低維度鈣鈦礦材料在發光二極體及光響應元件之光電特性與應用

Abstract

本論文涵蓋兩個主題的研究：一個是無藍害鈣鈦礦發光二極體的製作，另一個是兩種鈣鈦礦材料藉由旋轉塗佈法製成二維鈣鈦礦光響應元件。在無藍害鈣鈦礦發光二極體的研究中旨在透過控制低維度之〖 〖BA_2 MA_(n-1) Pb〗_n I〗_(3n+1) 的組成以製作出放出近似蠟蠋光色之發光二極體。在選擇材料的適當組成比例後，引入不同電子、電洞傳輸層進行效率量測以找出最適合之元件結構。最後，使用差溶劑處理、吹氮氣處理兩種方式修飾鈣鈦礦薄膜進而優化元件的量子效率，可將其量子效率提升至原本的1000倍。在二維鈣鈦礦光響應元件的研究中旨在將鈣鈦礦溶液透過快速簡單的旋轉塗佈法形成鈣鈦礦薄片並製成元件探究其光電特性。本研究使用兩種材料分別為：MA_3 Bi_2 I_9、Cs_3 Bi_2 I_9 ，所製作的鈣鈦礦薄片最薄僅約2nm，且可由光學顯微鏡所看到的顏色簡單辨認晶體厚度之大小。在 MA_3 Bi_2 I_9 之研究中對電學特性有較多的探討，可藉由量測電壓與電流之關係圖得到缺陷密度等材料參數，亦可由光電流與暗電流之電流差異得知 MA_3 Bi_2 I_9 晶體有製成光電導體（Photoconductor）之潛力。而〖 Cs〗_3 Bi_2 I_9 則著墨較多在其光學特性之探討。藉由量測其低溫 PL特性得知〖 Cs〗_3 Bi_2 I_9 晶體之能隙、半高寬等隨溫度的變化與傳統半導體更為相似，亦可得知如激子結合能等材料相關參數。兩種材料之晶體在光學、電學特性上所得到的成果，讓未來進行薄片之特性量測時可有所期待。This thesis covers the research of two topic: one is making blue-hazard free perovskite light-emitting diodes (PLED); the other is making low-dimensional perovskite photoconductors by spin coating.The purpose of the first topic is making PLED that emits candle-like light through controlling the composition of low-dimensional perovskite, 〖 〖BA_2 MA_(n-1) Pb〗_n I〗_(3n+1). In order to find the best PLED’s structure, we introduced hole transporting layer and electron transporting layer into PLED’s structure after choosing appropriate composition ratio of the perovskite. Lastly, the external quantum efficiency of the PLED was optimized by a thousand times through dripping antisolvent or blowing nitrogen onto the perovskite film.The purpose of the second topic is to investigate the optoelectronic properties of photoconductors made from perovskite flakes spin coated on silicon. MA_3 Bi_2 I_9 and Cs_3 Bi_2 I_9 were used in this work. The perovskite flakes with thickness of 2 nm was achieved. We can tell the thickness by observing the color of the perovskite flakes under optical microscope. In this thesis MA_3 Bi_2 I_9 had more discussion about electrical characteristics. We not only extracted the density of deep trap states by measuring current-voltage (IV) trace, but also knew that MA_3 Bi_2 I_9 crystal has the potential to be used as a photoconductor because of comparison of current in dark and light. On the other hand, Cs_3 Bi_2 I_9 had more discussion about optical properties. By measuring the temperature-dependent photoluminescence (PL), we knew Cs_3 Bi_2 I_9 is more like traditional semiconductors because the changes of PL characteristics Such as band gap, the PL spectra's full width at half maximum (FWHM), and integrated PL intensity as the temperature increases. In addition, the exciton binding energy, etc could also be extracted in this experiment. Due to optoelectronic properties of the two kinds of perovskite crystals, more tests of perovskite flakes is worth doing in the future.