Alkali Metals Doping for High‐Performance Planar Heterojunction Sb₂S₃ Solar Cells

Abstract

Sb2S3 as a stable light harvesting material has received increasing attention for solar cell applications. To improve the device efficiency, much effort has been put into the materials synthesis, interfacial engineering, and device structure design. Here, it is demonstrated that doping of alkali metal (Li, Na, K, Rb, Cs) ions essentially affects the morphological, crystal, optical and electrical properties of Sb2S3 films. The structural and compositional analysis shows that the doping is in form of alkali metal‐sulfur chemical bond at both surface and grain boundaries of Sb2S3 films. Compared with the pristine Sb2S3, we observe that Li and Na doping are not able to improve the device efficiency, while K, Rb, and Cs notably increase energy conversion efficiency. The most effective enhancement is found in Cs‐doped Sb2S3, where the carrier concentration, crystallinity, and film formability show remarkable improvement. The device based on the Cs‐Sb2S3 film delivers a power conversion efficiency of 6.56%, which is the highest efficiency in planar heterojunction Sb2S3 solar cells, regardless of whether the films are fabricated by a solution process or thermal deposition. This research identifies that doping of heavy alkali metals is an effective approach to improve the performance of Sb2S3 solar cells.

Review of Recent Progress in Antimony Chalcogenide‐Based Solar Cells: Materials and Devices

“…Moreover, as shown in Figure , Cs‐doping strikingly enhanced the uniformity of Sb 2 S 3 films, showing very compact, smooth and large‐sized grains. Consequently, the highest efficiency has been achieved by Cs‐doping . This work further demonstrated doping strategies as efficient methods to improve absorber quality.…”

“…Consequently, the highest efficiency has been achieved by Cs-doping. [89] This work further demonstrated doping strategies as efficient methods to improve absorber quality.…”

Intrinsic Defect Limit to the Electrical Conductivity and a Two‐Step p‐Type Doping Strategy for Overcoming the Efficiency Bottleneck of Sb2S3‐Based Solar Cells

“…Therefore, to increase the carrier concentration (the electrical conductivity) and improve the performance of Sb 2 S 3 ‐based solar cells, extrinsic doping becomes necessary for passivating the detrimental recombination center defects and producing more carriers. In the past decade, many experiments tried to dope the Sb 2 S 3 to increase the conductivity . However, the efficiency has not witnessed apparent increase (stagnating at 7.5% in the past 5 years).…”

Alcohol Vapor Post‐Annealing for Highly Efficient Sb2S3 Planar Heterojunction Solar Cells

“…Compared with the mesoporous structure, planar heterojunction could avoid high‐temperature annealing and reduce interface defects . Various methods have been proposed to prepare Sb 2 S 3 films in planar heterojunction solar cells, including spray pyrolysis, chemical bath deposition, thermal evaporation, atomic layer deposition, and fast chemical approach (FCA), and so on. Among these methods, FCA is an attractive route due to its simple process and fast crystal growth .…”

“…However, the grain‐size of Sb 2 S 3 films obtained from the FCA process is relatively small. It has been reported that doping with alkali metals or ZnCl 2 can improve the grain‐size and crystallinity of Sb 2 S 3 films, and the PCE of Sb 2 S 3 solar cells was boosted . Therefore, it is important to control the morphology and crystallinity of the solution‐processed films to achieve higher efficiency.…”