Fine-tuning the hierarchical morphology of multi-component organic photovoltaics via a dual-additive strategy for 20.5% efficiency

The multiple-component strategy shows great potential in optimizing the performance of organic photovoltaics (OPVs), while the addition of extra components does not usually guarantee a positive effect on the already-perfected morphology of the binary blend, and thus results in an inferior device performance. To address this issue, we develop a facile dual-additive strategy to compensate the negative effect caused by extra components, and this allows the full exploitation of the multiple-component strategy toward a breakthrough in device performance. Specifically, by employing the dual additives of liquid additive 1,8-diiodooctane and solid additive 1,4-diiodobenzene, the film formation kinetics are optimized, and an optimal hierarchical morphology is formed with balanced crystallization, phase separation and prominent vertical distribution. Therefore, this dual-additive strategy leads to efficient exciton dissociation, charge transport, reduced exciton recombination and suppressed energy loss, offering great promise for high performance OPVs. Consequently, we reach a high efficiency of 20.52% (certified 19.92%) in single-junction OPVs. This work highlights the importance of morphology control for multi-component OPVs and sets a benchmark to accelerate their commercialization.