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

ABSTRACT 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 Rb _0.03 Cs _0.05 FA _0.90 MA _0.05 PbI ₃ )/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 cm ² ). 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 cm ² ) and 25.03% (0.5 cm ² ) 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.