Organic solar cells with 20.82% efficiency and high tolerance of active layer thickness through crystallization sequence manipulation.

Printing of large-area solar panels necessitates advanced organic solar cells with thick active layers. However, increasing the active layer thickness typically leads to a marked drop in the power conversion efficiency. Here we developed an organic semiconductor regulator, called AT-β2O, to tune the crystallization sequence of the components in active layers. When adding AT-β2O in the donor (D18-Cl) and acceptor (N3) blend, N3 crystallizes behind D18-Cl, and this phenomenon is different from the co-crystallization observed in binary D18-Cl:N3 blends. This manipulation of crystallization dynamics is favourable to form bulk-heterojunction-gradient vertical phase separation in the active layer accompanied by the high crystallinity of the acceptor and balanced charge carrier mobilities in thick films. The resultant single-junction organic solar cells exhibited a certified power conversion efficiency of over 20%, as well as demonstrated exceptional adaptability across the active layer thicknesses (100-400 nm) and remarkable universality. Such breakthroughs enable large-area modules with a certified power conversion efficiency of 18.04%.