Structure, Luminescence and Temperature Detection Capability of [C(NH)]M(HCOO) (M = Mg, Mn, Zn) Hybrid Organic-Inorganic Formate Perovskites Containing Cr Ions.

Metal-organic frameworks are of great interest to scientists from various fields. This group also includes organic-inorganic hybrids with a perovskite structure. Recently their structural, phonon, and luminescent properties have been paid much attention. However, a new way of characterization of these materials has become luminescence thermometry. Herein, we report the structure, luminescence, and temperature detection ability of formate organic-inorganic perovskite [C(NH)]M(HCOO) (Mg, Mn, Zn) doped with Cr ions. Crystal field strength (Dq/B) and Racah parameters were determined based on diffuse reflectance spectra. It was shown that Cr ions are positioned in the intermediate crystal field or close to it with a Dq/B range of 2.29-2.41. The co-existence of the spin-forbidden and spin-allowed transitions of Cr ions enable the proposal of an approach for remote readout of the temperature. The relative sensitivity (S) can be easily modified by sample composition and Cr ions concentration. The luminescent thermometer based on the E/T transitions has the relative sensitivity S of 2.08%K at 90 K for [C(NH)]Mg(HCOO): 1% Cr and decrease to 1.20%K at 100 K and 1.08%K at 90 K for Mn and Zn analogs, respectively.