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Indolocarbazole-based Small Molecules as Guest Donors for High-performance Ternary Organic Photovoltaics
Hsiao Han Chiu, Bing-Huang Jiang, Hong Chi Wang, Xuan-Ming Su, Yu-Hsuan Kang, Yu-Wei Su, Hui-Shan Shih, Chih-Ping Chen*, Yuan Jay Chang*
This study explores the use of A-D-A or A-D-A′-type small molecule donors that contain an indolocarbazole-based moiety with both symmetric and asymmetric structures as the third component in PM6:Y6 systems to develop ternary organic photovoltaics (OPVs). The guest donor, Ema-OEt, was found to be highly miscible with Y6, resulting in an optimized morphology of an alloy-like structure in the blended film. This, in turn, led to balanced charge transport, high charge mobility, and low charge recombination in the devices, resulting in a synergistic improvement in PV parameters, ultimately leading to an advanced power conversion efficiency (PCE) of 17.64 % in the optimized (PM6:Ema-OEt:Y6 = 1: 0.07: 1.2) ternary device. Furthermore, despite having a higher HOMO energy level than PM6, Ema-OEt, doped as a guest donor in the ternary OPV device, demonstrated a remarkable indoor PCE of 28.67 % under TL84 (Pin = 311.9 μW cm−2). These findings provide an effective and innovative approach to enhance the performance of OPVs.