Multimodal temperature sensing in hybrid perovskites doped with Cr3+: a strategy for optimizing luminescent thermometers

Abstract

Optical thermometry has gained significant attention due, in particular, to its usefulness, with high sensitivity, rapid response, and remote measurement capability. The group of metal–organic frameworks (MOFs) containing Cr³⁺ ions has become a promising material for developing a new branch of optical sensors for low-temperature solutions. Herein, we present possible ways to optimize thermometric properties, with particular emphasis on relative sensitivity (S_r). By comparing different methods of determining the thermometric model, it is possible to observe the impact of individual approaches on the obtained thermometric characteristics. What is more, we report structural and spectroscopic studies of a series of [EA]Mn_1−xCr_x(HCOO)₃, where EA = ethylammonium cation, and x = 0, 0.01, 0.03, and 0.05. Described materials exhibit perovskite-like architectures and a strong dependence of spectroscopic properties on the composition of host materials, dopant concentration, and environmental temperature. XRD analysis provided information on the relationship between chemical composition and structural properties. Investigated samples exhibited spin-forbidden emission and a significantly red-shifted broad emission band. The particular usefulness of hybrid compounds containing Cr³⁺ for luminescence thermometry is confirmed with temperature-dependent (80–300 K) photoluminescence and lifetime measurements. The obtained results show the extraordinary potential of hybrid compounds for luminescence thermometry, depending on the chosen thermometric method (S_r up to 5.14% K⁻¹ at 143 K). So far, this is the highest S_r value ever been reported for a luminescent thermometer based on hybrid organic–inorganic formate perovskite doped with Cr³⁺ ions. In this work, we demonstrate a comparison of different methods of thermometric model determination, based on the ratiometric approach and lifetime analysis. The presented results show the significant importance of thermometric model determination and optimization, which may not only increase the obtained sensitivity of the thermometer but also extend the operation range.