Kinetically Controlled Direct In Situ Photolithography of Perovskite Color‐Conversion Layers

ABSTRACT Metal halide perovskites (MHPs) are promising materials for color‐conversion layers (CCLs) owing to their high absorption coefficients and narrow emission bandwidths. However, high‐resolution patterning of micrometer‐thick MHP CCLs remains challenging due to their susceptibility to optical and chemical damage during conventional patterning processes. Direct in situ photolithography has emerged as a potential solution by enabling high‐thickness pattern formation without directly exposing MHP emitters to harsh conditions, yet its achievable spatial resolution has remained limited. Here, we report a kinetically controlled direct in situ photolithography (KC‐ISP) approach for high‐resolution MHP CCLs. By controlling thiol–ene crosslinking kinetics and incorporating a precursor‐redistributing spin‐washing step, KC‐ISP enables high‐resolution patterning with feature sizes down to ∼3 µm while providing facile color tunability through controlled precursor composition. In addition, in situ crystallized MHPs exhibit a pronounced increase in photoluminescence quantum yield upon air exposure, attributed to phase redistribution and surface defect passivation under ambient conditions. As a result, our MHP CCLs with ∼4 µm thickness achieve blue uptake values of ∼80% and ∼98% for green and red emitters, respectively, with corresponding color‐conversion efficiencies of ∼45% and ∼30%, demonstrating the potential of KC‐ISP for high‐resolution micro‐display applications.