Abstract:Our recentstudy on charge generation and recombination in bulk-heterojunction and planar-mixed heterojunction blends comprising a crystalline polymer donor with Se-containing Y6-derived non-fullerene acceptors has shown both high photovoltaic internal quantum efficiencies and high external electroluminescence quantum efficiencies.Crystallographic and spectroscopic studies reveal that the pseudo-2D, fused-ring molecular acceptors are not only intrinsically highly luminescent but also meets the criteria in achieving intrinsically radiative recombination within the blend by promoting delocalized excitons with much longer luminescent lifetime and reduced exciton binding energies.

These results provide the important demonstration of efficient OPV blends to achieve PCEs over 20%. Regarding the development of perovskite solar cells (PSCs),several novel interface and additive engineering approaches have been employed to enable PSCs to show very highPCE (26.7%) and stability in the inverted architecture devices. Moreover, new multifunctional redox mediators have also been developed to overcome the halide segregation issues that strongly hinder the development of highly efficient and stable large-bandgap PSCs. The resulting devices showed very low photovoltage loss and high PCE >20%. Their integration with OPV to form 2-T tandem devices has shown record-high PCE of 26.2% with good operational stability.