A new metal transfer process for van der Waals contacts to vertical Schottky-junction transition metal dichalcogenide photovoltaics

TL;DR

This paper introduces a simple, lithography-free metal transfer process for making high-quality contacts to 2D transition metal dichalcogenide solar cells, significantly improving their photovoltaic performance.

Contribution

The authors develop a novel metal transfer technique that enhances contact quality in 2D TMD photovoltaics without complex lithography, enabling better device performance.

Findings

Transferred contacts show rectifying behavior and high open-circuit voltage.

Devices with transferred contacts outperform evaporated contacts in photovoltaic metrics.

The technique could enable high-power-density 2D TMD solar cells.

Abstract

Two-dimensional transition metal dichalcogenides are promising candidates for ultrathin optoelectronic devices due to their high absorption coefficients and intrinsically passivated surfaces. To maintain these near-perfect surfaces, recent research has focused on fabricating contacts that limit Fermi-level pinning at the metal-semiconductor interface. Here, we develop a new, simple procedure for transferring metal contacts that does not require aligned lithography. Using this technique, we fabricate vertical Schottky-junction $WS_2$ solar cells with Ag and Au as asymmetric work function contacts. Under laser illumination, we observe rectifying behavior and open-circuit voltage above 500 mV in devices with transferred contacts, in contrast to resistive behavior and open-circuit voltage below 15 mV in devices with evaporated contacts. One-sun measurements and device simulation results indicate that this metal transfer process could enable high-specific-power vertical Schottky-junction transition metal dichalcogenide photovoltaics, and we anticipate that this technique will lead to advances for two-dimensional devices more broadly.