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

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 WS2 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.

Directly visualizing carrier transport and recombination at individual defects within 2D semiconductors

“…This ratio of in-plane to out-of-plane minority carrier diffusion lengths is significantly larger than reported values for n-WSe 2 generated through traditional, bulk photoelectrochemical experiments, 63 which may be attributable to the degree to which the experimental geometry is defined and the influence of defects can be controlled in the CG-TC SECCM experiments presented here. This value is, however, consistent with the broader range of studies of carrier transport in TMD materials, where mobility ratios up to ~10 7 have been reported. [63][64][65][66][67][68]…”

“…The unique optoelectronic properties of two-dimensional semiconductors (2DSCs), such as the transition metal dichalcogenides (TMDs), make them attractive candidates for use in a variety of electronic and photonic devices, including photovoltaic cells, [1][2][3][4][5][6][7] photodetectors, [8][9][10] and LEDs. 11,12 The inherent 2D structure of these materials allows them to be prepared as ultrathin films down to the monolayer limit, which can serve as flexible active layers with favorable optical properties as compared to the bulk material.…”

Robust Inorganic Hole Transport Materials for Organic and Perovskite Solar Cells: Insights into Materials Electronic Properties and Device Performance

“…A plethora of recent reports unambiguously demonstrated that OSCs based on TMDs, such as sulfides and selenides as HTLs and/or ETLs, exhibited superior performance, in terms of both PCE and stability, compared with other used materials. [310,312,313] Representative examples are discussed in this section.…”

Synthesis of two‐dimensional transition metal dichalcogenides for electronics and optoelectronics

“…E, Simulated I ‐ V characteristics of the fully optimized WS 2 device. C‐E, Reproduced with permission from Reference 218. F, Schematic illustration of the vertical WSe 2 /MoS 2 device with the WO x layer.…”