Impact of $Al_2O_3$ Passivation on the Photovoltaic Performance of Vertical $WSe_2$ Schottky Junction Solar Cells

TL;DR

This study enhances WSe2 Schottky junction solar cells by optimizing thickness and applying Al2O3 passivation, leading to significant improvements in efficiency, EQE, and open circuit voltage.

Contribution

It demonstrates that Al2O3 passivation significantly improves the photovoltaic performance of WSe2 Schottky solar cells, with optimized device design and surface treatments.

Findings

Al2O3 passivation increases EQE by up to 29.5% at 410 nm

Optimized WSe2 thickness improves device performance

Device achieves VOC of 380 mV and JSC of 10.7 mA/cm^2

Abstract

Transition metal dichalcogenide (TMD) materials have emerged as promising candidates for thin film solar cells due to their wide bandgap range across the visible wavelengths, high absorption coefficient and ease of integration with both arbitrary substrates as well as conventional semiconductor technologies. However, reported TMD-based solar cells suffer from relatively low external quantum efficiencies (EQE) and low open circuit voltage due to unoptimized design and device fabrication. This paper studies $Pt/WSe_2$ vertical Schottky junction solar cells with various $WSe_2$ thicknesses in order to find the optimum absorber thickness.Also, we show that the photovoltaic performance can be improved via $Al_2O_3$ passivation which increases the EQE by up to 29.5% at 410 nm wavelength incident light. The overall resulting short circuit current improves through antireflection coating, surface doping, and surface trap passivation effects. Thanks to the ${Al_2O_3}$ coating, this work demonstrates a device with open circuit voltage ($V_{OC}$) of 380 mV and short circuit current density ($J_{SC}$) of 10.7 $mA/cm^2$. Finally, the impact of Schottky barrier height inhomogeneity at the $Pt/WSe_2$ contact is investigated as a source of open circuit voltage lowering in these devices