Manipulating Conical Intersections via a Noncovalent Strategy for Enhanced Photothermal Conversion

Abstract

ABSTRACT Organic photothermal materials (OPMs) utilize efficient nonradiative decay for photothermal conversion, with conical intersections (CIs) playing a crucial role in dissipating excited‐state energy. Current strategies for manipulating CIs remain largely confined to covalently bonded systems, leaving noncovalent approaches largely unexplored. Herein, we propose a cocrystal‐based noncovalent strategy to modulate CI‐mediated nonradiative decay. Specifically, phenoxazine (PXZ) or phenothiazine (PTZ) were paired with 1,2,4,5‐tetracyanobenzene (TCNB) to construct robust donor–acceptor (D‐A) cocrystals. Crystal structure analysis reveals that cocrystal formation transforms the molecular packing from a herringbone to a parallel arrangement, thereby enabling intermolecular motions. Theoretical calculations uncover a favorable relaxation pathway from the Franck–Condon (FC) region to the CI in PXZ‐TCNB, with a relaxation energy Δ E = −16.92 kcal mol −1 . Femtosecond transient absorption (Fs‐TA) spectroscopy confirms a rapid 11.16 ps relaxation process, demonstrating effective CI‐mediated nonradiative decay. Consequently, both PXZ‐TCNB and PTZ‐TCNB exhibit significantly enhanced photothermal performance compared with their individual components. Leveraging its excellent photothermal conversion efficiency (PCE), we successfully integrated this material into a thermoelectric generator (TEG) for light‐driven power generation and fabricated flexible photothermal films with light‐responsive actuation. This work establishes noncovalent engineering as a promising strategy for regulating CI processes and advancing high‐performance OPMs.