timeline clustering provides a historical view of how research themes have evolved. The keyword timeline network contains eight major clusters: perovskite solar cells, high efficiency, solar cells, light trapping, inorganic perovskite solar cells, tandem solar cells, device stability, and phase segregation. The structure is bipolar, with perovskite solar cells and tandem solar cells as dual cores. Subthemes such as light trapping, phase segregation, and high efficiency form specialized branches around these cores. In my interpretation, this clustering pattern shows that the field has matured from a broad exploration of perovskite solar cell materials into a more differentiated research system. Early work emphasized light management, transparent electrodes, electron transport layers, and optical simulation. Middle-period work focused on bandgap tuning, vacuum deposition, bifacial solar cells, and wide-bandgap absorbers. Recent work has shifted toward perovskite–silicon tandem solar cells, semi-transparent perovskite solar cells, interface modification, phase segregation, self-assembled monolayers, inverted perovskite solar cells, and defect passivation. This evolution reflects a transition from fundamental material discovery to device-level optimization and pre-commercialization.
Burst detection offers a particularly useful way to identify emerging frontiers. The burst terms from 2015 to 2020 include light trapping, transparent electrode, electron transport layer, optical simulation, and planar perovskite solar cells. These terms are associated with the optical and electronic foundations of tandem perovskite solar cell design. From 2020 to 2022, burst terms include band gap, vacuum deposition, bifacial solar cells, transparent electrode, photovoltaic cells, wide band gap, and black silicon. This period marks a shift from macroscopic optical design to microscopic carrier behavior and bandgap engineering. From 2022 to 2025, burst terms include organic tandem solar cells, perovskite–silicon tandem solar cells, semi-transparent perovskite solar cells, interface modification, phase segregation, self-assembled monolayers, inverted perovskite solar cells, and defect passivation. These terms indicate that the frontier has diversified into high-efficiency tandem structures and commercialization-oriented process technologies. Table 7 summarizes the burst terms and their periods.
| Period | Burst terms | Interpretation |
|---|---|---|
| 2015–2020 | Light trapping, transparent electrode, electron transport layer, optical simulation, planar perovskite solar cells | Foundational optical and electronic design for tandem perovskite solar cell efficiency |
| 2020–2022 | Band gap, vacuum deposition, bifacial solar cells, transparent electrode, photovoltaic cells, wide band gap, black silicon | Bandgap engineering, carrier behavior, and structural exploration |
| 2022–2025 | Organic tandem solar cells, perovskite–silicon tandem solar cells, semi-transparent perovskite solar cells, interface modification, phase segregation, self-assembled monolayers, inverted perovskite solar cells, defect passivation | Efficiency optimization, stability improvement, and commercialization-oriented process innovation |
Based on keyword co-occurrence, clustering, and burst detection, I identify three major research hotspots and frontiers: tandem structure type exploration, efficiency improvement pathways, and wide-bandgap perovskite material development. These three directions are interrelated. The choice of tandem structure determines the bandgap combination and the device architecture. The efficiency improvement pathway determines which interface, defect, and optical strategies are most urgent. The development of wide-bandgap perovskite materials determines whether the top cell can deliver high voltage, high current, and long-term stability. In the following sections, I analyze each direction in detail.
The first hotspot is tandem structure type exploration. My keyword analysis shows that perovskite–silicon tandem solar cells and all-perovskite tandem solar cells dominate the co-occurrence network. The node sizes for these two terms are significantly larger than those for earlier structures such as perovskite/organic tandems. This distribution reflects a broad consensus that these two routes have the greatest commercial potential. The perovskite–silicon tandem solar cell can leverage the mature silicon photovoltaic supply chain, including wafering, cell fabrication, module assembly, and reliability testing. This advantage reduces the barrier to market entry and allows rapid industrial learning. The all-perovskite tandem solar cell, by contrast, offers low-temperature solution processing, lightweight form factors, and flexibility. It is attractive for applications where weight, bendability, and low cost are critical, such as building-integrated photovoltaics, vehicle-integrated photovoltaics, portable power, and aerospace. However, the all-perovskite tandem faces a major challenge: thermal stability. The narrow-bandgap tin–lead perovskite solar cell is particularly susceptible to oxidation and degradation. My co-occurrence analysis shows that the term “thermal stability” is tightly linked to the all-perovskite tandem cluster. This link suggests that stability is not a secondary concern but a core technical bottleneck. Researchers have proposed several strategies to address it, including A-site cation engineering with large organic cations, X-site halide doping, suppression of halide phase segregation in wide-bandgap subcells, and the use of tunnel junctions with low interfacial diffusion. Table 8 compares the two main tandem routes.
| Feature | Perovskite–silicon tandem | All-perovskite tandem |
|---|---|---|
| Top cell | Wide-bandgap perovskite solar cell | Wide-bandgap perovskite solar cell |
| Bottom cell | Silicon solar cell | Narrow-bandgap tin–lead perovskite solar cell |
| Bandgap combination | Approximately 1.65–1.75 eV / 1.1 eV | Approximately 1.70–1.85 eV / 1.0–1.2 eV |
| Main advantage | Compatibility with mature silicon industry | Low cost, lightweight, flexible |
| Main challenge | Interface recombination, top-cell stability, scale-up | Tin oxidation, thermal stability, phase segregation |
| Commercial readiness | Relatively advanced | Earlier stage but rapidly progressing |
| Representative efficiency | Certified above 34% for small cells | Certified above 30% for small cells |
The second hotspot is efficiency improvement pathway攻关. Power conversion efficiency is the central target of tandem perovskite solar cell research. According to the latest efficiency tables, perovskite/silicon tandem solar cells have reached certified efficiencies above 34.85% for small-area devices, and large-area commercial-sized modules have reached approximately 33%. In all-perovskite tandems, small-area devices have exceeded 30.10%, and large-area devices above 1 cm² have reached approximately 28.20%. These values are remarkable when compared with the early laboratory efficiency of 3.8% for single-junction perovskite solar cells. The rapid improvement has been driven by several key technologies. Interface engineering and defect passivation are the most frequent调控 techniques in my keyword network. Interface engineering includes the insertion of hole-selective contacts, electron transport layers, recombination layers, and tunnel junctions. Defect passivation includes Lewis base passivation, ionic passivation, polymer passivation, and self-assembled monolayer treatment. These strategies reduce non-radiative recombination, improve charge extraction, and enhance device stability. The efficiency gain from passivation can be expressed conceptually as:
$$ \Delta \eta = \eta_{passivated} – \eta_{unpassivated} = \frac{\Delta J_{sc} V_{oc} FF + J_{sc} \Delta V_{oc} FF + J_{sc} V_{oc} \Delta FF}{P_{in}} $$
This equation shows that efficiency improvement is not a single-variable problem. A passivation strategy may increase \(V_{oc}\) by reducing trap-assisted recombination, increase \(J_{sc}\) by improving carrier collection, or increase \(FF\) by reducing series resistance and shunt pathways. In high-performance tandem perovskite solar cell devices, all three parameters must be optimized simultaneously. My analysis of the literature suggests that the most successful strategies combine bulk defect suppression with surface and interface passivation. For example, rigid passivation molecules can improve steady-state efficiency in perovskite/CIGS tandems. Benzene-derivative ligands with tuned binding strength and acidity can passivate the perovskite/C60 interface and enable hysteresis-free perovskite/silicon tandem solar cells with certified efficiencies above 31.7%. These findings indicate that molecular design is becoming an increasingly precise engineering discipline.
The third hotspot is wide-bandgap perovskite material development. Wide-bandgap perovskite is the top-cell absorber in most tandem perovskite solar cell architectures. Its bandgap typically ranges from 1.65 eV to 1.85 eV, depending on the tandem configuration. The material faces several challenges: phase segregation, ion migration, lattice strain, and defect-mediated degradation. My keyword cluster analysis shows that wide-bandgap perovskite forms an independent and highly connected network. The term “phase segregation” has a high burst strength, indicating that it is a persistent frontier issue. Researchers have found that defect-mediated degradation and quasi-Fermi level splitting shrinkage are key factors limiting wide-bandgap device performance. Additives such as thienothiophene derivatives can synergistically passivate bulk and interface defects, leading to efficiencies above 22% for wide-bandgap perovskite solar cells and above 28% for four-terminal all-perovskite tandems. Nicotinamide derivatives can regulate crystallization and improve photovoltaic preferred orientation, enabling all-perovskite tandem efficiencies above 28.5%. These results suggest that wide-bandgap perovskite research is moving from empirical optimization to rational design. Table 9 summarizes representative efficiency milestones and the associated technical strategies.
| Device type | Representative efficiency | Key strategy |
|---|---|---|
| Perovskite–silicon tandem solar cell | Above 34.85% certified small-area; approximately 33% large-area module | Interface engineering, field-effect passivation, textured silicon, tunnel junction optimization |
| Triple-junction perovskite/perovskite/silicon | Above 28.70% | Stabilized perovskite phases, current matching, recombination layer design |
| All-perovskite tandem solar cell | Above 30.10% small-area; above 28.20% large-area | Wide-bandgap crystallization control, narrow-bandgap tin–lead optimization, tunnel junction |
| Perovskite/CIGS tandem | Above 27.93% steady-state | Rigid passivation molecules, interface defect suppression |
| Perovskite/silicon tandem with self-assembled monolayer | Above 32.13% with certified 31.72% | Ligand binding strength and acidity tuning, hysteresis-free operation |
| Wide-bandgap perovskite solar cell | Above 22.40% | Additive-assisted bulk and interface passivation |
My analysis also reveals several cross-cutting challenges that will shape the future of tandem perovskite solar cell research. The first is the trade-off between high efficiency and long-term stability. Tandem devices must withstand heat, moisture, illumination, and electrical bias for decades. The wide-bandgap perovskite solar cell is particularly vulnerable to phase segregation and ion migration. The narrow-bandgap tin–lead perovskite solar cell is vulnerable to oxidation. The tunnel junction and recombination layer can suffer from diffusion and delamination. Therefore, stability is not a single material property; it is a system-level property. I summarize the main stability challenges and potential solutions in Table 10.
| Challenge | Mechanism | Potential solution |
|---|---|---|
| Phase segregation in wide-bandgap perovskite | Light-induced halide demixing and ion migration | Compositional engineering, additive passivation, strain management |
| Tin oxidation in narrow-bandgap perovskite | Sn2+ oxidation to Sn4+ under ambient conditions | Antioxidant additives, encapsulation, inert processing |
| Interface recombination | Defect states at perovskite/transport layer interfaces | Self-assembled monolayers, interface modifiers, buffer layers |
| Tunnel junction degradation | Diffusion, delamination, and resistance growth | Thin-film barrier layers, low-temperature processing, optimized doping |
| Large-area uniformity | Non-uniform crystallization and film thickness | Scalable deposition, ink engineering, process control |
| Lead toxicity | Leaching and environmental exposure | Lead-free perovskites, encapsulation, life-cycle assessment |
The second cross-cutting challenge is environmental sustainability. The mainstream perovskite solar cell still relies on lead-based compositions. Although the amount of lead per unit area may be small, the toxicity issue cannot be ignored. Future research should accelerate the development of lead-free perovskite materials, green solvents, recyclable substrates, and closed-loop manufacturing. In parallel, life-cycle assessment methods should be integrated into device research so that efficiency gains are not achieved at the expense of environmental harm. In my view, the clean energy credentials of tandem perovskite solar cell technology depend not only on its operational carbon footprint but also on its material sourcing, manufacturing energy, and end-of-life management.
The third cross-cutting challenge is the industrialization pathway. Commercialization requires more than high laboratory efficiency. It requires cost control, process compatibility, equipment standardization, yield improvement, and bankability. My bibliometric analysis shows that recent research has shifted toward inverted perovskite solar cells, self-assembled monolayers, semi-transparent perovskite solar cells, and large-area fabrication. These terms are closely associated with industrial translation. However, the innovation chain still suffers from disconnection between academia and industry. Laboratory breakthroughs often rely on spin coating, glovebox processing, and small-area devices, whereas industry requires scalable deposition, high-throughput manufacturing, and rigorous reliability testing. Therefore, I recommend building closer collaborative mechanisms among universities, research institutes, equipment manufacturers, material suppliers, and photovoltaic module companies. Table 11 summarizes my recommendations for future research and industrial policy.
| Direction | Recommended action | Expected outcome |
|---|---|---|
| Stability mechanism | Develop multi-scale characterization and predictive degradation models for tandem perovskite solar cell devices | Longer lifetime, better certification, improved bankability |
| Process innovation | Scale up deposition, patterning, and encapsulation for large-area tandem perovskite solar cell modules | Lower cost per watt, higher manufacturing yield |
| Materials design | Accelerate wide-bandgap and narrow-bandgap perovskite optimization; explore lead-free alternatives | Improved efficiency, reduced toxicity, broader application |
| Interface engineering | Design self-assembled monolayers, tunnel junctions, and recombination layers with high stability | Reduced recombination, higher voltage, improved fill factor |
| Industry–academia collaboration | Create shared pilot lines, standards, and reliability test protocols | Faster translation from laboratory to factory |
| International cooperation | Strengthen cross-border research and intellectual property coordination | Accelerated global deployment of clean energy technology |
In conclusion, my bibliometric analysis of tandem perovskite solar cell research from 2015 to 2025 reveals a field in rapid transition. Publication output has grown from 36 articles in 2015 to 531 articles by November 2025, with a clear three-phase pattern: embryonic exploration, technical攻坚, and rapid growth. China leads in publication volume, but Germany, the United States, South Korea, the United Kingdom, India, Australia, Switzerland, Japan, and Saudi Arabia form a multipolar collaboration network. National research academies, federal laboratories, and elite universities dominate institutional output, reflecting the high capital intensity and long-term strategic nature of tandem perovskite solar cell development. Keyword co-occurrence and burst detection show that the field has moved from light trapping and transparent electrodes to wide-bandgap perovskites, interface modification, self-assembled monolayers, phase segregation, and defect passivation. The two main technological routes are perovskite–silicon tandems and all-perovskite tandems. Efficiency has improved dramatically, with certified perovskite–silicon tandem efficiencies above 34% and all-perovskite tandem efficiencies above 30% for small-area devices. Yet major challenges remain, including thermal stability, phase segregation, tin oxidation, lead toxicity, large-area uniformity, and the disconnect between laboratory innovation and industrial production.
From my perspective, the future of the tandem perovskite solar cell depends on three systemic advances. The first is mechanistic understanding. Researchers must move beyond empirical passivation and develop predictive models that link composition, processing, defect chemistry, and device lifetime. The second is process innovation. Laboratory-scale excellence must be translated into scalable, reproducible, and standardized manufacturing. The third is collaborative governance. Clean energy technologies are global public goods, and their development benefits from international cooperation, open science, and coordinated standards. If these three advances are achieved, the tandem perovskite solar cell can become a cornerstone of the next generation of clean energy systems. My analysis suggests that the scientific frontier is already shifting from “can we make it efficient?” to “can we make it stable, scalable, affordable, and sustainable?” The answer to that question will determine whether the perovskite solar cell and its tandem derivatives fulfill their transformative promise.