Abstract
Halide perovskite solar cells (PSCs) have now developed to achieve conversion efficiencies of more than 26% [1], and the durability time for which PSCs do not suffer a loss in conversion efficiency has reached over 2300 hours [2]. The conversion efficiency of PSCs based on tin (Sn), which is lead-free, has also exceeded 14% and is improving further [3]. It is possible to find the key to improving various physical properties of PSCs by artificially controlling the atomic-level microscopic construction of the crystal structure and interfaces. From this perspective, we have applied laser molecular beam deposition (LMBD), which enables deposition control of organic and inorganic materials at the atomic level, to develop PSCs-related materials [4]. In this study, we investigate the correlation between the laser conditions and the physical properties of the films deposited by continuous infrared (IR) or ultraviolet (UV) pulsed laser deposition of PCSs-related materials.LMBD of PCSs-related materials were conducted using the following process: on a synthetic quartz substrate placed in an ultra-high vacuum chamber a halide perovskite film was formed at room temperature or ~150 ºC by irradiating a semiconductor continuous infrared laser (wavelength: 808 nm) or an Nd:YAG Q-Switch quadruple wavelength UV pulsed laser (wavelength: 266 nm, 10 Hz) onto PbI2 and MAI, or CsPbBr3 material targets. The optical, crystalline, and electrical properties of the films were then characterized by UV-visible spectroscopy, X-ray diffraction (XRD), and I-V measurements, respectively.Figure 1 shows the dependence of deposition rate on laser power density P D for LMBD of CsPbBr3. Interestingly, the deposition rate reaches a maximum at approximately 5 W/cm2 with increasing P D, before decreasing rapidly above this value. This suggests that the effective deposition rate is reduced due to the etching of the deposited surface by the ion bombardment of the laser ablation. Figure 2 illustrates the results of XRD peak intensity normalized by film thickness (red circle) and crystallite diameter (open diamond) estimated from the diffraction peak of CsPbBr3 (220) plotted as a function of P D. This indicates that the orientation of CsPbBr3 (220) becomes more aligned with increasing P D.In this presentation, we will report details of the correlation between LMBD conditions and various properties of PCSs-related materials.
Published Version
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