Recent progress in developing efficient monolithic all-perovskite tandem solar cells

Organic–inorganic halide perovskites have received widespread attention thanks to their strong light absorption,long carrier diffusion lengths,tunable bandgaps,and low temperature processing.Single-junction perovskite solar cells(PSCs)have achieved a boost of the power conversion efficiency(PCE)from 3.8%to 25.2%in just a decade.With the continuous growth of PCE in single-junction PSCs,exploiting of monolithic all-perovskite tandem solar cells is now an important strategy to go beyond the efficiency available in single-junction PSCs.In this review,we first introduce the structure and operation mechanism of monolithic all-perovskite tandem solar cell.We then summarize recent progress in monolithic all-perovskite tandem solar cells from the perspectives of different structural units in the device:tunnel recombination junction,wide-bandgap top subcell,and narrow-bandgap bottom subcell.Finally,we provide our insights into the challenges and scientific issues remaining in this rapidly developing research field.

Simultaneously enhanced moisture tolerance and defect passivation of perovskite solar cells with cross-linked grain encapsulation

The grain surfaces(film surface and grain boundary)of polycrystalline perovskite films are vulnerable sites in solar cells since they pose a high defect density and initiate the degradation of perovskite absorber.Achieving simultaneously defect passivation and grain protection from moisture is crucial for the viability of perovskite solar cells.Here,an in situ cross-linked grain encapsulation(CLGE)strategy that improves both device stability and defect passivation is reported.Cross-linkable semiconducting small molecules are mixed into the antisolvent to uniformly form a compact and conducting cross-linked layer over the grain surfaces.This cross-linked coating layer not only passivates trap states and facilitates hole extraction,but also enhances the device stability by preventing moisture diffusion.Using the CLGE strategy,a high power conversion efficiency(PCE)of 22.7%is obtained in 1.55-eV bandgap planar perovskite solar cells.The unencapsulated devices with CLGE exhibit significantly enhanced device stability again moisture and maintain>90%of their initial PCE after shelf storage under ambient condition for over10,000 h.

Ultrasensitive and stable X-ray detection using zero-dimensional lead-free perovskites

Sensitive and reliable X-ray detectors are essential for medical radiography,industrial inspection and security screening.Lowering the radiation dose allows reduced health risks and increased frequency and fidelity of diagnostic technologies for earlier detection of disease and its recurrence.Three-dimensional(3 D)organic-inorganic hybrid lead halide perovskites are promising for direct X-ray detection-they show improved sensitivity compared to conventional X-ray detectors.However,their high and unstable dark current,caused by ion migration and high dark carrier concentration in the 3 D hybrid perovskites,limits their performance and long-term operation stability.Here we report ultrasensitive,stable X-ray detectors made using zero-dimensional(0 D)methylammonium bismuth iodide perovskite(MA3Bi2I9)single crystals.The 0 D crystal structure leads to a high activation energy(Ea)for ion migration(0.46 e V)and is also accompanied by a low dark carrier concentration(~10^6 cm^-3).The X-ray detectors exhibit sensitivity of 10,620μC Gy-1 air cm-2,a limit of detection(Lo D)of 0.62 nG yairs-1,and stable operation even under high applied biases;no deterioration in detection performance was observed following sensing of an integrated X-ray irradiation dose of^23,800 m Gyair,equivalent to>200,000 times the dose required for a single commercial X-ray chest radiograph.Regulating the ion migration channels and decreasing the dark carrier concentration in perovskites provide routes for stable and ultrasensitive X-ray detectors.

The Main Progress of Perovskite Solar Cells in 2020-2021

Perovskite solar cells(PSCs)emerging as a promising photovoltaic technology with high efficiency and low manufacturing cost have attracted the attention from all over the world.Both the efficiency and stability of PSCs have increased steadily in recent years,and the research on reducing lead leakage and developing eco-friendly lead-free perovskites pushes forward the commercialization of PSCs step by step.This review summarizes the main progress of PSCs in 2020 and 2021 from the aspects of efficiency,stability,perovskite-based tandem devices,and lead-free PSCs.Moreover,a brief discussion on the development of PSC modules and its challenges toward practical application is provided.

Cross-linked hole transport layers for high-efficiency perovskite tandem solar cells

Perovskite tandem solar cells have recently received extensive attention due to their promise of achieving power conversion efficiency(PCE)beyond the limits of single-junction cells.However,their performance is still largely constrained by the widebandgap perovskite solar cells which show considerable open-circuit voltage(VOC)losses.Here,we increase the VOCand PCE of wide-bandgap perovskite solar cells by changing the hole transport layer(HTL)from commonly used poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine)(PTAA)to in-situ cross-linked small molecule N_(4),N_(4)′-di(naphthalen-1-yl)-N_(4),N_(4)′-bis(4-vinylphenyl)biphenyl-4,4′-diamine(VNPB).The stronger interaction and lower trap density at the VNPB/perovskite interface improve the PCE and stability of wide-bandgap perovskite solar cells.By using the cross-linked HTL for front wide-bandgap subcells,PCEs of 24.9%and 25.4%have been achieved in perovskite/perovskite and perovskite/silicon tandem solar cells,respectively.The results demonstrate that cross-linkable small molecules are promising for high-efficiency and cost-effective perovskite tandem photovoltaic devices.

Revealing the output power potential of bifacial monolithic all-perovskite tandem solar cells

Bifacial monolithic all-perovskite tandem solar cells have the promise of delivering higher output power density by inheriting the advantages of both tandem and bifacial architectures simultaneously.Herein,we demonstrate,for the first time,the bifacial monolithic all-perovskite tandem solar cells and reveal their output power potential.The bifacial tandems are realized by replacing the rear metal electrodes of monofacial tandems with transparent conduction oxide electrodes.Bandgap engineering is deployed to achieve current matching under various rear illumination conditions.The bifacial tandems show a high output power density of 28.51 mW cm−2 under a realistic rear illumination(30 mW cm−2).Further energy yield calculation shows substantial energy yield gain for bifacial tandems compared with the monofacial tandems under various ground albedo for different climatic conditions.This work provides a new device architecture for higher output power for all-perovskite tandem solar cells under real-world conditions.

A 2.16 eV bandgap polymer donor gives 16%power conversion efficiency

在宽带隙高分子给体材料中,带隙大于2.07 eV(起峰吸收小于600 nm)的超宽带隙给体由于具有出色的短波吸光特性,在三元有机太阳电池、叠层太阳电池中具有重要的应用价值,然而长期以来基于超宽带隙给体的电池效率低于13%.本文提出新的设计思路:采用烷氧基氟苯(FAB)构筑超宽带隙给体.一方面利用FAB的高芳香性拓宽带隙,另一方面利用FAB的"构象锁定"特性提高材料的迁移率,从而大幅提高超宽带隙给体的光伏性能.结果合成的高分子给体W1,其光学带隙达2.16eV,与小分子受体Y6共混制备的单结有机太阳电池效率达16.16%,这是目前超宽带隙给体电池的最高效率.

Low-temperature processed inorganic hole transport layer for efficient and stable mixed Pb-Sn low-bandgap perovskite solar cells

Metal halide perovskite solar cells(PSCs)have attracted tremendous attention as an emerging photovoltaic technology due to their high efficiency,low cost and ease of fabrication from earth-abundant materials[1,2].The power conversion efficiencies(PCEs)have been rapidly boosted from 3.8%in the pioneer’s work to a certified 24.2%nowadays in just ten years[3].The PCE breakthroughs in PSCs have mostly adopted full lead-based perovskites(APbX3)with bandgaps of 1.5–1.6 eV.

钙钛矿叠层太阳电池

自2009年报道以来,钙钛矿太阳电池的能量转换效率从3.8%增长到25.5%,是发展最为迅猛的一类太阳电池.为了进一步提高能量转换效率,突破肖克利·奎伊瑟效率极限(S-Q极限),可以采用带隙互补的吸光材料制备多结太阳电池,从而提高太阳光利用率.由于钙钛矿吸光材料具有可溶液加工、带隙可调的特性,它是制备叠层太阳电池的理想材料.本文介绍了近年来基于钙钛矿材料的高效叠层太阳电池:钙钛矿/硅,钙钛矿/铜铟镓硒,钙钛矿/钙钛矿和钙钛矿/有机叠层太阳电池.作者首先介绍了叠层电池的结构和工作原理,之后分别总结了以上四种叠层电池的重要进展,最后围绕器件结构、效率、大面积制备、稳定性、成本以及铅毒性这六个方面,讨论了未来钙钛矿叠层太阳电池面临的挑战.目前钙钛矿/硅、钙钛矿/铜铟镓硒和钙钛矿/钙钛矿叠层电池的能量转换效率分别达到了29.1%、25.9%和25.6%,均超过了相应单结电池的最高效率,有巨大发展空间.钙钛矿叠层太阳电池将会吸引越来越多的关注,成为太阳能研究领域的重要方向.

高效稳定锡基钙钛矿太阳电池

Astonishing progress on the stability and performance of lead halide perovskite solar cells(PSCs)has been achieved in the past few years.However,the presence of toxic lead in the perovskite composition still remains a major challenge for the large-scale deployment due to legislation and environment issues.A straightforward solution is to develop lead-free perovskite alternatives without sacrificing the excellent optical and electrical properties.Among all the lead-free alternatives,non-toxic Sn halide perovskites are the most promising since Sn has similar ionic radius to Pb.Sn-based perovskites display optical and electronic properties similar to their lead analogues,which offers high potential to achieve high performance.

CsPb(I_(x)Br_(1-x))_(3) solar cells

Owing to its nice performance, low cost, and simple solution-processing, organic-inorganic hybrid perovskite solar cell(PSC) becomes a promising candidate for next-generation high-efficiency solar cells.The power conversion efficiency(PCE) has boosted from 3.8% to 25.2% over the past ten years. Despite the rapid progress in PCE, the device stability is a key issue that impedes the commercialization of PSCs. Recently, all-inorganic cesium lead halide perovskites have attracted much attention due to their better stability compared with their organic-inorganic counterpart. In this progress report, we summarize the properties of CsPb(IxBr1-x)3 and their applications in solar cells. The current challenges and corresponding solutions are discussed. Finally, we share our perspectives on CsPb(IxBr1-x)3 solar cells and outline possible directions to further improve the device performance.

Vapor treatment enables efficient and stable FAPbI_(3) perovskite solar cells

Metal halide perovskite solar cells(PSCs)have attracted extensive research interest in recent years due to their lowcost processing,high power conversion efficiency(PCE),and tunable bandgap enabling tandem photovoltaics(PVs).Over the past decade,PSCs have witnessed an impressive increase in PCEs from 3.8%to 25.5%,which is the highest among thin-film PV technologies and is comparable to those of crystalline silicon solar cells[1].