Nonfullerene Acceptors with Aromatic Heterocycle Substitutions for Efficient Organic Solar Cells

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Modifying the end groups of nonfullerene acceptors presents a viable strategy for enhancing the efficiency of organic solar cells (OSCs). This study synthesized three nonfullerene acceptors─BO-ICTz, BO-ICTzTh, and BO-ICTh─by incorporating aromatic heterocycle substitutions into the end group. These substitutions included an electron-donating thiophene ring, an electron-withdrawing thiazole ring, and a combination of both asymmetric rings. BO-ICTh, exhibiting a stronger conjugation effect, exhibited robust and broad absorption spectra, along with elevated energy levels. When blended with the polymer donor JD40-BDD20, the optimized BO-ICTh-based device achieved a champion power conversion efficiency (PCE) of 16.25%, surpassing devices based on BO-ICTz and BO-ICTzTh. Further analysis of energy loss, charge generation, recombination, and morphology demonstrated that incorporating the aromatic heterocycle ring into the end group presents as a promising strategy for developing nonfullerene acceptors, thereby enhancing the performance of organic photovoltaic devices.