Understanding Thermal and A‐Thermal Trapping Processes in Lead Halide Perovskites Towards Effective Radiation Detection Schemes

Abstract

Lead halide perovskites (LHP) are rapidly emerging as efficient, low-cost, solution-processable scintillators for radiation detection. Carrier trapping is arguably the most critical limitation to the scintillation performance. Nonetheless, no clear picture of the trapping and detrapping mechanisms to/ from shallow and deep trap states involved in the scintillation process has been reported to date, as well as on the role of the material dimensionality.Here, this issue is addressed by performing, for the first time, a comprehensive study using radioluminescence and photoluminescence measurements side-by-side to thermally-stimulated luminescence (TSL) and afterglow experiments on CsPbBr 3 with increasing dimensionality, namely nanocubes, nanowires, nanosheets, and bulk crystals. All systems are found to be affected by shallow defects resulting in delayed intragap emission following detrapping via a-thermal tunneling. TSL further reveals the existence of additional temperature-activated detrapping pathways from deeper trap states, whose effect grows with the material dimensionality, becoming the dominant process in bulk crystals. These results highlight that, compared to massive solids where the suppression of both deep and shallow defects is critical, low dimensional nanostructures are more promising active materials for LHP scintillators, provided that their integration in functional devices meets efficient surface engineering.

Ultra-fast low temperature scintillation and X-ray luminescence of CsPbCl3 crystals

“…The delayed component τ 2 with decay time ∼1 ns appears because of formation of bound excitons released from shallow trap states. 28,40 The slow emission component ( τ 3 ), observed below 80 K, is assigned to the radiative recombination of the trapped excitons. This is a thermally activated process and, subsequently, the emission is very slow at low temperature: it mostly contributes to the background at very low temperatures but with increasing temperature this component starts to emerge in the decay curve.…”

Advanced Halide Scintillators: From the Bulk to Nano

“…The most critical issue for scintillator performance can be carrier trapping. The study [ 295 ] shows CsPbBr 3 NCs as superior candidates for scintillating materials compared with higher‐dimensional analogs. CsPbBr 3 with increasing dimensionality, namely, nanocubes, nanowires, nanosheets, and bulk crystals, was comprehensively studied to shed light on trapping and detrapping mechanisms to and from shallow and deep traps.…”

Preparation of ultra-stable and environmentally friendly CsPbBr3@ZrO2/PS composite films for white light-emitting diodes

“…As we all know, perovskite QDs will exhibit different degrees of fluorescence quenching in a thermal environment, which is mainly due to the different trap states appearing inside them. 43,44 Typically, heating-cooling cycle tests are employed to measure the thermal stability of perovskite QDs, whose fluo- rescence intensity decreases with increasing temperature and then gradually recovers as the temperature decreases, exhibiting a reversible fluorescence quenching. However, the fluorescence intensity of perovskite QDs does not return to the initial intensity even when the temperature is lowered to the initial temperature, which is attributed to an irreversible fluorescence quenching.…”