14.46% Efficiency small molecule organic photovoltaics enabled by the well trade-off between phase separation and photon harvesting

Abstract

Small molecule organic photovoltaics (SMPVs) were prepared by utilizing liquid crystalline donor material BTR-Cl and two similar optical bandgap non-fullerene acceptor materials BTP-BO-4F and Y6. The BTP-BO-4F and Y6 have the similar optical bandgap and different absorption coefficients. The corresponding binary SMPVs exhibit different short circuit current density (JSC) (20.38 vs. 23.24 mA cm−2), and fill factor (FF) (70.77% vs. 67.21%). A 14.46% power conversion efficiency (PCE) is acquired in ternary SMPVs with 30 wt% Y6, companied with a JSC of 24.17 mA cm−2, a FF of 68.78% and an open circuit voltage (VOC) of 0.87 V. The improvement on PCE of ternary SMPVs should originate from the well trade-off between phase separation and photon harvesting of ternary active layers by incorporating 30 wt% Y6 in acceptors. This work may deliver insight onto the improved performance of SMPVs by superposing the superiorities of binary SMPVs with similar optical bandgap acceptors into one ternary cell.