A low-cost wide bandgap polymer based on carboxylate substituted thiazole enables efficient organic solar cells with remarkable batch-to-batch reproducibility

Abstract

Constructing the low-cost, high-efficiency, and good batch-to-batch reproducibility polymer donor is vitally important for the application of organic solar cells. Herein, we develop a structurally simple carboxylate-substituted thiazole as an electron-withdrawing building block to construct a low-cost polymer, PBTTzE, containing a facilely prepared chlorinated benzo[1,2-b:4,5-b′]dithiophene (BDTCl) donor unit. Benefiting from synergistic electron deficient effects of chlorination and ester group and C=N, as well as the noncovalent interaction of S⋯O and S⋯N, PBTTzE exhibits a deep HOMO energy level (−5.59 eV), and a planar skeleton structure. When combined with the IT-4F acceptor, the polymer (54 kDa) demonstrated a champion PCE of 15.87%, which is the highest value in the IT-4F-based binary devices to date. Moreover, PBTTzE exhibits excellent batch-to-batch reproducibility due to its very similar PCEs within a range of 43–76 kDa. In addition, an alloyed state and complementary absorption can be formed between PM6 and PBTTzE. Therefore, in a ternary device with PBTTzE added to the PM6:BTP-eC9 blend, a top PCE of 18.76% is achieved due to the suppressed energy loss, prolonged exciton diffusion distance, and improved charge transport. Our work demonstrates that the carboxylate-substituted thiazole is a highly promising acceptor unit for constructing low-cost and high-performance polymers.