Defect passivation is an effective method to improve the performance of perovskite solar cells. In this study, four phenethylammonium iodides featuring different functional groups directly linking to the benzene ring are introduced on the surface of perovskite films ((FAPbI3)1–x (MAPbBr3–y Cl y ) x ) to investigate their passivation effects. It is found that the electron density of the benzene ring has significant influence on the interfacial passivation: phenethylammonium iodide with electron-donating groups (methoxyl and methyl) present favorable passivation effects, while the salt with electron-withdrawing group (nitro) delivers undesirable impacts. The passivation is attributed to the electrostatic interaction between the benzene ring and the undercoordinated Pb2+ ions. The salt-treated films are employed to fabricate solar cells, and an efficiency of 22.98% is achieved. In addition, the treated device shows good long-term stability for 1000 h of storage in a dark, ambient environment.

Summary An efficient electron transport layer (ETL) between the perovskite absorber and the cathode plays a crucial role in obtaining high-performance planar perovskite solar cells (PSCs). Here, we incorporate 2,2,2-trifluoroethanol (TFE) in the commonly used tin oxide (SnO 2 ) ETL, and it successfully improves the power conversation efficiency (PCE) and suppresses the hysteresis of the PSCs: the PCE is increased from 19.17% to 20.92%, and the hysteresis is largely reduced to be almost negligible. The origin of the enhancement is due to the improved electron mobility and optimized work function of the ETL, together with the reduced traps in the perovskite film. In addition, O 2 plasma is employed to treat the surface of the TFE-incorporated SnO 2 film, and the PCE is further increased to 21.68%. The concept here of incorporating organic small molecules in the ETL provides a strategy for enhancing the performance of the planar PSCs.

This article presents a simple and effective method of functionalizing hydrogen‐terminated silicon (Si) nanocrystals (NCs) to form a high‐quality colloidal Si NC ink with short ligands that allow charge transport in nanocrystal solid films. Si NCs fabricated by laser‐pyrolysis and acid etching are passivated with allyl disulfide via ultraviolet (UV)‐initiated hydrosilylation to form a stable colloidal Si NC ink. Then a Si NC‐based photodiode is directly fabricated in air from this ink. Only a solution‐processed poly(3,4‐ethylenedioxy‐thiophene):poly(styrene sulfonate) (PEDOT: PSS) electron blocking layer and top‐ and bottom‐contacts are needed along with the Si NC layer to construct the device. A Schottky‐junction at the interface between the Si NC absorber layer and aluminum (Al) back electrode drives charge separation in the device under illumination. The unpackaged Si NC‐based photodiode exhibites a peak photoresponse of 0.02 A W−1 to UV light in air, within an order of magnitude of the response of commercially available gallium phosphide (GaP), gallium nitride (GaN), and silicon carbide (SiC) based photodetectors. This provides a new pathway to large‐area, low‐cost solution‐processed UV photodetectors on flexible substrates and demonstrates the potential of this new silicon nanocrystal ink for broader applications in solution‐processed optoelectronics.