Researchers at the University of California, Riverside, have made a groundbreaking advancement in the field of material science and optoelectronics by unveiling a novel imaging technique. This innovative method allows scientists to visualize and differentiate the ways in which sophisticated materials utilized in solar panels and light sensors convert light into electrical energy. The implications of this discovery are profound, potentially paving the way for the development of faster, more efficient electronic devices, and enhancing existing technologies in solar energy and optical communications.
The research, led by Associate Professors Ming Liu and Ruoxue Yan from UCR’s Bourns College of Engineering, was published on July 30 in the esteemed journal “Science Advances.” The study introduces a three-dimensional imaging approach capable of distinguishing between two fundamental mechanisms through which light is transformed into electricity in quantum materials. This breakthrough presents a significant leap in our understanding of how these materials can be engineered to optimize their performance.
The first mechanism identified is the photovoltaic (PV) effect, a process well-known in the realm of solar panel technology. It involves the absorption of incoming photons which liberate electrons within a semiconductor, thereby generating an electrical flow. This effect is critical to the functionality of solar panels, but its fundamental workings are much more complex than previously understood. The PV effect plays a vital role in harnessing solar energy, and the new imaging method enables researchers to observe its operation in real-time.
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Conversely, the second mechanism is known as the photothermoelectric (PTE) effect—a process less common in discussions of solar technology but equally crucial, particularly in small-scale electronic devices. The PTE effect occurs when light energy increases the thermal energy of electrons in a material. This excess thermal energy causes the electrons to migrate from warmer areas to cooler areas, creating an electric current as they flow. The interaction between the PTE and PV effects can influence device efficiency, but this intricate balance had not been previously visualized, marking a significant gap in current scientific understanding.
The researchers specifically focused on nanodevices fabricated from molybdenum disulfide (MoS₂), a two-dimensional semiconductor material composed of just a few atomic layers. This material has attracted considerable attention due to its exceptional optical and electrical properties, positioning it as a promising candidate for future electronic applications. The team successfully employed a specialized scanning method that directs light through the tip of an atomic-force microscope, which allowed them to discern the spatial distribution of the PV and PTE effects with astounding precision, even down to the nanometer scale.
The findings of their research challenged previously held assumptions. While the occurrence of the PV effect at the junction between gold electrodes and MoS₂ was anticipated, the researchers discovered that the PTE effect extended significantly farther into the material than anticipated. This revelation indicates that heat-driven effects can significantly influence electrical output—not just around the immediate area of metal contacts, as previously thought, but across much larger surface areas within the material. This discovery invites a reevaluation of how heat management impacts the design and functionality of nanoscale devices.
In a surprising twist, the research team found that introducing a thin layer of hexagonal boron nitride (h-BN) atop the MoS₂ enabled them to manipulate the flow of heat within the material. By carefully redirecting heat flow, they maximized the PTE effect, effectively aligning temperature fluctuations with the material’s response to heat and enhancing current production. This counterintuitive approach challenges conventional wisdom, as the prevailing strategy in nanodevice engineering has generally centered on localizing heat to avoid adverse effects on performance.
To accurately isolate and analyze the contributions of the PV and PTE effects, the researchers developed an innovative analytical technique. This method involved adjusting the distance between the scanning microscope tip and the sample while monitoring changes in the current signal. By employing multi-order harmonic analysis, the team was able to differentiate between the two mechanisms for the first time in a real-world setting. This analytical advancement enhances the methodology available for future research and sets the stage for engineered improvements in device efficiency.
The implications of this work extend beyond academic curiosity; they signal potential evolutions in the manufacture of light-detecting components used in fiber-optic communication systems. With the ongoing miniaturization of these systems, the management of heat has become increasingly critical. In addition, this research could lead to more effective solar power technologies, particularly those designed to capture both ambient light and thermal energy.
Ming Liu expressed enthusiasm about the research outcomes, remarking on the prospects of fine-tuning photodetectors’ performance through the careful management of heat flow. This insight could catalyze new design strategies for optoelectronic devices, opening avenues for innovation in renewable energy and next-generation electronics.
The collaborative nature of the study underscores the diversity and richness in the scientific community, with contributions from Liu’s graduate student, Da Xu, serving as the lead author. The research team included several co-authors from UCR, further emphasizing the multidisciplinary approach taken in this investigation. Notably, they also collaborated with Takashi Taniguchi from Japan’s National Institute for Materials Science, showcasing the global effort that is often essential in advancing scientific knowledge.
As the investigation into the interactions of light, heat, and electricity within these exceptional materials continues, Liu anticipates many more discoveries. The realm of optoelectronic applications is poised for transformative progress, with the potential to rethink how we harness energy and integrate new materials into everyday technology.
In summary, this research illuminates the complex interplay between light, heat, and electricity in novel materials, revealing opportunities for enhanced energy conversion and offering a foundation for future technological advancements. With ongoing investigations into these extraordinary materials, scientists are excited to chart the unexplored territories of quantum materials and their applications in the realms of energy and communication.
Subject of Research: Not applicable
Article Title: Deciphering photocurrent mechanisms at the nanoscale in van der Waals interfaces for enhanced optoelectronic applications
News Publication Date: 30-Jul-2025
Web References: http://dx.doi.org/10.1126/sciadv.adv7614
References: Not applicable
Image Credits: UC Riverside
Keywords
optoelectronics, nanodevices, solar energy, light sensors, molybdenum disulfide, hexagonal boron nitride, photovoltaic effect, photothermoelectric effect, material science, energy conversion, quantum materials, heat management.
Tags: advanced imaging techniques in material scienceelectrical energy generation from lightenhancing optical communication technologiesimplications of material science in solar energyinnovative solar technologiesmechanisms of light to electricity conversionoptoelectronics research breakthroughsphotovoltaic energy generationquantum materials for energy conversionsolar panel efficiency improvementsthree-dimensional imaging in photovoltaics