利用超快雷射時間解析光譜研究- 經TOPO處理之PEA2(FAPbBr3)2PbBr4之超快動力學

研究生：謝博楊 指導教授：王立邦、籔下篤史 博士

國立清華大學物理研究所

中文摘要
鈣鈦礦發光二極體因為其良好的發光效率而備受關注，尤其是RP型態(Ruddlesden–Popper)結構的鈣鈦礦材料，可以有較大的激子束縛能，意味著輻射復合機率比較高，而非輻射的復合機率較低，發光波長也較為相近，所以被視為是有效率的發光二極體材料。然而這類的材料通常會有純度較低而影響發光效率的問題，因此在本實驗中的樣品PEA2(FAPbBr3)2PbBr4中加入表面鈍化劑：氧化三辛基膦(trioctylphosphine oxide)，期待期起到降低材料缺陷的影響。
本論文將透過超快時間解析光譜，以紫外光為超短脈衝激發光，可見光為短脈衝探測光，將所探測到的載子動態完整記錄，觀察期衰減率與生命週期。並藉由鹵化物鈣鈦礦中載子密度變化與復合率的公式求解，分析樣品PEA2(FAPbBr3)2PbBr4在加入氧化三辛基膦後的復合機制變化。我們可以觀察到PEA2(FAPbBr3)2PbBr4在經TOPO處理之後的SRH recombination下降了31.76%左右，而此回復機制的生命週期(lifetime)也有顯著的增加，這代表著經過TOPO處理後PEA2(FAPbBr3)2PbBr4受到材料內部缺陷的影響顯著的下降，達到旋塗TOPO層做為缺陷鈍化劑的目的。

Ultrafast Dynamics of TOPO-treated PEA2(FAPbBr3)2PbBr4 studied by Ultrafast time-resolved spectroscopy

Student: Po Yang Hsieh Advisor: Dr. Li Bang Wang,
Dr. Atsushi Yabushita

Department of Physics

National Tsing Hua University

Abstract
Perovskite light-emitting diodes have attracted much attention because of their good efficiency, especially the perovskite materials with RP type(Ruddlesden-Popper) structure, which can have a rather large exciton binding energy, which means higher probability of radiative recombination and lower probability of nonradiative recombination, and the emission wavelength is relatively close, so it’s considered as an efficient light-emitting diode material. However, this kind of materials usually have the problem of low purity which affects the luminous efficiency. Therefore, in this experiment, the sample PEA2(FAPbBr3)2PbBr4 was added with a surface passivation: trioctylphosphine oxide(TOPO), expecting to play a role in reducing surface state.
In this paper, through ultrafast time analysis spectroscopy, we use ultraviolet light as the pump beam, and visible light as the probe beam. And by solving the formula of carrier density change and recombination rate in halide perovskite, the recombination mechanism of PEA2(FAPbBr3)2PbBr4 was analyzed after adding trioctylphosphine oxide. We can observe that the SRH recombination decreased by about 31.76% after TOPO treatment, and the lifetime of this recovery mechanism also increased, which means after TOPO treatment, the effect of material defect decreased, which matches the purpose of spin-coating TOPO layer.

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