Temperature-induced orbital polarizations and tunable charge dynamics in layered double perovskite thin films

• Main Authors: Arramel, Maddalena, Francesco, Muhammad Haris Mahyuddin, Yin, Xinmao, Tang, Chi Sin, Mohammad Kemal Agusta, Muhammad Fauzi Sahdan, Diao, Caozheng, Dang, Cuong, Muhammad Danang Birowosuto, Wee, Andrew Thye Shen, Rusydi, Andrivo
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2022
• Subjects: Engineering::Electrical and electronic engineering; Double Perovskite; Valence Band
• Online Access: https://hdl.handle.net/10356/162419
• Institution: Nanyang Technological University

The realization of lead-free all-inorganic perovskites in emergent materials requires an in-depth understanding of strongly correlated systems toward optoelectronics or spintronics applications. Herein, we report the electronic and optical variation of the <111>-oriented layered double perovskites (LDP) family with the formula of Cs4MIIBi2Br12 thin films (where MII: Cu, Mn, Pb, or Sr). The element and shell-specific orbital polarization based on soft X-ray linear dichroism spectroscopy probes the Cs M4,5- and Mn L2,3- edges of Cs4MnBi2Br12 thin films as a function of temperature. A strong reversal orbital polarization at the respective edges at 150 K indicates a thermally induced orbital-selective rearrangement at low temperature. In addition, the valence band analysis indicates different orbital admixtures of Br 4p and MII d states, corroborated by the density functional theory calculations. In terms of the transient charge dynamics, we observe the photoluminescence peak maxima position trend line is shifted toward a longer wavelength. In addition, the longest average lifetime is recorded for Cs4CuBi2Br12 at 27.40 ± 1 μs. As the LDP structural integrity is lead-free, therefore, these all-inorganic perovskites hold promising potentials as sustainable and green materials for photophysics applications.