Design of Near‐Infrared Nonfullerene Acceptor with Ultralow Nonradiative Voltage Loss for High‐Performance Semitransparent Ternary Organic Solar Cells

Abstract Semitransparent organic solar cells (ST‐OSCs) are considered as one of the most valuable applications of OSCs and a strong contender in the market. However, the optical band gap of current high‐performance ST‐OSCs is still not low enough to achieve the optimal balance between power conversion efficiency (PCE) and average visible transmittance (AVT). An N ‐substituted asymmetric nonfullerene acceptor SN with over 40 nm bathochromically shifted absorption compared to Y6 was designed and synthesized, based on which the device with PM6 as donor obtained a PCE of 14.3 %, accompanied with a nonradiative voltage loss as low as 0.15 eV. Meanwhile, ternary devices with the addition of SN into PM6 : Y6 can achieve a PCE of 17.5 % with an unchanged open‐circuit voltage and improved short‐circuit current. Benefiting from extended NIR absorption and lowered voltage loss, ST‐OSCs based on PM6 : SN : Y6 were fabricated and the optimized device demonstrated a PCE of 14.0 % at an AVT of 20.2 %, which is the highest PCE at an AVT over 20 %.