Structure, Luminescence and Temperature Detection Capability of [C(NH 2 ) 3 ]M(HCOO) 3 (M = Mg 2+ , Mn 2+ , Zn 2+ ) Hybrid Organic-Inorganic Formate Perovskites Containing Cr 3+ 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 2 ) 3 ]M(HCOO) 3 (Mg 2+ , Mn 2+ , Zn 2+ ) doped with Cr 3+ ions. Crystal field strength (Dq/B) and Racah parameters were determined based on diffuse reflectance spectra. It was shown that Cr 3+ 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 3+ ions enable the proposal of an approach for remote readout of the temperature. The relative sensitivity (S r ) can be easily modified by sample composition and Cr 3+ ions concentration. The luminescent thermometer based on the 2 E/ 4 T 2g transitions has the relative sensitivity S r of 2.08%K -1 at 90 K for [C(NH 2 ) 3 ]Mg(HCOO) 3 : 1% Cr 3+ and decrease to 1.20%K -1 at 100 K and 1.08%K -1 at 90 K for Mn 2+ and Zn 2+ analogs, respectively.