New technology boosts performance of thin-film optical sensors and solar cells
Team led by Professor Chul-Ho Lee of KU-KIST Graduate School of Converging Science and Technology develops high-performance, atomically thin optoelectronic device
Results published in prestigious nanoscience journal Nano Letters
▲ From left: Professor Chul-Ho Lee, graduate student Seunghoon Yang
A research team led by Professor Chul-Ho Lee (advisor to first author Seunghoon Yang, integrated master’s and doctoral program) of the KU-KIST Graduate School of Converging Science and Technology at Korea University succeeded in developing technology to significantly boost the performance of optoelectronic devices based on 2D semiconductor p-n heterojunctions with atomic thickness. The project was part of a joint study with teams under Professor Gwan-Hyoung Lee of Seoul National University and Professor Suklyun Hong of Sejong University.
The team formed a p-n heterojunction* from the interlayering of a p-type semiconductor WS₂ and n-type semiconductor MoS₂, and lowered the interfacial contact resistance by introducing a charge transport layer (WOx) for hole extraction. The improved charge transfer and collection capabilities contributed to enhancing power conversion efficiency (0.7% → 5.0%).
* The device comprises a p-n heterojunction made up of p-type and n-type semiconductor material having different electrical properties, and electrical signals or energy are produced by absorbing external light such as sunlight.
The significance of the study lies in effectively lowering the interfacial contact resistance, a key factor that determines the performance of 2D-semiconductor-based optoelectronic devices, proposing a new method of improving efficiency without damaging the active semiconductor layer, and providing theoretical verification. The results will aid in enabling the development of high-performance, ultra-thin optoelectronic devices in transparent and flexible forms, thus opening new possibilities in display, solar cells, and mobile/wearable devices.
▲ Schematic illustration and cross-sectional TEM image of p-n heterojunction of 2D semiconductor, improved optical power of WOx/WSe₂ junction, and band diagram of the heterojunction device.
Supported by the National Research Foundation of Korea (NRF-2017R1A5A1014862 (SRC Program: vdWMRC Center), 2017R1D1A1B03035441, and 2018M3D1A1058793), the KU-KIST School Project, and a Korea University grant, the study was led by the research team under Professor Chul-Ho Lee (advisor to first author Seunghoon Yang, integrated master’s and doctoral program) of the KU-KIST Graduate School of Converging Science and Technology at Korea University. Other participants were Professor Hong-gyu Park (Korea University), Professor Gwan-Hyoung Lee (Seoul National University), Professor Suklyun Hong (Sejong University), and Hu Young Jeong (Ulsan National Institute of Science and Technology).
In recognition of the vast possibilities of high-performance optoelectronic devices built on 2D semiconductors, the results were published in Nano Letters (Impact Factor: 12.28), a leading journal in materials and nanoscience, on March 19.
* Title of paper: Monolithic Interface Contact Engineering to Boost Optoelectronic Performances of 2D Semiconductor Photovoltaic Heterojunctions, doi.org/10.1021/acs.nanolett.9b05162
* Author information: Twelve authors including Seunghoon Yang (first author, Korea University), Professor Hong-gyu Park (co-author, Korea University), Professor Hu Young Jeong (co-author, UNIST), Professor Suklyun Hong (co-corresponding author, Sejong University), Professor Gwan-Hyoung Lee (co-corresponding author, Seoul National University), and Professor Chul-Ho Lee (corresponding author, Korea University)