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Enhancing electron diffusion length in narrow-bandgap perovskites for efficient monolithic perovskite tandem solar cells
摘要： Developing multijunction perovskite solar cells (PSCs) is an attractive route to boost PSC efficiencies to above the single-junction Shockley-Queisser limit. However, commonly used tin-based narrow-bandgap perovskites have shorter carrier diffusion lengths and lower absorption coefficient than lead-based perovskites, limiting the efficiency of perovskite-perovskite tandem solar cells. In this work, we discover that the charge collection efficiency in tin-based PSCs is limited by a short diffusion length of electrons. Adding 0.03 molar percent of cadmium ions into tin-perovskite precursors reduce the background free hole concentration and electron trap density, yielding a long electron diffusion length of 2.72 ± 0.15 μm. It increases the optimized thickness of narrow-bandgap perovskite films to 1000 nm, yielding exceptional stabilized efficiencies of 20.2 and 22.7% for single junction narrow-bandgap PSCs and monolithic perovskite-perovskite tandem cells, respectively. This work provides a promising method to enhance the optoelectronic properties of narrow-bandgap perovskites and unleash the potential of perovskite-perovskite tandem solar cells.
关键词： narrow-bandgap perovskites,perovskite solar cells,tandem solar cells,electron diffusion length,cadmium ions
更新于2025-09-16 10:30:52
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Three-Terminal Tandem Solar Cells With a Back-Contact-Type Bottom Cell Bonded Using Conductive Metal Nanoparticle Arrays
摘要： To address three-terminal tandem solar cells composed of a back-contact-type Si bottom cell, which, in principle, has a tolerance against spectral variation, we fabricate the three-terminal GaAs/Si tandem device bonded using conductive metal nanoparticle arrays and measure the power extraction. A power equivalent to the sum of the power generated by the top and bottom subcells is extracted even under varying spectral conditions, which indicates advantages in three-terminal tandem solar cells with a back-contact-type bottom cell for terrestrial applications.
关键词： Back-contact-type bottom cells,terrestrial applications,spectral variation,three-terminal tandem solar cells
更新于2025-09-16 10:30:52
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Large Area 23%-Efficient Monolithic Perovskite/Homo-Junction-Silicon Tandem Solar Cell With Enhanced UV Stability Using Down-Shifting Material
摘要： UV induced degradation and parasitic ultraviolet (UV) absorption by the 'sun-facing' carrier transport layer in a perovskite cell hinders stability and electrical performance when the perovskite cell is a top cell for a Si-based tandem. In this work, we tackle these issues by applying textured polydimethylsiloxane (PDMS) films that incorporate a down-shifting material (Ba,Sr)2SiO4:Eu2+ micron phosphor on the front of monolithic perovskite/silicon tandem cells. This film serves multiple purposes: antireflective control for the top cell, light trapping in the Si cell as well as absorbing UV and re-emitting green light with high quantum yield. When applied onto a 4 cm2 monolithic perovskite/silicon tandem solar cell, the power conversion efficiency was improved from 20.1% (baseline device without any anti-reflective film) to 22.3% (device with anti-reflective film but without the phosphors) and to 23.1% (device with down-shifting and antireflective film). The steady-state efficiency of 23.0% and a high FF of 81% achieved by the champion device are the highest values to date for a monolithic perovskite/Si tandem that uses homo-junction-silicon bottom cell. Moreover, results of continuous UV irradiation test show that this composite down-shifting antireflection film significantly enhances the UV stability for the tandem device. This work demonstrates an elegant approach for improving the efficiency and stability for larger area perovskite/silicon tandems.
关键词： perovskite/silicon tandem solar cells,down-shifting material,efficiency improvement,polydimethylsiloxane (PDMS),UV stability
更新于2025-09-16 10:30:52
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Modeling and implementation of tandem polymer solar cells using wide‐bandgap front cells
摘要： Tandem device architectures offer a route to greatly increase the maximum possible power conversion efficiencies (PCEs) of polymer solar cells, however, the complexity of tandem cell device fabrication (such as selecting bandgaps of the front and back cells, current matching, thickness, and recombination layer optimization) often result in lower PCEs than are observed in single‐junction devices. In this study, we analyze the influence of front cell and back cell bandgaps and use transfer matrix modeling to rationally design and optimize effective tandem solar cell structures before actual device fabrication. Our approach allows us to estimate tandem device parameters based on known absorption coefficients and open‐circuit voltages of different active layer materials and design devices without wasting valuable time and materials. Using this approach, we have investigated a series of wide bandgap, high voltage photovoltaic polymers as front cells in tandem devices with PTB7‐Th as a back cell. In this way, we have been able to demonstrate tandem devices with PCE of up to 12.8% with minimal consumption of valuable photoactive materials in tandem device optimization. This value represents one of the highest PCE values to date for fullerene‐based tandem solar cells.
关键词： tandem solar cells,polymer solar cells,solar cells
更新于2025-09-12 10:27:22
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Vacuum‐Assisted Growth of Low‐Bandgap Thin Films (FA <sub/>0.8</sub> MA <sub/>0.2</sub> Sn <sub/>0.5</sub> Pb <sub/>0.5</sub> I <sub/>3</sub> ) for All‐Perovskite Tandem Solar Cells
摘要： All-perovskite multijunction photovoltaics, combining a wide-bandgap (WBG) perovskite top solar cell (EG ≈1.6–1.8 eV) with a low-bandgap (LBG) perovskite bottom solar cell (EG < 1.3 eV), promise power conversion efficiencies (PCEs) >33%. While the research on WBG perovskite solar cells has advanced rapidly over the past decade, LBG perovskite solar cells lack PCE as well as stability. In this work, vacuum-assisted growth control (VAGC) of solution-processed LBG perovskite thin films based on mixed Sn–Pb perovskite compositions is reported. The reported perovskite thin films processed by VAGC exhibit large columnar crystals. Compared to the well-established processing of LBG perovskites via antisolvent deposition, the VAGC approach results in a significantly enhanced charge-carrier lifetime. The improved optoelectronic characteristics enable high-performance LBG perovskite solar cells (1.27 eV) with PCEs up to 18.2% as well as very efficient four-terminal all-perovskite tandem solar cells with PCEs up to 23%. Moreover, VAGC leads to promising reproducibility and potential in the fabrication of larger active-area solar cells up to 1 cm2.
关键词： vacuum-assisted growth control,all-perovskite tandem solar cells,solar cells,large grain,low-bandgap perovskites
更新于2025-09-12 10:27:22
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Perovskite/c-Si Monolithic Tandem Solar Cells Under Real Solar Spectra: Improving Energy Yield by Oblique Incident Optimization
摘要： Many research groups have noticed the performance of rapidly-developed perovskite/silicon monolithic tandem solar cells (TSCs) under real situation, but they overlook the short-current density mismatch of two sub-cells at different times in a day and the spectrum variation at different latitudes. Here we have systematically analyzed the efficiency losses and proposed optimization scheme by combination of experiment and simulation relying on reliable experimental data in a year. We have verified the simulated absorptance spectra varying with incident angle θ to substitute the external quantum efficiency spectra, which makes the optimization at oblique incidence possible. More importantly, we have further calculated and expanded the optimized current losses and energy output enhancement in perovskite/silicon monolithic TSCs to all latitudes. This work can be served as a practical guidance for the design of perovskite/silicon monolithic TSCs with the best annual energy output at different latitudes in the world.
关键词： Perovskite/silicon monolithic tandem solar cells,real solar spectra,efficiency losses,oblique incident optimization,energy yield
更新于2025-09-12 10:27:22
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Two‐terminal Perovskite silicon tandem solar cells with a high‐Bandgap Perovskite absorber enabling voltages over 1.8?V
摘要： Perovskite silicon tandem solar cells are a promising technology to overcome the efficiency limit of silicon solar cells. Although highest tandem efficiencies have been reported for the inverted p‐i‐n structure, high‐efficiency single junction perovskite solar cells are mostly fabricated in the regular n‐i‐p architecture. In this work, regular n‐i‐p perovskite solar cells with a high‐bandgap mixed cation mixed halide absorber suitable for tandem solar cells are investigated by compositional engineering and the open‐circuit voltage is improved to over 1.12 V using a passivating electron contact. The optimized perovskite solar cell is used as a top cell in a monolithic perovskite silicon tandem device with a silicon heterojunction bottom cell allowing for voltages up to 0.725 V. The tandem solar cells with an active area of 0.25 cm2 achieve record open‐circuit voltages of up to 1.85 V and have efficiencies over 20%. Analyzing the perovskite absorber by spatially resolved photoluminescence measurements shows a homogenous and stable emission at ~ 1.7 eV which is an optimal value for tandem applications with silicon. The tandem solar cells are mainly limited due to a low current. A spectrometric characterization reveals that the perovskite solar cell is current limiting which could be improved by a thicker perovskite absorber.
关键词： spectrometric characterization,high‐bandgap perovskite absorber,perovskite silicon tandem solar cells
更新于2025-09-12 10:27:22
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Enhancing PbS Colloidal Quantum Dot Tandem Solar Cell Performance by Graded Band Alignment
摘要： Colloidal quantum dot solids are attractive candidates for tandem solar cells because of their widely tunable bandgaps. However, the development of quantum dot tandem solar cell has lagged far behind that of its single-junction counterpart. One of the fundamental problems with colloidal quantum dot solar cells is the relatively small diffusion length, which limits the quantum dot absorbing layer thickness and hence the power conversion efficiency. In this research, guided by optical modelling and utilising a graded band alignment strategy, a two-terminal monolithic solution-processed quantum dot tandem solar cell has been successfully fabricated and a power conversion efficiency of 6.8% has been achieved. The band grading approach utilised the complementary tuning of work functions and band alignment through judicious choices of the nanoparticle surface chemistry and quantum dot confined size. This work demonstrates a general approach to improving the efficiency for tandem thin film solar cells.
关键词： tandem solar cells,optical modelling,Colloidal quantum dot solids,graded band alignment,power conversion efficiency
更新于2025-09-11 14:15:04
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AIP Conference Proceedings [AIP Publishing 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Fes, Morocco (25–27 March 2019)] 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Electrical and optical analysis of a spray coated transparent conductive adhesive for two-terminal silicon based tandem solar cells
摘要： This work presents the results of the electrical and optical characterization of a new transparent conductive adhesive (TCA) that combines the techniques of spray pyrolysis and a sol-gel like process. This approach is of particular interest since the adhesive itself forms both the electrical and the mechanical interconnection of the bonded sub-cells. The electrical and optical characterization of the developed TCA shows a minimum connecting resistivity of 17 ?cm2 and a simulated reflection at the Si-TCA interface of ≈ 20%. By coating both substrate surfaces with a TiO2 anti reflection coating (ARC), the reflectance at the Si-TCA interface was successfully reduced down to <5%. The efficiency potential of a glued dual junction device was simulated in dependence of the electrical and optical properties of the TCA. The reported values of 17 ?cm2 connecting resistivity and 20% reflection limit the device efficiency to 22.3% (71% of the maximum achievable efficiency). Reducing the reflection to below 5%, as practically demonstrated in this paper, allows to increase this value to 25.3% (>80% of maximum), while additionally reducing the connecting resistivity to 10 ?cm2 or 1 ?cm2 allows for a further increase to 27.3% and 30.0%, respectively.
关键词： reflection losses,sol-gel process,tandem solar cells,connecting resistivity,TiO2 anti reflection coating,electrical characterization,transparent conductive adhesive,optical characterization,spray pyrolysis
更新于2025-09-11 14:15:04
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The Value of Efficiency in Photovoltaics
摘要： Here, we introduce the value of efficiency (VOE), a metric that determines the maximum allowable cost for an innovation to improve the levelized cost of electricity. We use this metric to analyze historic, regional, and technological trends. We find indications for a stronger regional and sectoral market diversification. One example is tandem solar cells that could help to reduce electricity costs in US residential installations. We highlight the need for new PV technologies, like perovskites, to match leading technology degradation rates.
关键词： perovskites,value of efficiency,degradation rates,tandem solar cells,photovoltaics
更新于2025-09-11 14:15:04