Non-peripherally octaalkyl-substituted nickel phthalocyanines used as non-dopant hole transport materials in perovskite solar cells* *Project supported by the Shenzhen Overseas High-level Talents Innovation Plan of Technical Innovation (Grant No. KQJSCX20180323140712012) and the Major Program of Guangdong Basic and Applied Research (Grant No. 2019B121205001).

Abstract

This report presents two non-perihperally octaalkyl-substituted nickel phthalocyanines (NiPcs), namely, NiEt2Pc and NiPr2Pc, for use as dopant-free hole transport materials in perovskite solar cells (PSCs). The length extension of the alkyl chains from ethyl to propyl significantly tunes the NiPcs’ energy levels, thus reducing charge carrier recombination at the perovskite/hole transport layer (HTL) interface and leading to higher open-circuit voltage (V OC) and short-circuit current density (J SC) observed for the NiPr2Pc-based PSC. And higher charge carrier mobility, higher thin film crystallinity, and lower surface roughness of the NiPr2Pc HTL compared with that of the NiEt2Pc one also lead to higher J SC and fill factor (FF) observed for the NiPr2Pc-based device. Consequently, the NiPr2Pc-based PSC exhibits a higher power conversion efficiency (PCE) of 14.07% than that of the NiEt2Pc-based device (8.63%).