二維層狀鈣鈦礦之光激螢光研究

Photoluminescence Study of Two Dimensional Alkylammonium Lead Iodide Perovskites

林昌緯(Chang-Wei Lin)

指導教授 ： 安惠榮

國立交通大學/電機學院/光電工程系所/碩士(2019年)

摘要

近年來，有機-無機複合型鈣鈦礦材料展現出了極佳的光電特性，因此我們研究了四種鈣鈦礦，三維的MAPbI3與二維的EAPbI3、(PA)2PbI4以及(BA)2PbI4。我們發現MAPbI3會在160K發生正交-四方的相位轉變；(BA)2PbI4與(PA)2PbI4則是分別在280K與210K發生無序-有序的相位轉變；EAPbI3在我們觀察的溫度範圍內沒有發現相位轉變。我們利用瓦西尼、魯丁與阿瑞尼斯擬合從光激螢光光譜中得到四種材料的熱係數大約為3×10-4 eV/K，MAPbI3、EAPbI3、(PA)2PbI4、(BA)2PbI4的束縛能分別為59、33、102、314 meV。最後，我們發現(PA)2PbI4光譜中明很強的寬帶輻射是由於晶格面為(110)方向排列所造成。未來在進行二維鈣鈦礦的研究時，我們需要進一步去了解晶格方向對材料發光特性的影響。

關鍵字

二維鈣鈦礦 ； 光激螢光

並列摘要

Organic-inorganic hybrid perovskites are known to have excellent optoelectronic properties such as efficient full spectrum solar energy absorption and become one of the most promising photovoltaic materials to replace silicon for highly efficient and low-cost optoelectronic devices. Recent attention is directed to layered two-dimensional perovskites, in which inorganic halides are separated by aromatic alkylammonium cations. The strong quantum confinement in this layered structure exhibits strong excitonic behavior and the fast excitonic recombination in these layered perovskites enables the strong photoluminescence (PL) at a various visible spectral range. In this work, we have investigated the optical properties including thermal evolution of emission for three alkylammonium lead iodide perovskites, ethylammonium (EAPbI3), propylammonium [(PA)2PbI4], and butylammonium lead iodides [(BA)2PbI4]. A discrete PL peak shift is observed for (PA)2PbI4 and (BA)2PbI4 at temperatures of 210 and 280 K, respectively, which is due to the disorder-to-order phase transition for layered perovskites. The binding energy calculated from temperature dependence of PL is as large as 314 meV for (BA)2PbI4, implying the exciton confinement in layered structures. In addition to excitonic emission, an ultrabroad emission with a large Stokes shift is observed for all layered perovskites and especially, it dominates the emission of (PA)2PbI4 grown in (110) direction. Excitation power dependence of broadband emission shows a linear relation, indicating that strong broadband emission from layered perovskites is attributed to the trap state which is originated not from the defects in structures, but from the photoexcitation-induced lattice deformation. This broadband emission is commonly observed for layered lead-halide perovskites whose octahedral cage can be easily deformed and result in the self-trapped exciton emission.

並列關鍵字

perovskite ； Photoluminescence

參考文獻

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