Selenization Strategy of Phenazine‐based Non‐Fullerene Acceptors Promotes Photon Harvesting and Reduces Voltage Loss in Organic Solar Cells.

Phenazine‐based small molecular acceptors (SMAs), which benefit from the reduced energy loss (<italic>E</italic>loss), have emerged as promising candidates for achieving high‐efficiency organic solar cells (OSCs). Nevertheless, the potential advancements of phenazine‐based photovoltaic devices are hindered by the constrained short‐circuit current (<italic>J</italic>sc). Though the incorporation of selenium (Se) atoms has been proven effective in enhancing <italic>J</italic>sc, it simultaneously introduces molecular disorder stacking and charge recombination. Based on the desire to harness the full potential of phenazine structure and the benefits of Se substitution, a series of Se‐substituted phenazine‐based SMAs, namely PzIC‐SSe‐4F and PzIC‐SeSe‐4F are meticulously synthesized. Due to the increased photon harvesting capabilities, the photovoltaic device using PzIC‐SeSe‐4F demonstrated a significantly increased <italic>J</italic>sc of 27.73 mA cm−2. Remarkably, the PzIC‐SeSe‐4F‐based device displayed an astonishing open circuit voltage (<italic>V</italic>oc) of 0.873 V, representing the highest <italic>V</italic>oc recorded among all reported symmetric Se‐substituted Y‐series SMAs‐based photovoltaic devices. Thanks to the synergistic effect of phenazine central cores and Se substitution, the PM6:PzIC‐SeSe‐4F‐based device achieves a power conversion efficiency (PCE) of 17.69%. The findings serve as a pivotal reference for further development of high‐efficiency Se‐substituted photovoltaic devices. [ABSTRACT FROM AUTHOR]