Regensburg 2016 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 2: Fundamentals of Hybrid and Perovskite Photovoltaics
(Joint symposium of CPP, DF, DS and HL, organized by CPP)

DS 2.3: Hauptvortrag

Montag, 7. März 2016, 10:30–11:00, H1

Charge-Carrier Diffusion and Radiative Efficiencies in Hybrid Metal Halide Perovskites — •Laura Herz — University of Oxford, Oxford, UK

Hybrid metal halide perovskites (stoichiometry AMX₃) have recently emerged as low-cost active materials in PV cells with power conversion efficiencies in excess of 20%. In addition, hybrid perovskites show prospects for applications in low-cost light-emitting diodes and lasers.

Here we discuss how parameters essential for photovoltaic operation, such as charge carrier recombination and diffusion lengths are altered with substitutions of the organic A cation (e.g. methylammonium versus formamidinium), the metal M cation (e.g. Pb²⁺ or Sn²⁺) and the halide X anion (I versus Br). We analyze distinct charge-carrier recombination mechanisms, such as trap-mediated, bi-molecular (electron-hole) and Auger recombination, which show different dependences on composition and temperature.

We use these insights to predict charge-carrier diffusion lengths and radiative efficiencies in the limit of ultra-low trap-related recombination, which could potentially be reached through further advances in material processing. We find that for hybrid lead iodide perovskites with typical charge-carrier mobilities of ∼30cm²/(Vs), charge-carrier diffusion lengths under solar irradiation are unlikely to exceed ∼10µm even if all trap-related recombination is eliminated. We further show that if high radiative efficiencies are to be obtained for intermediate charge-carrier densities (n∼10¹⁴cm⁻³), trap-related recombination lifetimes have to exceed microseconds.