Defects, (Sb, Er) Dopant Interactions, and Band Gap Engineering in Cs2AgInCl6 Double Perovskites
Inna A. Ivashchenko, Wojciech Piotrowski, Marcin Nyk, Lubomir D. Gulay, Volodymyr O. Yukhymchuk, Galina Gurieva, Andreas Eich, Susan Schorr, Beata Szreniawa, Oleg Yu. Khyzhun, Natalya Kurgan, Malgorzata Makowska-Janusik, Karina V. Lamonova, Katarzyna Matras-PostołekAbstract
In this work, the double perovskite Cs2AgInCl6 and its Sb3+- and Er3+-doped powders have been studied to understand how defects and dopants influence optical characteristics. Incomplete AgCl incorporation creates Vk and F centers, as well as defect-related In+ and Ag– states, leading to photoluminescence (PL) bands at approximately 440, 610, and 630 nm, with the dominant peak at 630 nm. Cs2AgInCl6 exhibits a direct band gap of 4.29 eV, which is reduced by chlorine vacancies. Sb3+ doping results in weak PL, whereas Er3+ introduces visible-near-infrared (Vis-NIR) emission (525–1520 nm). Density functional theory (DFT) supports these observations, predicting a direct 4.42 eV gap for Cs2AgInCl6, narrowed by chlorine cation defects (3.3–3.9 eV), Sb3+ (3.41 eV), and Er3+ (3.97 eV) incorporation. Overall, the findings suggest that emission efficiency is limited by complex defect-dopant interactions; however, band gap tuning through doping indicates potential applications for wide-range photodetection.