Controlled Branching of Organic Microcrystals: Branching Rules, Effective Screening, and Advanced Photonic Functions

Hierarchically branched microcrystals from π-conjugated compounds represent prominent advances toward intricate microstructures yet systematic studies on branching remain lacking, hindering the elucidation of general rules and structural control. Herein, we address this gap by establishing a generalizable strategy for controlled branching in cavity-adaptive cocrystals assembled from a distyrylbenzene host and three guests. Simply modulating supersaturation during co-assembly drives morphological evolution from straight microribbons to crossed and hierarchical branched architectures. Combined structural and kinetic analyses reveal the underlying branching rules/mechanism, which are further validated across different material systems. This approach transforms branching control from empirical trial-and-error into a predictable process, enabling effective screening of diverse branched libraries. Notably, despite intricate morphologies, the branched microcrystals retain amplified spontaneous emission performance comparable to their unbranched counterparts. Our findings provide mechanistic insights into branching formation and offer a rational pathway toward predictive design of functional organic branched microcrystals.