Electron Transport Layer Engineering Induced Carrier Dynamics Optimization for Efficient Cd‐Free Sb₂Se₃ Thin‐Film Solar Cells

Abstract

Antimony selenide (Sb2Se3) is a highly promising photovoltaic material thanks to its outstanding optoelectronic properties, as well as its cost‐effective and eco‐friendly merits. However, toxic CdS is widely used as an electron transport layer (ETL) in efficient Sb2Se3 solar cells, which largely limit their development toward market commercialization. Herein, an effective green Cd‐free ETL of SnOx is introduced and deposited by atomic layer deposition method. Additionally, an important post‐annealing treatment is designed to further optimize the functional layers and the heterojunction interface properties. Such engineering strategy can optimize SnOx ETL with higher nano‐crystallinity, higher carrier density, and less defect groups, modify Sb2Se3/SnOx heterojunction with better interface performance and much desirable “spike‐like” band alignment, and also improve the Sb2Se3 light absorber layer quality with passivated bulk defects and prolonged carrier lifetime, and therefore to enhance carrier separation and transport while suppressing non‐radiative recombination. Finally, the as‐fabricated Cd‐free Mo/Sb2Se3/SnOx/ITO/Ag thin‐film solar cell exhibits a stimulating efficiency of 7.39%, contributing a record value for Cd‐free substrate structured Sb2Se3 solar cells reported to date. This work provides a viable strategy for developing and broadening practical applications of environmental‐friendly Sb2Se3 photovoltaic devices.

One-Step Hydrothermal Synthesis of Sn-Doped Sb2Se3 for Solar Hydrogen Production

“…An AC frequency of 10 kHz was applied to extract the carrier density in both CV and DLCP measurements. The carrier density from the CV measurement ( N CV ) can be extracted by the following equation .25ex2ex N C V = − 2 q ε ε 0 A 2 [ d false( C − 2 false) d V D C ] − 1 Here, q represents the elementary charge, ε represents the dielectric constant of the Sb 2 Se 3 (taken as 15.1), ε 0 is the permittivity of free space, and A is the measured area of the diode. In the DLCP measurements, the carrier density is derived from the nonlinear relationship between the change in charges (δ Q ) and the perturbation AC bias (δ V ) .25ex2ex δ Q / δ V = C 0 + C 1 δ V + C 2 ( δ V ) 2 + ··· The values of C 0 and C 1 can be obtained by fitting the capacitance versus perturbation AC bias plots with this function.…”

“…Here, q represents the elementary charge, ε represents the dielectric constant of the Sb 2 Se 3 (taken as 15.1), 44 ε 0 is the permittivity of free space, and A is the measured area of the diode. In the DLCP measurements, the carrier density is derived from the nonlinear relationship between the change in charges (δQ) and the perturbation AC bias (δV)…”