High performance ternary organic solar cells using two miscible donor molecules based on PTB7-Th and DR3TBDTT

Abstract

The recent stunning rise in power conversion efficiencies (PCEs) of ternary organic solar cells (OSCs) has triggered much attention. However, achieving high PCE values are quite challenging because the ternary system is complicated on phase separation behavior. In this work, ternary organic solar cells (OSCs) with one acceptor (PC71BM) and two donors, i.e., one polymer (PTB7-Th) and one small molecule (DR3TBDTT) have been fabricated. We substantially improved PCE from the best reported value of 7.53%–9.25% with increase of 22.8%, and an averaged PCE of 9.25% is obtained due to the improvement of the fill factor (FF) and the short-circuit current density (Jsc). The results of atomic force microscopy (AFM) indicate that a highly ordered molecular compatibility could be obtained by forming alloy with two miscible donors, and the doping of DR3TBDTT not only protects the long distance charge transport in the original binary system, but also improves the size of phase separation of the active layer within the ternary OSCs, thus forming the ordered nano morphology, which can improve the mobility of hole and reduce the charge recombination.