Achieving 19.2% High-Efficiency Ternary Organic Solar Cells Through Novel Sequential Processing Technique With Hydrocarbon Solvent

Abstract

In organic solar cells (OSCs), typical methods for fabricating the ternary active layer are blend-casting (BC) or two-step sequential processing (SqP-2T), where all three or at least two components are blended together, which affect the crystallization/aggregation behavior of each other during solid-film formation. Herein, we introduce for the first time a novel three-step sequential processing method, termed SqP-3T, which utilizes hydrocarbon solvents to prepare high-quality ternary active layers. Compared to the SqP-2T and BC techniques, SqP-3T yields an active layer with a higher acceptor ratio on its upper surface and exhibits a longer crystal coherence length in the out-of-plane direction (21.42 Å). These characteristics enhance charge transport and collection. Additionally, SqP-3T devices demonstrate nearly a twofold increase in the transient photovoltage decay constant (up to 2.82 µs) that is related to carrier lifetime to a certain extent, leading to reduced recombination losses. Consequently, the SqP-3T device achieves a high fill factor (75.67%) and a high short-circuit current density (27.35 mA/cm²), contributing to a power conversion efficiency of 19.2%. These results highlight the potential of SqP-3T or a multi-step sequential deposition process in the production of ternary or multicomponent OSCs, which could be adopted by more material systems in the future.

Keywords

hydrocarbon solvent / ternary devices / three-step sequential processing

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