Research Excellence

Multiple exciton generation (MEG) is a process in which the energy of an absorbed photon can be used to create two or more electron-hole pairs in the semiconductor. It also plays an essential role in developing new solar cells and high-performance optoelectronic devices. One of the major energy losses in photon-energy conversion is that if the photon has more energy than is needed to create the electron-hole pair, the excess energy is lost as heat. How to utilize the excess energy to improve photo-conversion efficiency and achieve MEG is necessary and challenging.

An interdisciplinary team led by Dr Li MingJie of the Department of Applied Physics, Faculty of Science, recently developed high-quality halide perovskite nanocrystals with enhanced MEG. Nanocrystals (also known as quantum dots) developed by rational design can convert a high-energy photon into multiple electron-hole pairs, breaking the power conversion efficiency limit. The team successfully demonstrated that the internal quantum efficiency exceeded 100% at a low threshold by using such perovskite nanocrystals for the first time. The findings have been published in the highly influential journal Nature Photonics. Dr Li’s research has deepened the MEG mechanism’s understanding and provided valuable solutions for developing highly efficient light-harvesting techniques, including photovoltaics, photon detection, and solar-fuel production.

Learn more: https://www.nature.com/articles/s41566-022-01006-x

鈣鈦礦納米晶體中的多重激子效應以提高光電流量子效率

隨多重激子效應是指半導體吸收一個光子而產生兩個甚至多個電子電洞對的過程，對於發展新型太陽能電池及高性能光電子器件至為重要。在光電轉換的過程中，如果光子的能量超過了電子電洞對所需的能量，多餘的能量會以熱能的形式消耗掉。如何能有效地利用熱耗散這部分能量來提高光電轉換效率並產生多重激子效應，是有待解決的難題。

最近，由理學院應用物理學系李明杰博士帶領的跨學科團隊開發了具有增強多重激子效應的鹵化物鈣鈦礦納米晶體。通過合理設計的納米晶體 (或稱為量子點) 能將高能光子轉化為多個電子電洞對，突破光電轉換效率的極限。更重要的是團隊首次證明了使用這種新設計的納米晶體，內部量子效率在低閾值下能超過 100%。 這項研究獲刊載於高影響力的科技期刊《Nature Photonics》。李博士的研究不單加深了人們對多重激子效應的認識，同時為開發高效能的光捕獲技術，例如光伏、光子探測和太陽能燃料生產等，提供了重要的參考依據。

了解更多：https://www.nature.com/articles/s41566-022-01006-x