Owing to its indirect band gap, an all-inorganic, lead-free halide double perovskite generally tends to exhibit a low photoluminescence efficiency, thus restricting its applicability as a photovoltaic material. Cs₂AgBiCl₆ is one of the stable halide double perovskites with an indirect band gap of 2.7 eV. Its optoelectronic properties can be enhanced by partially replacing some of the Ag ions with the isovalent Na ions, forming Cs₂Na_xAg_1–xBiCl₆ compositions. The origin of enhanced photoluminescence in these mixed compositions is speculated to be the competitive interaction of both radiative and nonradiative transition, highly influenced by electron–phonon coupling. However, a concrete understanding of the electron–phonon coupling phenomenon and an estimate of its strength is still lacking. Our investigations reveal that the de-excitation process involves decay through trap states formed in the substituted compositions. A quantitative analysis of Raman spectra along with the composition-dependent Urbach tail states and Fano broadening reveals a better understanding of trap state stabilization via strong electron–phonon interaction.

中文翻译：

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揭示影响 Cs2NaxAg1–xBiCl6 混合卤化物双钙钛矿光致发光性质的电子-声子相互作用


由于其间接带隙，全无机、无铅卤化物双钙钛矿通常表现出较低的光致发光效率，从而限制了其作为光伏材料的应用。 Cs ₂ AgBiCl ₆ 是一种稳定的卤化物双钙钛矿，间接带隙为 2.7 eV。通过用等价Na离子部分取代部分Ag离子，形成Cs ₂ Na _x Ag _1–x BiCl ₆