A Thiadiazole-Based Conjugated Polymer With Ultradeep Homo Level And Strong Electroluminescence Enables 18.6% Efficiency In Organic Solar Cell

Under the premise of ensuring favorable bulk heterojunction morphology in organic solar cells (OSCs), conjugated polymer donors with deep-lying highest occupied molecular orbital (HOMO) levels are highly important to improve power conversion efficiencies (PCEs) by reducing photovoltage loss. However, the development of such materials has lagged. Herein, a thiadiazole-based conjugated polymer, PB2F is reported, which has a very deep HOMO level of -5.64 eV, and high electroluminescence quantum efficiency of 3.9 x 10(-3). In OSCs, the PB2F-based OSC gives an excellent PCE of 14.5% with an ultrahigh open-circuit voltage (V-OC) of 0.957 V by blending with an electron acceptor of IT-4F. More importantly, the PB2F as a third component is added into the PBDB-TF:BTP-eC9 blend to achieve an outstanding PCE of 18.6% (certified PCE 18.2%), which is one of the highest PCEs in OSCs.