Flexible High‐Performance Photovoltaic Devices based on 2D MoS₂ Diodes with Geometrically Asymmetric Contact Areas

Abstract

Optoelectronic performance of 2D transition metal dichalcogenides (TMDs)‐based solar cells and self‐powered photodetectors remain limited due to fabrication challenges, such as difficulty in doping TMDs to form p–n junctions. Herein, MoS2 diodes based on geometrically asymmetric contact areas are shown to achieve a high current rectification ratio of ≈105, facilitating efficient photovoltaic charge collection. Under solar illumination, the device demonstrates a high open‐circuit voltage (Voc) of 430 mV and a short‐circuit current density (Jsc) of −13.42 mA cm−2, resulting in a high photovoltaic power conversion efficiency (PCE) of 3.16%, the highest reported for a lateral 2D solar cell. The diodes also show a high photoresponsivity of 490.3 mA W−1, and a large photo detectivity of 4.05 × 1010 Jones, along with a fast response time of 0.8 ms under 450 nm wavelength at zero bias for self‐powered photodetection applications. The device transferred on a flexible substrate shows a high photocurrent and PCE retentions of 94.4%, and 88.2% after 5000 bending cycles at a bending radius of 1.5 cm, respectively, demonstrating robustness for flexible optoelectronic applications. The simple fabrication process, superior photovoltaic properties, and high flexibility suggests that the geometrically asymmetric MoS2 device architecture is an excellent candidate for flexible photovoltaic and optoelectronic applications.

High‐Speed Waveguide‐Integrated InSe Photodetector on SiN Photonics for Near‐Infrared Applications

“…[26] Additionally, the asymmetric contact geometries, defined as the difference in the contact area between the InSe flake and the metals on both sides, may result in a rectifying behavior despite the symmetric metal electrode configuration. [27] This has been reported previously in InSe and other 2D materials, where a net photocurrent at zero bias is observed enabling a self-powered photodetector. [19a,19b] The generated photocurrents (I ph = I light -I dark ) under different powers as a function of the applied voltage are depicted in Figure 3b.…”

Polarization-Sensitive Self-Powered Schottky Photodetector with High Photovoltaic Performance Induced by Geometry-Asymmetric Contacts

“…45,46 In our asymmetric contact 2D ReSe 2 device, the energy level introduced by the interface state is below ReSe 2 , which can trap holes at the interface. 28,29 The accumulated holes at both sides of region A and region B owing to the existence of interface states would modify the local potential profile, and thus, the Schottky barrier height can be lowered. 47,48 Therefore, the difference in the number of interface states under the asymmetric electrode contact area is one of the important parameter factors affecting the Schottky barrier heights.…”

“…At the same time, R (EQE) decreases from 379 mA/W (63.49%) to 169.6 mA/W (33.18%) as the power density increases from 8.35 to 144.2 mW/cm 2 because of prominent carriers' nonradiative recombination caused by defect energy levels. 28,66 Noise equivalent power (NEP) and D* describe the detector sensitivity, showing the capability of detecting weak light signals. These can be defined by the following equations:…”

“…Interestingly, the surface potential difference of region A 2 /region B 2 is higher than that of region A 1 /region B 1 , which may be derived from the process of carrier diffusion of ReSe 2 from the Au electrode to the channel center . The surface potential difference for device#1 in different regions reveals the Schottky barrier height difference, which is favorable since the excellent photovoltaic performance can be induced by the geometry-asymmetric contacts. − …”

“…While the P increases from 15.07 to 144.2 mW/cm 2 , α is fitted to be 0.72 (<1). The sublinear behavior indicates the trapped centers are filled by the continuously generated photocarriers and the recombination probability of photogenerated carriers increases, which can be seen in other p–n and asymmetric photodiodes. − , Theoretically, the β value can be divided into two categories: β = 1 represents monomolecular recombination (Shockley–Read–Hall recombination) and β = 2 corresponds to bimolecular recombination (Langevin). The β value in our ReSe 2 Schottky device is calculated to be 1.06 (close to 1), indicating that the Shockley–Read–Hall recombination caused by deep levels and surface dangling bonds plays a crucial role. , V OC reaches its maximum value of 0.14 V at P = 45.36 mW/cm 2 .…”