Synthesis of small molecule dye additive for efficient and DIO-free ternary organic solar cells

Abstract

A promising technique to enhance absorption of light in organic solar cells, “ternary approach” represents an important function in improving the device performance. We combined one small molecule dye (5,8-di(benzofuran-2-yl)-2,3-diphenylquinoxaline) (DB-Qx) with [6, 6]-phenyl C71 butyric acid methyl ester (PC71BM) (as the electron acceptor) and poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiopheneco-3-fluorothieno[3,4-b]thiophene-2-carboxylate] (PTB7-Th)(as the electron donor polymer) to form ternary solar cells. The morphology of the active layer of the ternary blend and hole mobility was potentially enhanced by the addition of a molecular donor. The complementary absorption of the two donors and matching photo-luminesce overlapping of DB-Qx with PTB7-Th contributed to improving the device performance. This means that the molecular donor in the ternary blend has an active function in the morphology. The devices produced PCE of 8.64% in the ternary blend system relative to 5.98% in the binary blend system. And, since the emission of DB-Qx partially overlaps with the absorption of PTB7Th, the transfer of energy from DB-Qx to PTB7-TH can improve the exciton utilization efficiency and achieve enhanced overall power conversion efficiency in this ternary solar cell. In this study, we synthesized a small fluorescent molecule material and constructed efficient ternary blend PSCs. Remarkably, the inverted device DIO-free ternary solar cells boost PCE from 5.98 to 8.64% and also exhibit the combined improvement in JSC and the morphology compared to those of DIO-processed films.