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Comprehensive Summary: Inverted perovskite solar cells (PerSCs) are a highly promising candidate in the photovoltaic field due to their low‐temperature fabrication process, negligible hysteresis, and easy integration with Si‐based solar cells. A cathode interlayer (CIL) is necessary in the development of inverted devices to reduce the trap density and energy barrier between the electron transport layer (ETL) and the electrode. However, most CILs are highly thickness‐sensitive due to low conductivity and poor film‐forming. In this study, we report on a self‐doping perylene imide‐based ionene polymer (PNPDIN) used as CIL material to modify electrode in inverted PerSCs. PNPDIN exhibits high conductivity and a good solubility in polar solvent, which results in an improved power conversion efficiency (PCE) from 10.05% (device without a CIL) to 16.97%. When the blend of PNPDIN and Bphen was used as a mixed CIL, the PCE of PerSCs can be further increased to 21.28% owing to the excellent morphology and matched energy level. More importantly, the PCE of the device is highly tolerant to the thickness of the mixed CIL, which benefited from the high conductivity of PNPDIN. This development is expected to provide an excellent mixed CIL material for roll‐to‐roll processing efficient and stable inverted PerSCs. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Inverted perovskite solar cells (PerSCs) are a highly promising candidate in the photovoltaic field due to their low‐temperature fabrication process, negligible hysteresis, and easy integration with Si‐based solar cells. A cathode interlayer (CIL) is necessary in the development of inverted devices to reduce the trap density and energy barrier between the electron transport layer (ETL) and the electrode. However, most CILs are highly thickness‐sensitive due to low conductivity and poor film‐forming. In this study, we report on a self‐doping perylene imide‐based ionene polymer (PNPDIN) used as CIL material to modify electrode in inverted PerSCs. PNPDIN exhibits high conductivity and a good solubility in polar solvent, which results in an improved power conversion efficiency (PCE) from 10.05% (device without a CIL) to 16.97%. When the blend of PNPDIN and Bphen was used as a mixed CIL, the PCE of PerSCs can be further increased to 21.28% owing to the excellent morphology and matched energy level. More importantly, the PCE of the device is highly tolerant to the thickness of the mixed CIL, which benefited from the high conductivity of PNPDIN. This development is expected to provide an excellent mixed CIL material for roll‐to‐roll processing efficient and stable inverted PerSCs. [ABSTRACT FROM AUTHOR]

It is still a challenge to prepare 2D ultrathin ZnO in a simple method, especially for the in‐situ growth of 2D ultrathin ZnO on different substrates. Herein the ZnO foam with high specific surface area is successfully assembled in situ from graphene‐like ultrathin nanosheet on various substrates, including rigid fluoride doped tin oxide, Ni foam, and flexible indium tin oxide, carbon cloth, etc. The thickness of graphene‐like nanosheet is just ≈1.5 nm. The results reveal that the specific surface area of ZnO nanosheets is 90.7 m2 g−1. The high specific surface area of the hydrophilic ZnO foam and its in‐situ growth characteristic make it promising water channel in solar‐driven interfacial water evaporation system. By using a flexible carbon cloth/ZnO foam (C‐ZnO) Janus absorber, a high rate of water evaporation (2.4 kg m−2 h−1), which is 4.6 times higher than that of natural evaporation is demonstrated. This work provides a new method in the design of ZnO ultrathin nanosheets, what's more, the facile growth of the ZnO foam on various substrates make it possible for the application in optoelectronic devices. [ABSTRACT FROM AUTHOR]