Matrix Encapsulation of Solution-Processed Thiophene-Based Fluorophores for Enhanced Red and Green Amplified Spontaneous Emission

Precise control of exciton behavior is key in constructing high-performance material systems for optoelectronic applications. Intrinsic sulfur in building aromatic units always results in strong aggregation, which causes exciton quenching, polaron formation, and enhanced nonradiative components. Herein, a series of solution-processed thiophene-based diarylfluorene derivatives is demonstrated and these fluorophores are encapsulated in the matrix system to suppress polaron formation for efficient green and red amplified spontaneous emission (ASE). A systematic photophysical study in solution, neat films, and polystyrene (PS)-based encapsulated systems reveals that their emission behaviors are substantially promoted in PS encapsulated matrix due to the suppressed intermolecular aggregation. Furthermore, fs-transient absorption (TA) measurements confirm that the encapsulated systems present stimulated emission (SE) and obtain the same intramolecular excited-state character to those in solution, associated with the effective suppression of polaron formation and exciton quenched, in opposition to neat films with broad photoinduced absorption (PA) bands. Therefore, in contrast to the neat spin-coated film without gain processing, these encapsulated systems give rise to notable optical gain properties with threshold values for green and red ASE as low as 70 μJ cm⁻². Molecular encapsulation is an effective strategy to precisely enhance exciton behavior and emission efficiency for optoelectronic applications.