Excitons in two-dimensional perovskites quickly dissociate into free providers beneficial for photovoltaic applications, simply as bees holding electrons and holes satisfy and different in the flowers. Credit: DICP
A research group led by Prof. JIN Shengye from the Dalian Institute of Chemical Physics ( DICP) of the Chinese Academy of Sciences exposed an ultrafast and high-yield polaronic exciton dissociation system in two-dimensional (2D) perovskites.
This research study was released in Journal of the American Chemical Society on November 3, 2021..
2D perovskites are a class of naturally formed quantum well (QW) products. The exciton binding energy in 2D perovskite is much larger (approximately hundreds of meV) than that in their 3D counterparts due to strong quantum and dielectric confinement.
It is typically believed that the photogenerated charge providers in 2D perovskites generally exist in the kind of excitons, which are hard to dissociate into totally free carriers at room temperature.
In this study, by utilizing femtosecond photoluminescence up-conversion (PL-UC) and transient absorption (TA) spectroscopy, the researchers for the very first time directly and dynamically observed the ultrafast (< < 1.4 ps) and extremely effective (> > 80%) exciton dissociation in 2D perovskites (n ≥ 2). This validated that free-carriers were the dominant provider species in 2D perovskites under room temperature, which conflicts with previous idea.
They proposed a polaron-induced exciton dissociation system, where the exciton-polarons were readily formed by strong exciton-phonon coupling as in 3D perovskites, and the polaronic screening effect led to a prominent decrease in binding energy for efficient exciton dissociation.
The researchers demonstrated that the exciton dissociation into free-carriers was a significant aspect restricting the photoluminescence quantum yield of 2D perovskites by introducing extra nonradiative provider loss.
” This work reveals a common exciton dissociation home in this class of 2D materials and provides a guideline for the design and reasonable usage of 2D perovskites in optical and optoelectronic applications,” stated Prof. JIN.
Reference: “Ultrafast and High-Yield Polaronic Exciton Dissociation in Two-Dimensional Perovskites” by Qi Sun, Chunyi Zhao, Zixi Yin, Shiping Wang, Jing Leng, Wenming Tian and Shengye Jin, 3 November 2021, Journal of the American Chemical Society.DOI: 10.1021/ jacs.1 c08900.
This research study was supported by the Ministry of Science and Technology of China, the National Natural Science Foundation of China and the Youth Innovation Promotion Association of CAS.