Highly efficient and stable binary all-polymer solar cells enabled by sequential deposition processing tuned microstructures

The power conversion efficiency (PCE) and operation stability of all-polymer solar cells (all-PSCs) are expected to be simultaneously pushed to a high level, that can be considered for further commercialization. Here the sequential processing (SqP) method is applied to process the PM6:PY-DT all-polymer system, while the control devices are made from the blend casting (BC) method. As a result, the efficiency rises to 16.5% in SqP devices from 15.8% of their BC counterparts, which is mainly caused by the improved fill factor (FF). Device physics study and morphology analysis reveal that optimized crystallinity and vertical phase separation result in suppressed charge recombination, higher charge collection and transport ability, which is responsible for PV performance improvement. In addition, operational stability is compared by maximal power point (MPP) tracking: the SqP device has a significantly longer time it takes to degrade to 80% of its initial PCE than the BC device, which could be attributed to the vertical composition distribution optimization realized by the two-step coating method. This work successfully demonstrates the effectiveness and promising future of using an SqP method to boost device performance for all-PSCs.