Construction of Effective Polymer Solar Cell Using 1,7-Disubstituted Perylene Diimide Derivatives as Electron Transport Layer

Abstract

The poor compatibility of an inorganic electron transport layer with the active layer and an ultrathin film organic material becomes a great obstacle in producing high-quality polymer solar cells with high-throughput roll-to-roll (R2R) method. Novel effective polymer solar cells had been fabricated by introducing 1, 7-disubstituted perylene diimide derivatives PDIH, PDIC, and PDIN as an electron transporting layer. It was noteworthy that PDIN could obviously improve the power conversion efficiency of solar cells that incorporated a photoactive layer composed of poly[(3-hexylthiophene)-2, 5-diyl] (P3HT) and the fullerene acceptor [6, 6-phenyl-C71-butyric acid methyl ester] (PC71BM). The power conversion efficiency varies from 1.5% for ZnO transparent cathode-based solar cells to 2.1% for PDIN-based electron transport layer-free solar cells. This improved performance could be attributed to the following reasons: the interaction between N atom in PDIN and O atom in indium tin oxide (ITO) reduced the work function of ITO, increased the built-in electric field, and thus lowered the electron transport barrier and improved the electron extraction ability of cathode, the appropriate roughness of the active layer increased the contact area with anode interfacial layer and enhanced the hole transport efficiency. These experimental results revealed that PDIN can be a promising novel effective material with a simplified synthesis process and lower cost as an electron transporting layer.