Abstract
The kinetic of low-temperature carrier and lattice of lead-halide perovskite is yet to be fully understood.In this work,we investigate the steady-state photoluminescences(PLs)of CsPbI3 at the environmental temperature(Te)ranging from 20 K to 300 K,and observed anomalous behaviors at cryogenic tempera-tures:The carrier temperature(Tc)of pure CsPbI3 exhibits a negative correlation with Te,accompanied by an expansion in Urbach tails of absorption spectra(Abs.)and excessive red-shifts at peak energy of PLs.These phenomena are also observed in those samples containing a certain amount of Cs4PbI6,but to a lesser extent and occurs at lower temperatures.It is attributed to the intensified hot phonon bottleneck effect(HPB)in CsPbI3 at cryogenic Te,which hinders the energy transfer from hot carriers,via longi-tudinal optics(LO)phonons to longitudinal acoustic(LA)phonons,to the ambient.For samples under continuous-wave laser excitation,in specific,the barrier induced by the enhanced HPB at low Te pre-vents the effective thermalization among carriers,LO and LA phonons,which,therefore,form thermally isolated ensembles with different temperatures.At cryogenic Te range,the elevated temperatures of car-rier and LO phonon expand the high-energy side of PLs and the low-energy tail of Abs.,respectively.For those samples in which the CsPbI3 is mixed with Cs4PbI6,the interfacial LO-LO interaction across them provides a bypass for heat dissipation,mitigating the heat accumulation in LO-phonons of CsPbI3.The results suggest that a strong HPB effect may break the thermal equilibrium among different branches of phonons in the lattice under certain extreme conditions.
基金项目
National Natural Science Foundation of China(62374142)
National Natural Science Foundation of China(12175189)
National Natural Science Foundation of China(11904302)
External Cooperation Program of Fujian(2022I0004)
Fundamental Research Funds for the Central Universities(20720190005)
Fundamental Research Funds for the Central Universities(20720220085)
Major Science and Technology Project of Xiamen in China(3502Z20191015)
万方数据