High‐Efficiency Nano‐Interdigitated Heterojunction Photovoltaics Through Aggregation‐Controlled Film Formation and Nanoimprint Engineering

Optimizing interfacial contact and light management are critical for advancing p/n heterojunction photovoltaic devices. Herein, we demonstrate an interface and optical co-engineering strategy combining controlled D18 incorporation with nanoimprint lithography (NIL) to achieve high-efficiency and durable devices. Introducing 20 wt.% of D18 into the n-type PY-IT layer simultaneously prolongs film-formation kinetics, suppresses excessive PY-IT aggregation from coarse nanoparticles to uniform nanofibrillar networks, and passivates interfacial defects via Lewis acid-base interactions. This yields a planar p (the metal halide is used as p-type layer here with composition of Rb0.03Cs0.05FA0.90MA0.05PbI3)/n (the D18:PI-IT blend is used as n-type layer in this work) device with power conversion efficiency (PCE) of 25.23% (0.09 cm2). Building on this platform, NIL creates a vertically interdigitated p/n architecture that enlarges interfacial area, improves crystallinity, and enhances broadband absorption. The resulting devices deliver a champion PCE of 26.24% (0.09 cm2) and 25.03% (0.5 cm2) with high reproducibility. Critically, unencapsulated devices retain ∼90% efficiency after 1000 h of continuous illumination, demonstrating exceptional operational stability. This work establishes a scalable route toward efficient, durable p/n heterojunction photovoltaics.