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

Abstract Phenazine‐based small molecular acceptors (SMAs), which benefit from the reduced energy loss ( E 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 ( J sc ). Though the incorporation of selenium (Se) atoms has been proven effective in enhancing J 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 J sc of 27.73 mA cm −2 . Remarkably, the PzIC‐SeSe‐4F‐based device displayed an astonishing open circuit voltage ( V oc ) of 0.873 V, representing the highest V 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.