Fine-tuning of non-fullerene acceptor gives over 14% efficiency for organic solar cells

Abstract

In this work, a new non-fullerene electron acceptor (Y8) was synthesized with a fused dithienothiophen [3, 2-b] -pyrrolo benzothiadiazole (TPBT unit with a BT-core) as central unit and two electron-deficient units of 2-(6-fluoro-2, 3-dihydro-3-oxo-1H-inden-1-ylidene) - propanedinitrile (F-IC) as the end groups. Y8 possessed strong absorption in 700–900 nm. The inverted device based on ITO/ZnO/PM6:Y8/MoO3/Ag structure, demonstrated the power conversion efficiency (PCE) up to 14.25% with a short circuit current density (Jsc) of 22.18 mA cm−2 and a high open-circuit voltage (Voc) of 0.88 V. And the optimized device based on PM6:Y8 exhibited relatively high electron mobility (8.7 × 10−4 cm2V−1s−1). These results demonstrated that application of F-IC end group based on small molecule could be a promising measure for improving efficiency of OPVs.