Collaborative Optimization of Charge Carrier Dynamics and Energy Loss of Organic Solar Cells via Rational Morphology Regulation

Abstract

Generally, the required dominant J-aggregation and ordered molecular stacking via morphology optimization gives rise to red-shifted absorption spectrum with lower optical energy bandgap (E_g), resulting in the adverse effect on the open-circuit voltage (V_oc) improvement in organic solar cells (OSCs). To maximize power-conversion efficiency (PCE), it is desirable to reduce the energy loss (E_loss) of OSCs to refrain from decreasing the V_oc via rational morphology optimization. Herein, we reveal the effect of solid additive treatment on collaboratively optimizing the charge carrier dynamics and E_loss to maximize short-circuit current density and fill factor without decreasing the V_oc of OSCs. In addition to improving the J-aggregation and molecular stacking of D18:N3 blend for efficient charge separation and transport, it is found that the biphenyl (BPh) additive treatment significantly reduces the E_loss to offset the lower E_g for maintaining the high V_oc of OSCs. As a result, the BPh additive treatment shows remarkable effect in boosting the PCE of OSCs. In particular, the BPh additive treatment for the D18:N3:L8-BO-4Cl-based device significantly elevates the PCE from 18.95% to 20.10%.

Keywords

aggregation / charge-transfer state / organic solar cells / power conversion efficiency / solid additive

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