Fig. 1: The conversion of Cu+ to Cu2+ induces the Jahn-Teller effect upon photoexcitation of Cs3Cu2I5.
From: Spin-polarized self-trapped excitons in low-dimensional cesium copper halide
a In conventional DMS QD, the overlapping of Wannier exciton wavefunction with that of magnetic dopant is small while for b STE (a unique Frenkel exciton), this overlapping is large. c The structural transition from [Cu2I5]3− (left) to [Cu2I5]2− (right) upon UV light excitation. The dumbbells represent the atomic orbital on the Cu and I sites; upon excitation, the I:5pz orbital and Cu:3dxy orbital overlap (blue dumbbells) and drive the J-T distortion. d Schematic diagram of energy levels for ground and excited states of Cs3Cu2I5 in tetrahedral crystal fields before and after UV excitation. e ESR spectra of Cs3Cu2I5 without (dark) and with UV-light illumination (Light, T = 300 K, 200 K, 120 K, 77 K), the gray curves show the simulation results considering a tetragonal J-T distortion.
