Anti-Stokes photoluminescence of halide perovskite semiconductors for optical refrigerators

The realization of optical refrigeration in semiconductors has been a long-standing challenge for optical science and semiconductor physics, and many studies have been conducted. Recently, halide perovskite semiconductors have been attracting much attention as a possible candidate for optical refrigerators, because of their extremely high photoluminescence (PL) quantum efficiencies. Here we report anti-Stokes PL properties of halide perovskite bulk crystals and quantum wells. Using PL excitation spectroscopy, we determined the lower limit of external quantum efficiency for laser cooling. The strong electron-phonon coupling and unique thermal properties of perovskites are key factors of efficient anti-Stokes PL processes.