A feature of perovskite devices is their suitability in the fabrication of semitransparent solar cells (ST-SCs). Methylammonium lead iodide based perovskite material (MAPbI3 or PV) is a possible material of choice because of its semitransparent nature in thin film form and after considering a balance among average visible light transmittance (AVT), power conversion efficiency (PCE), and device stability. However, there are issues to be addressed in the design of PV ST-SCs, such as the stability of small grain crystals forming in thin films and reducing the number of layers in the device to increase AVT. We report herein that doping PV with a 0.03 wt % hybrid organic p-type semiconductor, fluorinated tetraarylbenzo [1,2- b:4,5- b']dipyrrol-1,5-yl alkanediylsulfonate salt (BDPSO), affords a device with a 280 nm active layer directly fabricated on an indium tin oxide/glass substrate, without fabricating a hole transporting layer. Such a device exhibited a 30% higher PCE of 16.9% than the device made without doping. This device exhibited a stable photocurrent output at the maximum power point (MPP) for >1000 s under air and an operational stability of retaining 93% of the initial PCE after 1000 h continuous light soaking at the MPP. The ST-SC devices made of BDPSO-doped 140 nm and 90 nm thick PV films and a 6 nm thick Au electrode achieved PCEs of 10.3 and 8.0% and whole device semitransparency values of 22 and 30% AVT, respectively. The origins of the observed doping effect of BDPSO are ascribed to the bissulfonate structure that can effectively passivate defects at the interface and grain boundaries and to the HOMO level matching with PV to facilitate charge transfer.
Keywords: doping; hole-transporting-layer-free; p-type semiconductor; perovskite solar cells; semitransparent; stability.