Unveiling Charge Transport Barriers in 2D devices with in-operando light-modulated Kelvin Probe force microscopy

Two-dimensional (2D) materials, such as transition metal dichalcogenides (TMDCs), offer significant promise for next-generation solar cells due to their unique optoelectronic properties, including high light absorption, tunable bandgaps, and mechanical flexibility. Despite these advantages, the performance of devices based on 2D materials is often limited by interfacial charge transport barriers, particularly at the metal-2D material junctions. Understanding these barriers is critical for optimizing device efficiency and advancing 2D-material-based photovoltaics. This study employs Kelvin Probe Force Microscopy (KPFM) to investigate the potential distribution across 2D-material-based devices and establish correlations with their current-voltage (I-V) behavior. The results reveal a strong correlation between the I-V characteristics and the potential profiles measured by KPFM. For devices exhibiting ohmic I-V behavior, the potential drops predominantly across the 2D material channel, with negligible potential drops at the contacts. In contrast, for devices with asymmetric I-V behavior, the potential primarily drops at the metal-semiconductor contacts, indicating significant charge transport barriers. These findings highlight the capability of KPFM to spatially resolve potential variations in operating devices, providing direct insight into the nature of charge transport at critical interfaces. By linking I-V characteristics to potential distribution, this study offers a pathway for diagnosing and mitigating interfacial losses in 2D-material-based devices.