OPTICAL PROPERTIES AND PHOTOEXCITED CARRIER DYNAMICS OF CsPb(IxBr1-x)3 PEROVSKITE QUANTUM DOTS
Hironobu Yasuda a
a University of Electro-communications
Poster, Hironobu Yasuda, 145
Publication date: 23rd October 2018

Metal halides perovskites (PVK), such as organic-inorganic hybrid CH3NH3PbI3, have attracted much interest as optical absorption materials in solar cells, of which the power conversion efficiency has reached over 23%. On the other hand, quantum dots (QDs) have many unique properties compared to the bulk materials. Therefore, the perovskite QDs (PVK QDs) can combine the advantages of both the PVK and the QDs and they have showed higher optoelectronic properties [1]. Among the PVK QDs, CsPbX3 (X: I, Br, Cl) QDs, which have the great chemical robustness, have attracted more and more attention, because the inorganic QDs are more stable against heat and thus can be applied to various fields, such as light emitting diode, laser and solar cells. In addition, it is very interesting that the photoluminescence quantum yield (PLQY) and the PL lifetime are found to depend on X largely, especially in the case of CsPb(IxBr1-x)3 QDs [2]. However, the physical mechanism is still unclear. Therefore, here we investigate the relationship between the optical properties and the x in the CsPb(IxBr1-x)3 QDs. We prepared the colloidal CsPb(IxBr1-x)3 QDs and then studied the optical absorption and PL spectra, the PLQY and the photoexcited carrier dynamics for different x (i.e., different value of I/Br). Our results show that the PLQY decreases and both the optical absorption and PL spectra have blue shifts as the composition rate of Br increases under the same QD preparation temperature. Moreover, from the time-resolved PL (TRPL) spectra and the PLQY, we find that the non-radiative recombination time decreases greatly with the Br composition rate increasing at room temperature. This result indicates that increasing the Br composition rate in the perovskite crystal structure induce more non-radiative recombination centers in the QDs, which results in the PLQY reduction. In this research, we have quantitatively clarified the relationship between the PLQY and the non-radiative recombination in CsPb(IxBr1-x)3 QDs and their dependence of x. The mechanism behind these phenomena is now under study and will be reported soon.

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