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.