Energetic Disorder and Activation Energy in Efficient Ternary Organic Solar Cells with Nonfullerene Acceptor Eh-IDTBR as the Third Component

Solution-processed ternary organic solar cells (OSCs) contain a third component in the active layer in addition to the donor/acceptor materials. Two main avenues are considered to fabricate ternary OSCs: 1) to improve the short-circuit current density by the selected third component that broadens and/or enhances the absorption of the host films and 2) to increase the fill factor by adding materials with diverse crystallinity to tune the film morphology. However, little work is reported for the improvement of open-circuit voltage (V-OC), energetic disorder, charge transfer state energy (E-CT), and activation energy in ternary OSCs. Herein, ternary OSCs with active layer composed of PCE10:F8IC:Eh-IDTBR as the model to examine these parameters in addition to the morphology are used. In the ternary device, the additional Eh-IDTBR improves the crystallinity of the acceptor phase in the ternary mixture; the V-OC is 58 mV higher than that of the reference caused by the reduced energetic disorder; due to the good miscibility of Eh-IDTBR with both PCE10 and F8IC, only 50 meV in E-CT is observed; and the zero-field activation energy is lower than that for the reference. The findings provide an alternative way to understand the complex ternary OSC structural-electrical properties' correlations.