Reversible Triple-Mode Photo- and Radioluminescence and Nonlinear Optical Switching in Highly Efficient 0D Hybrid Cuprous Halides

Multifunctional stimuli-responsive luminescent and optical switching is extremely crucial for wide advanced photonic applications, but it remains a challenging objective for halide perovskites. Herein, by performing single-crystal to single-crystal (SC–SC) transformation as a dynamic molecular strategy, we realized a reversible triple-mode photoluminescence, radioluminescence (PL and RL), and nonlinear optical (NLO) switching in a pair of zero-dimensional (0D) hybrid cuprous halides of [ETPP]2Cu4Br6 and [ETPP]CuBr2. Specifically, [ETPP]2Cu4Br6 and [ETPP]CuBr2 display highly efficient yellow and green light emissions under UV light excitation with the highest quantum yield of up to near unity. Simultaneously, identical radioluminescence can also be activated by using X-ray as RL with a light yield of up to 57,974 photons MeV–1, surpassing most of the previously reported hybrid cuprous halides. Most remarkably, reversible SC–SC transformation between them can be realized in an ethanol impregnation-heating process, which provides reversible PL/RL transitions in two light-emitting states. Additionally, this process is also accompanied by transition between the centrosymmetric NLO-inactive [ETPP]2Cu4Br6 and noncentrosymmetric NLO-active [ETPP]CuBr2 through reversible second harmonic generation (SHG) "silent-active" switching. To the best of our knowledge, this is the first reported triple-mode reversible PL, RL, and SHG switching in halide perovskite chemistry, which can realize advanced applications in data storage, information security, optical logic gates, etc.