Enhancing photon recycling of perovskite nanosheet by two-photon excitation

Nanometer scale light penetration depths of halide perovskite (HP) set an intrinsic limit on the performance improvement of optoelectronic devices. Here, we show that two-photon excitation can overcome this limit by markedly increasing the light penetration depth and significantly enhance photon recycling. Through a comparison study between one-photon and two-photon excitations by femtosecond laser pulses in a CsPbBr3 nanosheet, our results demonstrate that two-photon excitation can increase photocarrier transport distance by about 900 nm, which is even comparable to the photocarrier diffusion length. Our work provides substantial insights into the photon recycling of HP induced by nonlinear optical excitations, which can benefit the performance optimization of advanced optoelectronic devices.