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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 53: Perovskite and photovoltaics II (joint session HL/CPP)

CPP 53.8: Vortrag

Dienstag, 17. März 2020, 15:45–16:00, POT 251

Band Gap Engineering of Double Perovskite Halides Cs₂AgBiCl₆ through Different Sites Alloying — •Dan Han, Masako Ogura, Andreas Held, and Hubert Ebert — Department of chemistry, Ludwig-Maximilians-Universität München, Munich, Germany

Recently, double perovskite halides have been proposed as potential Pb-free photovoltaic materials. However, many experimentally or theoretically reported double perovskite halides have indirect and large band gaps, hindering efficient sunlight absorbing. Thus, tuning the band gap of double perovskite halides is required for their future photovoltaic application. Forming alloys is a practical way for band gap engineering. Here, we presented a systematic study of alloying on different sites for a representative double perovskite halide Cs₂B’B”X₆(B’=Ag, B”=Bi, X=Cl) using the fully relativistic Korringa-Kohn-Rostoker (KKR) Green function in combination with the coherent potential approximation (CPA) method. Cs₂Na_xAg_1−xBiCl₆, Cs₂AgSb_xBi_1−xCl₆ and Cs₂AgBi(Br_xCl_1−x)₆ (x=0.25, 0.5, 0.75) all show a band gap bowing behavior, i.e., a nonlinear band gap dependence on the chemical composition. Additionally, we evaluated the mixing thermodynamical stability of Cs₂AgSb_xBi_1−xCl₆ and show Cs₂AgSb_xBi_1−xCl₆ alloy is thermodynamically stable at room temperature. Bloch spectral functions of alloys with different compositions exhibit broadening due to CPA technique. Alloys at B’ and B” sites could tune the finite lifetime of carrier more effectively than alloys at X site.