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The Sn–Pb mixed perovskite with a narrow bandgap is essential for the construction of all‐perovskite tandem solar cells. However, the oxidation of Sn2+ to Sn4+ makes the fabrication of Sn–Pb perovskite solar cells (PSCs) challenging. Herein, a ferrocene (Fc) capping layer is introduced on the surface of Sn–Pb mixed perovskite to maintain a reducing environment. This is due to a strong electron supply capacity from the π‐orbitals in cyclopentadiene in Fc, which effectively suppresses the oxidation of Sn2+, reduces the defect density, and leads to an improvement in carrier lifetime. Therefore, the Fc capping layer significantly improves the power conversion efficiency (PCE) of single‐junction Sn–Pb PSCs from 17.49% to 21.02%. It maintains 87% of its initial PCE after light exposure at 1 sun condition in N2 atmosphere for 288 h, demonstrating good long‐term stability. The strategy outlined herein offers a straightforward and efficient approach to enhance the stability and PCE of narrow‐bandgap Sn–Pb mixed PSCs. [ABSTRACT FROM AUTHOR]

At present, one of the major factors limiting the further improvement of inverted (p‐i‐n) perovskite solar cells (PSCs) is trap‐assisted non‐radiative recombination at the perovskite/electron transporting layer (ETL) interface. Surface passivation with organic ammonium salt is a powerful strategy to improve the performance of PSCs. Herein, an effective method by using propylamine hydroiodide (PAI) and 1,3‐diaminopropane dihydroiodide (PDADI) is reported to modify the perovskite/ETL interface. These two ammonium salts do not form new perovskite but directly passivate the defects on the perovskite surface after annealing. The results show that the PDADI‐modified perovskite films possess a lower surface defect density and less non‐radiative recombination as well as improved charge carrier transport. Based on this strategy, the PDADI‐modified p‐i‐n PSCs deliver an impressive efficiency of 25.09% (certified 24.58%) with an open‐circuit voltage of 1.184 V. Furthermore, the unencapsulated PDADI‐modified PSCs also exhibit good storage stability, retaining 91% of initial PCE at 65 °C in a N2 glove box for 1300 h. This strategy provides an efficient route to fabricate highly efficient and stable inverted p‐i‐n structured PSCs. [ABSTRACT FROM AUTHOR]

Thermal evaporation can significantly facilitate scalable, uniform, and conformal perovskite film, particularly well‐suited for the preparation of perovskite/silicon (Si) tandem solar cells. However, the perovskite material easily induces a phase transition from a photoactive phase to a photoinactive phase, limiting the development of the stability and efficiency of tandem cells. Introducing lead chloride (PbCl2) into wide‐bandgap perovskite materials is beneficial for the fabrication of efficient and stable light‐absorbing materials, but the microscopic mechanism of the effect of PbCl2 on perovskite is still unclear. The study here reports evidences that the addition of PbCl2 to improve perovskite film stability and optoelectronic performance is due to the minor octahedral tilting of the perovskite structure are reported. It also demonstrates that this strategy accelerates interfacial charge transfer and carrier diffusion in the perovskite bulk and heterojunction interfaces. Therefore, the wide‐bandgap perovskite solar cells (PSCs) prepared by adding PbCl2 exhibit a champion power conversion efficiency (PCE) of 17.80%. The PSCs retain 97% of their performance following 200 h of operation at the maximum power point under full 1‐sun illumination. Finally, monolithic perovskite/Si tandem cells with record PCEs of 27.43% and an open‐circuit voltage of 1.817 V are fabricated. [ABSTRACT FROM AUTHOR]

Elpasolite Cs2AgBiBr6 also known as double perovskite has been touted in recent years as a promising alternative to the lead‐based perovskite for light harvesting. Its structure and properties mainly stem from the replacement of Pb2+ cation with a pair of aliovalent silver (Ag+) and bismuth (Bi3+) cations. Although the elpasolite Cs2AgBiBr6 exhibits improved stability, its photophysical properties and device performance are inferior to those of the Pb‐based perovskites. To date, numerous efforts have been geared toward the development of efficient Cs2AgBiBr6 solar cells. However, the indirect, wide bandgap and high exciton binding energy of Cs2AgBiBr6 have limited such efforts. This has been attributed to its low (zero) electronic dimensionality (0D), formation of small polaronic states, and interfacial imperfections with charge transporting layers. In this review, the different aspects of the elpasolite Cs2AgBiBr6 in relation to compositional and interlayer interactions in solar cell are discussed, and its suitability for photovoltaic application is assessed, accompanied by potential measures to further advance its performance. An alternate application of Cs2AgBiBr6 in photocatalysis, which takes advantage of its less toxicity and better stability, is also discussed. [ABSTRACT FROM AUTHOR]

Metal‐halide perovskite solar cells (PSCs) exhibit outstanding power conversion efficiencies (PCEs) when fabricated as mm‐sized devices, but creation of high‐performing large‐area modules that are stable on a sufficiently long timescale still presents a significant challenge. Herein, the quality of large‐area perovskite film is improved by using ionic liquid additives via forming a new Pb‐N bonding between the ionic liquid and Pb2+. This new bond can be modulated by a critical screening of the anion structure of the ionic liquid. The selected ionic liquid effectively reduces the defects of the perovskite films and markedly elongate their carrier lifetimes. As a result, a champion PCE of 24.4% for small‐area (0.148 cm2) devices and 20.4% for larger‐area (10.0 cm2) modules under AM 1.5G irradiation is achieved. More importantly, the modified devices retain 90% of their peak PCE after aging for 1900 h at 65 ± 5 °C (ISOS‐T‐1) and 80% after continuous light soaking for 750 h. The non‐encapsulated modules maintained 80% of their peak PCE after 1100 h of aging in the air with a relative humidity of 35 ± 5% and temperature of 25 ± 5 °C under dark (ISOS‐D‐1), showing great potential for future commercialization. [ABSTRACT FROM AUTHOR]

Semiconductor quantum dots (QDs) are nanocrystals whose excitons are bound in 3D space. Owning to their remarkable quantum confinement effect, QDs exhibit a discontinuous electronic energy level structure similar to that of atoms, leading to novel physical, optical, and electrical properties for various optoelectronic device applications including solar cells. Near‐infrared photoactive narrow bandgap (NBG) QDs can maximize the use of solar energy through the quantum size effect, offering a good opportunity for designing highly efficient wide‐spectrum responsive solar cells. This review analyzes the recent research progress of NBG QDs as light absorbing materials in solar cells. The critical elaboration of the latest achievements both in material design and device optimization for NBG QD‐based solar cells (QDSCs), including QD synthesis and film fabrication, design of device configuration, classification of NBG QDs and their photovoltaic performance, strategies for performance improvements is focused upon. The current challenges and perspectives for the further advance of NBG QDSCs are also discussed. [ABSTRACT FROM AUTHOR]