Imaging the Anomalous Charge Distribution Inside CsPbBr₃ Perovskite Quantum Dots Sensitized Solar Cells

Abstract

Highly luminescent CsPbBr perovskite quantum dots (QDs) have gained huge attention in research due to their various applications in optoelectronics, including as a light absorber in photovoltaic solar cells. To improve the performances of such devices, it requires a deeper knowledge on the charge transport dynamics inside the solar cell, which are related to its power-conversion efficiency. Here, we report the successful fabrication of an all-inorganic CsPbBr perovskite QD sensitized solar cell and the imaging of anomalous electrical potential distribution across the layers of the cell under different illuminations using Kelvin probe force microscopy. Carrier generation, separation, and transport capacity inside the cells are dependent on the light illumination. Large differences in surface potential between electron and hole transport layers with unbalanced carrier separation at the junction have been observed under white light (full solar spectrum) illumination. However, under monochromatic light (single wavelength of solar spectrum) illumination, poor charge transport occurred across the junction as a consequence of less difference in surface potential between the active layers. The outcome of this study provides a clear idea on the carrier dynamic processes inside the cells and corresponding surface potential across the layers under the illumination of different wavelengths of light to understand the functioning of the solar cells and ultimately for the improvement of their photovoltaic performances.

Caesium for Perovskite Solar Cells: An Overview

“…Panigrahi et al. claimed that the efficient charge transfer process also depends on the generation and extraction of the charge carriers at the interfaces . The perfect band alignment across the layers of the perovskite absorber, ETL and HTL, facilitated the separation of the photoinduced charge carriers and their transportation to the respective electrodes (Figure A).…”

“… A) Schematic diagram of charge separation in the solar cell under the illumination of the full solar spectrum (white light), together with the scheme of opposite polarities of accumulated charges (electrons and holes) in the two regions (ETL and HTL); B) cross‐sectional SEM image and C) J‐V characteristics and photovoltaic parameters of the solar cell. Adapted and reprinted with permission …”

“…Panigrahi et al claimed that the efficient chargetransfer process also depends on the generation and extraction of the charge carriers at the interfaces. [172] The perfect band alignment across the layers of the perovskite absorber,E TL and HTL, facilitatedt he separation of the photoinduced charge carriers and their transportation to the respective electrodes (Figure 12 A). Kelvin probe force microscopy (KPFM)w as used to investigate the various charge transfer dynamics at the interfaces of the solar cells under different radiation wavelengthso f the full electromagnetic spectrum (white light).…”

“…Lau et al demonstrated al ow-temperature process to synthesise the CsPb 1Àx Sr x I 2 Br compound. [184] The incorporation of [172] strontium (Sr 2 + )i nto CsPbI 2 Br modified both the electronic and the optical properties of the absorber material, as well as the crystallinity and morphology of the resulting perovskite. Figure 13 As hows the XRD patterns of the CsPb 1Àx Sr x I 2 Br films, where the characteristic" snowflakes" morphologyi sc lear in the brighter region of SEM images (Figure 13 B-F).…”

A vertical structure photodetector based on all‐inorganic perovskite quantum dots

“…However, the chemical and thermal instabilities of hybrid perovskites in the presence of light, moisture, and heat remain an obstacle. Compared with the hybrid perovskites, all‐inorganic perovskites, taking the structural form of CsPbX 3 (X = Cl, Br, I), have become exciting materials in research due to their high thermal stability and excellent photoelectric properties, such as large optical absorption, high quantum yields, and long carrier diffusion length and mobility . Herein, we choose all‐inorganic perovskite quantum dots (QDs) to fabricate photodetectors.…”