Electromer formation in a diamine derivative under optical excitation: Experimental evidence

The spectral disparity observed under electroluminescence and photoluminescence in organic semiconductors is attributed to the electromer formation. 1,1-Bis((di-4-tolylamino)phenyl)cyclohexane (TAPC), a representative aromatic amine-based organic semiconductor, typically exhibits electromer emission at 580 nm. However, direct evidence clarifying the origin of such electromers has been lacking. In this work, we found that the electromer emission peaking at 580 nm can be generated by the photoluminescence excitation without the presence of electric field, indicating a different perspective of electromer formation in organic semiconductors. We demonstrated that the femtosecond laser treatment induces the formation of electromer species. Through power-dependent and time-resolved photoluminescence analyses, we further investigated the energy transfer between TAPC molecules and the electromer species. Structural characterization reveals that the molecular degradation, resulting from cleavage of one of the two intra-ring carbon–carbon bonds at the carbon atom of the cyclohexane (connecting the two tri-p-tolylamine units), is the origin for electromer emission peaking at 580 nm. This work provides critical insights into electromer origins and advances the rational design of stable organic optoelectronic materials.