WS2: A New Window Layer Material for Solar Cell Application

Md Khan Sobayel Bin Rafiq,Nabeel H Alharthi,N Amin,Badariah Bais,Monis Luqman,Md Akhtaruzzaman,Hamad F Alharbi,Yahya S Alharthi,Afida Ayob

doi:10.1038/s41598-020-57596-5

Abstract

Radio frequency (RF) magnetron sputtering was used to deposit tungsten disulfide (WS2) thin films on top of soda lime glass substrates. The deposition power of RF magnetron sputtering varied at 50, 100, 150, 200, and 250 W to investigate the impact on film characteristics and determine the optimized conditions for suitable application in thin-film solar cells. Morphological, structural, and opto-electronic properties of as-grown films were investigated and analyzed for different deposition powers. All the WS2 films exhibited granular morphology and consisted of a rhombohedral phase with a strong preferential orientation toward the (101) crystal plane. Polycrystalline ultra-thin WS2 films with bandgap of 2.2 eV, carrier concentration of 1.01 × 1019 cm−3, and resistivity of 0.135 Ω-cm were successfully achieved at RF deposition power of 200 W. The optimized WS2 thin film was successfully incorporated as a window layer for the first time in CdTe/WS2 solar cell. Initial investigations revealed that the newly incorporated WS2 window layer in CdTe solar cell demonstrated photovoltaic conversion efficiency of 1.2% with Voc of 379 mV, Jsc of 11.5 mA/cm2, and FF of 27.1%. This study paves the way for WS2 thin film as a potential window layer to be used in thin-film solar cells.

Highlights

Radio frequency (RF) magnetron sputtering was used to deposit tungsten disulfide (WS2) thin films on top of soda lime glass substrates
WS2 is more abundant in the Earth’s crust, cheaper, and less toxic compared to other transition metal dichalcogenides (TMDCs) materials, the development of WS2 in thin-film solar cells remains in its infancy compared with similar photovoltaic materials
To investigate the suitable application of WS2 in solar cells, we extensively studied the morphological, structural, and optoelectrical properties of WS2 deposited by RF magnetron sputtering under different deposition powers

Summary

Introduction

Radio frequency (RF) magnetron sputtering was used to deposit tungsten disulfide (WS2) thin films on top of soda lime glass substrates. The deposition power of RF magnetron sputtering varied at 50, 100, 150, 200, and 250 W to investigate the impact on film characteristics and determine the optimized conditions for suitable application in thin-film solar cells. CdS is widely used as a window or buffer layer material in photovoltaic devices due to its suitable bandgap and enhancement properties in the interface chemistry between light absorber and window layer during fabrication. As radiofrequency (RF) magnetron sputtering is a plasma- or ion-assisted deposition process, the slightest variation in deposition parameters may cause changes in structure and bonding of the deposited material[27,28] Such changes may lead to both advantageous and detrimental effects for photovoltaic application. To investigate the suitable application of WS2 in solar cells, we extensively studied the morphological, structural, and optoelectrical properties of WS2 deposited by RF magnetron sputtering under different deposition powers. The study aimed to eliminate pinholes in sputtered films to improve the stability and efficiency of the solar cell device

Methods

Results

Conclusion