Enhanced Charge\nGeneration and Transport by Incorporating\na Benzotriazole Unit for Low-Cost and High-Efficiency Organic Solar\nCells

The photovoltaic performance of organic solar cells (OSCs)\nhas\nreached the threshold for industrial applications, but the cost of\nmost high-performance organic photovoltaic molecules is too high to\nmeet the needs of industrialization. Herein, two low-cost thiophene-<i>alt</i>-quinoxaline (TQ)-based polymers, PTQ16–10 and\nPTQ16–20, are designed and synthesized by incorporating a benzotriazole\n(BTA) unit into the PTQ10 backbone, with the consideration of expanding\nthe chemical modifiability of PTQ10 and thus optimizing its photovoltaic\nproperties. The incorporation of BTA induces improved light absorption,\nup-shifted energy levels, more orderly molecular π–π\npacking, enhanced molecular crystallinity, and better charge transport\ncapacity of the two polymers. Consequently, PTQ16–10:K2-based\nOSCs achieve enhanced charge generation and transport with faster\nand more efficient hole transfer, suppressed carrier recombination,\nand higher charge mobilities, resulting in an impressive power conversion\nefficiency (PCE) of 18.83%. Meanwhile, by introducing the second acceptor\nK6 into the PTQ16–10:K2 host blend, the ternary device achieves\nan excellent PCE of 19.52%, which is among the highest PCEs of OSCs\nbased on low-cost photovoltaic materials. More importantly, this device\nis highly cost-effective for industrial-scale production, with an\nestimated minimum sustainable price of only 0.377 $ W<sub>p</sub><sup>–1</sup> (W<sub>p</sub> = peak-Watt), which is appreciably\nlower than that of reported high-performance OSCs. This work offers\na rational guide in the development of low-cost and high-performance\norganic photovoltaic molecules and suggests the great potential of\nPTQ16–10 in cost-effective OSCs for industrialization.