A simple single-thiophene derivative assists efficient as-cast ternary organic solar cells through Förster resonance energy transfer

Developing ternary organic solar cells has been acknowledged as an effective method to improve the power conversion efficiency compared to the traditional binary counterparts. Therefore, developing low-cost third components is a “two birds one stone” strategy to synchronously realize high-performance ternary devices and reduce the material costs. In this work, a single-thiophene derivative (5E,5′E)-5,5′-(thiophene-2,5-diylbis(methaneylylidene))bis(3-ethylthiazolidine-2,4-dione) (TTZD) is designed and synthesized in a one-step process from low-cost raw materials. By incorporating 3 wt% TTZD into the PTB7-Th:IEICO-4F blends, ternary devices afforded promoted power conversion efficiency of 10.63%, higher than the 9.53% of the binary control. As investigated, blending appropriate amounts of TTZD negligibly disturbed the binary blend morphologies, but transferred supplemental photon energy to the host blends through the Förster resonance energy transfer process, resulting in enlarged photocurrent.