Tsinghua University develops efficient and stable perovskite quantum dot deep red light devices

Semiconductor quantum dots have the advantages of high quantum yield, narrow emission spectrum, and compatibility with solution processes. They have shown broad application prospects and enormous economic value in the field of optoelectronic materials and devices, and related research has won the Nobel Prize in Chemistry in 2023.

Compared with traditional II-VI and III-V quantum dots (such as CdSe, CdS, InP, etc.), perovskite quantum dots have unique advantages such as low cost, simple synthesis process, and continuously tunable spectra, and have attracted much attention in recent years. The external quantum efficiency of light-emitting devices based on perovskite quantum dots has been improved to over 20%, reaching the threshold for commercial applications. However, due to the poor stability of perovskite quantum dots, the operating life of light-emitting devices is only tens or hundreds of hours, which hinders their further industrialization.

Perovskite quantum dots require ligands to bind to their surface in order to maintain colloidal stability. However, during the growth, purification, film formation, and storage of perovskite quantum dots, highly dynamic and unstable ligands on the surface are prone to detachment, resulting in insufficient coordination of surface atoms, an increase in unsaturated and dangling bonds, and non coordinated atoms on the surface easily binding to other atoms, leading to aggregation or Oswald ripening of perovskite quantum dots, producing various defects and further affecting their luminescence performance and stability.

Recently, the team led by Ma Dongxin from the Department of Chemistry at Tsinghua University proposed a molecular induced quantum dot maturation control strategy, achieving efficient and stable perovskite quantum dot deep red light devices. The team has designed a series of bidentate organic small molecules with small size and molecular flexibility, which can adhere to the surface of perovskite quantum dots by twisting their own structure, interact with mismatched Pb2+, maintain a stable surface state, suppress the adverse aging and aggregation phenomena of perovskite quantum dots, reduce the density of surface defect states, and improve quantum yield.

Figure 1. Schematic diagram of molecular induced quantum dot maturation control strategy

The team has constructed a deep red light device based on high-performance perovskite quantum dots, with a luminescence peak at 686nm and an external quantum efficiency of up to 26.0%. The device exhibits excellent operational stability, with a half-life of 310 minutes at a constant high current density of 13.3mA cm-2, and a half-life of up to 10587 hours at an initial radiance of 190mWSr-1m-2. In addition, this perovskite quantum dot solution exhibits excellent storability, with external quantum efficiencies of 21.7% and 20.3% for devices constructed from the solution after one and three months of storage, respectively.

The above results indicate that the molecular induced quantum dot maturation control strategy proposed in the paper can effectively improve the efficiency and stability of perovskite quantum dot light-emitting devices, making them practical and promising in high-definition displays and biomedical treatments.

Figure 2. Optoelectronic properties of perovskite quantum dot light-emitting devices

Figure 3. Stability of perovskite quantum dot light-emitting devices

The related research results, titled "Molecular Induced Ripening Control in Perovskite Quantum Dots for Efficient and Stable Light Emitting Diodes", were published on March 14th in Science Advances.

Chen Jiawei, a postdoctoral fellow in the Department of Chemistry at Tsinghua University, Chen Shulin, an associate professor at the School of Semiconductors (School of Integrated Circuits) at Hunan University, and Liu Xiangyu, a doctoral student in the Department of Chemistry at Tsinghua University, are the co first authors of the paper. Associate Professor Ma Dongxin from the Department of Chemistry at Tsinghua University is the corresponding author of the paper, and the Department of Chemistry at Tsinghua University is the first communication unit. The research has received support from the National Natural Science Foundation of China's Youth Fund, Tsinghua University's Solid Science Program, the Chinese Postdoctoral Program, the Chinese Postdoctoral Special Fund, the National Postdoctoral Researcher Program, and the Tsinghua University's "Water and Wood Scholars" Program.

Source: opticsky