Improving current and mitigating energy loss in ternary organic photovoltaics enabled by two well-compatible small molecule acceptors

Ternary organic photovoltaic (OPV) strategy is an effective but facile approach to enhance the photovoltaic performance for single-junction devices. Herein, a series of ternary OPVs were fabricated by employing a wide bandgap donor (PBDB-TF) and two acceptor-donor-acceptor (A-D-A)-type nonfullerene small molecule acceptors (NF-SMAs, called F-2Cl and 3TT-OCIC). As the third component, the near-infrared SMA, 3TT-OCIC, has complementary absorption spectrum, narrow bandgap and well-compatible crystallization property to the host acceptor (F-2Cl) for efficient ternary OPVs. With these, the optimal ternary devices yield significantly enhanced power conversion efficiency of 15.23%, one of the very few examples with PCE higher than 15% other than Y6 systems. This is mainly attributed to the increased short-circuit current density of 24.92 mA cm −2 and dramatically decreased energy loss of 0.53 eV. This work presents a successful example for simultaneously improving current, minimizing energy loss and together with modifying the morphology of active layers in OPVs, which will contribute to the further construction of high performance ternary OPVs.