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

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.