Solution-processing induced H-aggregate of Perylene-Diimide Zwitterion Exhibiting Compact Molecular Stacking toward Efficient Cathode Modification in Organic Solar Cells

Abstract

High-performance organic cathode interlayers (CILs) play a crucial role in the advance of organic solar cells (OSCs). However, organic CILs have exhibited inferior performances to their inorganic counterparts over a long time, due to the inherent shortcoming of poor charge transporting capability. Here, we designed and synthesized a perylene-diimide (PDI) zwitterion PDI-B as high-performance organic CIL for OSCs. We revealed that an obvious H-aggregate of PDI-B was formed during the solution processing, thereby significantly enhancing the charge transporting capability of the CIL. Compared to the classic PDINN, the π-π stacking distance of PDI-B was reduced from 4.2 Å to 3.9 Å, which further facilitated the charge transport. Consequently, PDI-B showed a high conductivity of 1.81×10−3S/m; this is comparable to that of inorganic CILs. The binary OSC showed an elevated PCE of 19.23%, which is among the highest PCE values for binary OSCs. Benefitting from improved solvent resistance and good compatibility with large-area processing method of PDI-B, the photovoltaic performances of inverted and 1-cm2 OSC were significantly improved. The results from this work provide a new approach of optimizing the condensed structure of PDI film to boost the charge conductivity, opening an avenue to develop high-performance PDI-based CILs.