Polarons and Polaritons in Lead Halide Perovskites
Lead halide perovskites have been demonstrated as high performance materials in solar cells and light-emitting devices. These materials are characterized by coherent band transport expected from crystalline semiconductors, but dielectric responses and phonon dynamics typical of liquids. Here I will show that the “crystal-liquid” duality and the soft phonon modes are responsible for large polaron formation and screening of charge carriers, leading to defect tolerance, moderate charge carrier mobility, and low radiative recombination rates (Sci. Adv. 2017, 3, e1701217; Sci. Adv. 2017, 3, e1701469; Nat. Mat. 2018, 17). Large polaron formation, along with the phonon-glass character, explains the dramatic reduction in hot carrier cooling rates (Science, 2016, 353, 1409; JACS 2016, 138, 15717). Besides excellent carrier properties, lead halide perovskite have been demonstrated in high efficiency light emission, including nanowire lasing (Nat. Mat. 2015, 14, 636). I will show that both pulsed and CW lasing in lead halide perovskite nanowires originate from polaritons in the bottleneck region (Adv. Opt. Mat. 2018, 6, 1700982). Time resolved measurement provides a direct view of the kinetic condensation process and reveals intriguing Bose-scattering dynamics in low dimensions.