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Improving power conversion efficiency (PCE) is important for broadening the applications of organic photovoltaic (OPV) cells. Here, a maximum PCE of 19.0% (certified value of 18.7%) is achieved in single-junction OPV cells by combining material design with a ternary blending strategy. An active layer comprising a new wide-bandgap polymer donor named PBQx-TF and a new low-bandgap non-fullerene acceptor (NFA) named eC9-2Cl is rationally designed. With optimized light utilization, the resulting binary cell exhibits a good PCE of 17.7%. An NFA F-BTA3 is then added to the active layer as a third component to simultaneously improve the photovoltaic parameters. The improved light unitization, cascaded energy level alignment, and enhanced intermolecular packing result in open-circuit voltage of 0.879 V, short-circuit current density of 26.7 mA cm-2 , and fill factor of 0.809. This study demonstrates that further improvement of PCEs of high-performance OPV cells requires fine tuning of the electronic structures and morphologies of the active layers.
Cui et al. (Tue,) studied this question.