Decreasing CsPbI3 quantum size decreases charge separation and recombination
DOI: 10.1063/1.5124240
Decreasing CsPbI3 quantum size decreases charge separation and recombination lead image
Perovskite quantum dots (QDs) made with cesium lead halides have shown promise in a variety of optoelectronic applications ranging from thin film solar cells to light-emitting diodes to photocatalysis. The materials’ broad absorption spectra and stability allow them to be tuned over a wide range of wavelengths at room temperature. New work with cesium lead halide QDs examines how the size of the QD affects key parameters for determining efficiency.
Shang et al. report the effects of changing the QD size have on charge separation (CS) and charge recombination (CR) between CsPbI3 QDs and Rhodamine B (RhB) molecules. Using transient absorption spectroscopy, the group found that, by decreasing the average size of quantum dots from 11.8 nanometers to 6.5 nanometers, time constants for both CS and CR, two important measures for power conversion efficiency, decreased.
By examining CsPbI3, a representative material for other cesium lead halide perovskites that have already seen use in optoelectronics, the work looks to add new insight into the behavior of these tunable materials.
“If you do make changes to the size of the dot, we now know what change you can expect from these parameters used to determine power conversion efficiency,” said Tianquan Lian, an author on the paper.
The group found that the observed size-dependence of CS and CR rates was well explained by Marcus theory using theoretically calculated driving forces for the respective processes, molecular reorganization energies, and electronic coupling strength between the QD and RhB.
Lian said he hopes to study next how such properties change in different types of electron-accepting materials, different types of quantum dots and in different parts of solar cells.
Source: “Size dependent charge separation and recombination in CsPbI3 perovskite quantum dots,” by Qiongyi Shang, Alexey L. Kaledin, Qiuyang Li, and Tianquan Lian, The Journal of Chemical Physics (2019). The article can be accessed at https://doi.org/10.1063/1.5109894 .
