Efficiency enhancement of organic solar cell by small molecule electrolyte based on naphthalene diimide as an electron transport layer

Abstract

As an electron transport layer (ETL) for organic solar cells (OSCs), a naphthalene diimide (NDI)-based alcohol-soluble small molecule electrolyte (FN-NDI-Br) was designed and synthesized. The small molecule electrolyte was synthesized from the quaternization of the amino-terminal group in the alkyl chain. A bulk heterojunction (BHJ)-based inverted OSCs with the ITO/ZnO/ETL/PTB7-Th:PC71BM/MoO3/Ag structure were fabricated. The power conversion efficiency (PCE) enhancement was achieved by inserting a small molecule electrolyte as the interlayer. The device performance of the device with the PTB7-Th and PC71BM blend as the photoactive layer and FN-NDI with acetic acid additive as ETL was enhanced over the device with pristine ZnO from 8.53% to 8.78%. The performance of the device was enhanced up to 9.16% by modifying the side chain functionality compared with the device with a FN-NDI interlayer.