Enhancement of Photocarrier Lifetimes in Infrared-Laser-Deposited CsPbBr₃ Films Using a CsBr Underlayer

Thisstudy used photocarrier lifetime measurements to demonstratethat the insertion of a CsBr underlayer enhances the quality of CsPbBr3 films grown via infrared (IR) laser deposition. Thermal desorptionspectrometry indicated that the CsPbBr3 crystal tendedto be Cs-deficient under vacuum. In fact, direct growth of a CsPbBr3 film on an & alpha;-Al2O3(0001) substrateresulted in contamination by an impurity phase of CsPb2Br5, thereby degrading the optical characteristics ofthe CsPbBr3 films. To mitigate CsPb2Br5 contamination, a two-step film preparation process was employedto obtain the growth window for the IR-laser deposition of the CsPbBr3 thin films. First, a CsBr underlayer was deposited at roomtemperature. CsPbBr3 thin films were subsequently depositedonto the underlayer at 150 & DEG;C. Consequently, the CsBr underlayerwas found to suppress the precipitation of the impurity phase andimprove the functional properties of the CsPbBr3 films.Furthermore, photocarrier lifetime measurements were performed toassess the quality of the CsPbBr3 thin films. Notably,time-resolved microwave conductivity measurements revealed that theCsBr underlayer not only doubled the photocarrier lifetime but alsotripled the photoconductivity. Thus, the use of a thin underlayeris expected to be an essential synthesis parameter for fine-tuningthe growth window and improving the physical properties of halideperovskite films.