Constructing high efficiency non-fullerene all-small-molecule ternary organic solar cells by employing structurally similar acceptors

Significant progress has been made in organic solar cells over the past few years. However, the power conversion efficiency of all-small-molecule systems is still lower than that of polymer photovoltaics. Ternary strategies lead to a potential way to improve the performance of all-small-molecule organic solar systems. In this article, an all-small-molecule ternary organic solar cell is presented by incorporating a small amount of the IDIC acceptor into a ZR1-Cl : IDIC-4Cl based binary system. On the basis of the enhanced absorption spectrum, the good miscibility enabled by two structurally similar acceptors can potentially form receptor alloys, leading to a simultaneous increase in both short circuit current density and open circuit voltage to 18.64 mA cm−2 and 0.90 V, respectively. Characterizations such as transmission electron microscopy and grazing-incidence wide-angle scattering confirmed good miscibility, ordered packing and high crystallinity in the ternary film with a fibrous structure that benefits electron transfer, increasing the fill factor to 69.66%. The simultaneous increment in short circuit current, open circuit voltage and fill factor increases the power conversion efficiency from 10.81% in the binary system to 11.65% in the ternary system.