Nanoimprint Lithography‐Dependent Vertical Composition Gradient in Pseudo‐Planar Heterojunction Organic Solar Cells Combined with Sequential Deposition

Abstract Although suitable vertical phase separation morphology in organic solar cells (OSCs) can be obtained by the donor/acceptor sequential deposition (SD) method, the lack of precisely adjusting vertical composition gradient and molecular crystallinity is a key limitation. Here, nanoimprint lithography (NIL) combined with SD dual‐functionalized regulation strategy is first used to fabricate high‐performance pseudo‐planar heterojunction (PPHJ) OSCs, which is conducive to constructing vertical bi‐continuous donor/acceptor network to provide sufficient charge separation interface area and orderly charge transport channels. PM6 donor with regular periodic nanograting structure and improved crystallinity is formed via NIL, effectively avoiding the erosion problem ascribed from the subsequent depositing of the Y6 acceptor. Furthermore, the finite‐different time‐domain (FDTD) measurement is employed to confirm the vertical composition gradient of the donor/acceptor, revealing a strong regular light absorption and reduced voltage loss. As a result, the best‐imprinted device enables a power conversion efficiency as high as 17.36%, which is higher than the control SD‐based device (15.46%). It is the first time to obtain high‐quality PM6 nanograting by NIL, which can provide an avenue to form favorable phase separation morphology and adjust the vertical composition gradient for the high‐performance PPHJ OSCs.