Ultraviolet-light induced H+ doping in polymer hole transport material for highly efficient perovskite solar cells

Abstract

Poly(N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine) (PTPD) is an appropriate hole transporting material (HTM) in perovskite solar cells (PSCs) due to its simple fabrication process. However, the relatively low conductivity of PTPD compared with traditional inorganic HTMs limits its application in highly efficient PSCs. Here, we employ an ultraviolet (UV)-light induced H+ doping strategy to improve the conductivity of PTPD hole transporting layer (HTL) for high-performance n-i-p planar structure PSCs. The released proton (H+) from 4-isopropyl-4′-methyldiphenyliodonium tetrakis-(pentafluorophenyl-borate) (DPI-TPFB) induced by UV-light irradiation can coordinate with PTPD to form PTPD-NH+, which dramatically enhances the hole carrier transport and extraction. As a result, a champion power conversion efficiency (PCE) of 21.38% is achieved in PSCs with H+ doped PTPD as HTL, which is much higher than that (17.63%) of the PSCs with pristine PTPD HTL. Furthermore, the stability of the PSCs in humid air is significantly improved after adopting H+ doped PTPD to replace pristine PTPD, owing to the increased hydrophobicity of PTPD HTL.