Thermal properties of CsPbCl₃ thin films across phase transitions

Abstract

The local thermal conductivity, thermal diffusivity, and volumetric heat capacity of cesium lead chloride perovskite thin films are mapped simultaneously and with highest spatial resolution by a scanning near-field thermal microscope. Both, the 3D phase (CsPbCl 3 ) and the 0D phase (Cs 4 PbCl 6 ) are investigated. For CsPbCl 3 thin films the variation of the thermal properties across the phase transitions in the range from room-temperature to 65°C are analyzed. While the thermal conductivity at room temperature is ultra-low, a significant increase of the thermal conductivity is found for the cubic phase of CsPbCl 3 (T>46°C). While only slight variations in the thermal conductivity are detectable for transitions from the monoclinic to the orthorhombic to the tetragonal phase, thermal diffusivity and volumetric heat capacity measurements are extremely sensitive to the amount of heat involved in the respective transition. It is shown that upon transition to the cubic phase of CsPbCl 3 thin films, the relative increase of the volumetric heat capacity is significantly higher than that of the thermal conductivity. Thus, the thermal diffusivity in the cubic phase becomes notably lower in comparison to that of the respective phase at room temperature. An increase of the volumetric heat capacity had been theoretically predicted earlier but could not be confirmed in previous experimental studies. The findings of our thermal analysis are of great general importance for fundamental material research and for the thermal design of thin-film devices based on CsPbCl 3 perovskites.

Thermal properties of metal-halide perovskites

“…49 These thermal conductivities are somewhat lower than those recently found for CsPbCl 3 thin films with large laterally extended crystallites (0.49 W (m K) À1 ). 51 Note that, since the phonon mean-free-path is also reduced by defects, thermal conductivities are lower near grain boundaries in thin films, as shown in local thermal conductivity analyses with a high spatial resolution by an AFM based technique. 50 This technique allows determining the local thermal diffusivity, aside from the local thermal conductivity; thus the local volumetric heat capacity can be calculated afterwards.…”

“…( r) of 1.3 J cm À3 K À1 and 0.9 J cm À3 K À1 were determined for CsPbBr 3 and CsPbCl 3 at RT respectively. 50,51 The findings of these studies suggested that heat dissipation in dynamically operated halide perovskite optoelectronic devices will be very inefficient. As such, the thermal management of light-emitting diodes and lasers based on halide perovskites is a challenge and requires particular attention (see strategies to enhance the thermal properties of transport layers in perovskite devices).…”

Halide Perovskites: Thermal Transport and Prospects for Thermoelectricity

“…Compared to 3D perovskites, lower κ is observed in the case of 0D perovskites such as (MA) 3 Bi 2 I 9 and Cs 4 PbCl 6 . [ 93,94,119 ] Discrete octahedra structure with low group velocities, reduced phonon lifetimes, and the localization of vibrational energy leads to the ultralow κ in 0D perovskites. [ 64,93 ]…”

Low‐Dimensional‐Networked Cesium Lead Halide Perovskites: Properties, Fabrication, and Applications

“…As a frequently used method in the fabrication of perovskite films, chemical vapor deposition (Figure 15a) was also employed in the synthesis of the dual-phase inorganic CsPbX 3 / Cs 4 PbX 6 perovskite film. [172][173][174][175][176][177] During the preparation process, it was found that the CsBr/PbBr 2 ratio was a very significant parameter in determining the PL emission intensity. [172] When the ratio was 44:16.5, the sample exhibited the highest PL efficiency (Figure 15b,d,e).…”