Enhanced performance of inverted polymer solar cells by adding benzyl viologen dichloride into ZnO electron transport layer

Abstract

An organic-inorganic hybrid electron transport layer (ETL) is developed using benzyl viologen dichloride (BV–2Cl) as a dopant for the preparation of sol-gel ZnO precursor solution. The inverted polymer solar cells (I–PSCs) based on PTB7-Th:PC71BM were prepared by introducing hybrid ZnO:BV-2Cl as ETL, and the effect of BV-2Cl on the photovoltaic performance of PSCs was closely investigated. Consequently, the device with hybrid ZnO:BV-2Cl (1% wt%) as ETL achieves the power conversion efficiency (PCE) of 9.31%, which is 16.5% more efficient than the device using pure ZnO as ETL. As the results indicate, hybrid ZnO:BV-2Cl films can modulate the interfacial compatibility of the hydrophilic surface of conventional ZnO films, hence enhancing charge transport and exciton dissociation. Our results indicate that using BV-2Cl as a dopant for the preparation of ZnO ETL is a facile and efficient method of fabricating high-performance I–PSCs.