Indoloindole-Based Hole Transporting Material for Efficient and Stable Perovskite Solar Cells Exceeding 24 Power Conversion Efficiency

摘要

The new concept of hole transporting materials (HTMs) has inspiredresearchers to develop high-performing and stable perovskite solar cells(PSCs). In particular, small molecular organic semiconductors have beenextensively studied for HTM due to their high reproducibility and easysynthesis. In this work, a novel linear-type series of indoloindole (IDID)-basedhole transporting materials comprising a fluorinated IDID core(IDIDF) andmultiple thiophene rings is developed. The structure-property relationship inthe IDIDF derivatives is investigated systematically by changing the alkylposition and length of the backbone. The intrinsic properties of the materialare significantly different depending on the alkyl position of inner thiophenering. The optimized material exhibits improved solubility, favorable molecularpacking patterns, and superior hole mobility. The champion PSCs using theoptimum molecule, IDIDF2, yield a power conversion efficiency of 23.16% innon-doped and 24.24% in doped conditions, which represent one of thehighest performances in n-i-p planar device configuration. For the first time,the IDIDF2-based PSCs achieve outstanding thermal and moisture stabilitiesunder thermal aging (85 °C) and relative humidity of 85%, respectively, for1500 h.