Berlin 2015 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 84: Focus Session (CPP with HL): Hybrid photovoltaics and perovskites II

HL 84.1: Hauptvortrag

Donnerstag, 19. März 2015, 15:00–15:30, C 130

Photophysics of organic-inorganic hybrid lead iodide perovskite single crystals — •Maria Antonietta Loi — Zernike Institute for Advanced Materials, University of Groningen, The Netherlands

Hybrid organometal halide perovskites have been demonstrated to have outstanding performance as semiconductors for solar energy conversion. Further improvement of the efficiency and stability of these devices requires a deeper understanding of their intrinsic photophysical properties. Here we address the intrinsic material physics by investigating the structural and optical properties of high quality single crystals of Methyl Ammonium Lead Iodide from room temperature to 5K. X-ray diffraction reveals an extremely sharp transition at 163 K from a twinned tetragonal I4/mcm phase to a low-temperature phase characterized by complex twinning and possible frozen disorder. Above the transition temperature the photoluminescence is in agreement with a band-edge transition, explaining the outstanding performances of the solar cells. Whereas below the transition temperature, three different features arise, one of which is attributed to a singlet-free-exciton and the other two to bound-triplet excitons. The bound-triplet excitons are characterized by a decay dynamics of about 5μs and by a saturation phenomenon due to many-body interactions. This results in a description of the room temperature recombination as being due to spontaneous band-to-band radiative transitions and weak non-radiative Auger processes, whereas a diffusion-limited behaviour is expected for the low temperature range.