Enhanced Charge Generation and Transport by Incorporating a Benzotriazole Unit for Low-Cost and High-Efficiency Organic Solar Cells

The photovoltaic performance of organic solar cells (OSCs) has reached the threshold for industrial applications, but the cost of most high-performance organic photovoltaic molecules is too high to meet the needs of industrialization. Herein, two low-cost thiophene-alt-quinoxaline (TQ)-based polymers, PTQ16-10 and PTQ16-20, are designed and synthesized by incorporating a benzotriazole (BTA) unit into the PTQ10 backbone, with the consideration of expanding the chemical modifiability of PTQ10 and thus optimizing its photovoltaic properties. The incorporation of BTA induces improved light absorption, up-shifted energy levels, more orderly molecular π-π packing, enhanced molecular crystallinity, and better charge transport capacity of the two polymers. Consequently, PTQ16-10:K2-based OSCs achieve enhanced charge generation and transport with faster and more efficient hole transfer, suppressed carrier recombination, and higher charge mobilities, resulting in an impressive power conversion efficiency (PCE) of 18.83%. Meanwhile, by introducing the second acceptor K6 into the PTQ16-10:K2 host blend, the ternary device achieves an excellent PCE of 19.52%, which is among the highest PCEs of OSCs based on low-cost photovoltaic materials. More importantly, this device is highly cost-effective for industrial-scale production, with an estimated minimum sustainable price of only 0.377 $ Wp-1 (Wp = peak-Watt), which is appreciably lower than that of reported high-performance OSCs. This work offers a rational guide in the development of low-cost and high-performance organic photovoltaic molecules and suggests the great potential of PTQ16-10 in cost-effective OSCs for industrialization.