Yb/Er: Cs2Ag(In/Bi)Cl6 lead-free double perovskite for dual-modal optical temperature sensing

Exploring new optical thermometric materials is important to realize highly accurate temperature detecting. Herein, Yb/Er activators are successfully doped into Cs2Ag(In/Bi)Cl6 lead-free double perovskite (DP) semiconductor, providing dual-modal photoluminescence originated from self-trapped exciton recombination and 4f-4f transitions of Yb/Er dopants as well as Er3+ upconversion emissions. Remarkably different temperature-dependent emissive behaviors from DP host and Yb/Er activators are experimentally demonstrated, which enables to design novel fluorescence intensity ratio (FIR) between DP and Yb/Er based thermometric technology. In addition, upconversion FIR-based temperature sensing via thermal population between the 2H11/2 level and 4S3/2 one of Er3+ dopants in DP host is also realized. It is believed that the present Yb/Er: Cs2Ag(In/Bi)Cl6 DP with excellent long-term stability and dual-functional temperature detecting is a suitable candidate as the self-calibrated optical thermometric material.