The Theoretical Comparison of Different Content of the Third Component in Ternary Organic Solar Cells

Abstract

The ternary strategy has been rapidly developed in organic solar cells (OSCs), however, due to the complexity of the active layer stacking pattern and the ternary charge transfer (CT) mechanism, the selection and content of the third component are still elusive. In this work, two ternary active layers B1:Y7 (10wt%):BO-4Cl and B1:Y7 (50wt%):BO-4Cl are constructed to reveal the effect of stacking pattern on power conversion efficiency (PCE). Their intrinsic properties are investigated using two independent binary cells (B1:BO-4Cl (D/A1) and B1:Y7 (D/A2)). The corresponding charge transfer mechanisms of each binary complex were analyzed and different stacking pattern of these complexes (IC-T, IC-RHD, IC-BEDT) were classified. Also, the numbers of net charge transfer and the number of CT state for trimers are explored. The results show that the binary complexes in B1:Y7 (10wt%):BO-4Cl-cell has more CT states and CT mechanisms. Besides, more IC-T stacking patterns in 10wt% complexes were found. The stacking of IC-T has greater electronic separation coupling, smaller electronic recombination coupling, more favorable rate of charge separation and recombination, and more stable interaction energy, which is more conducive to the charge separation and effectively inhibit the charge recombination, explaining the reason why B1:Y7 (10wt%):BO-4Cl has a higher PCE than B1:Y7 (50wt%):BO-4Cl. For trimer, more CT paths exist at B1:Y7 (10wt%):BO-4Cl-cell, which promotes the CT efficiency and improves the PCE. In addition, this work provides basic knowledge for the influence of the third component content on the performance of ternary organic solar cells, providing theoretical guidance for the experimental work of Y-series NFAs material.

Keywords: ternary organic solar cells, Y-series Non-fullerene acceptor, charge transfer mechanism, the stacking pattern