鈣鈦礦量子點應用於發光二極體之製備與特性分析

Abstract

本研究分成兩部份分別透過摻雜銫離子與微波輔助製程改善鈣鈦礦材料之穩定性。第一部份首先透過紫外線可見光光譜分析結果了解有機-無機鈣鈦礦量子點摻雜銫離子之能隙變化，接著透過螢光光譜分析了解有機-無機鈣鈦礦量子點摻雜銫離子能夠有效提升材料之光學特性。並透過忍耐因子與八面體因子之理論計算搭配材料之光致發光之穩定性量測結果，解釋有機-無機鈣鈦礦量子點摻雜銫離子後有效提升材料之環境穩定性。並藉由時間解析光致發光光譜儀量測可得有機-無機鈣鈦礦量子點摻雜銫離子可以有效降低材料之非輻射釋能。最後透過發光二極體之光激發光光譜測試，並得材料之色度空間作表與色域面積。 第二部份則透過微波輔助製程改善材料之光學特性。首先藉由參數與光致發光光譜量測訂定比較參數，並藉由掃描式電子顯微鏡了解微波輔助製程對於材料形貌與二次粒子粒徑之影響。藉由紫外線/可見光光譜分析結果確認材料特徵峰，實驗結果搭配Urbach energy之計算確認微波輔助製程改善可以降低傳統製程之材料缺陷。並以低溫光致發光光譜輔以非輻射釋能之理論證實微波輔助製程材料之內部缺陷較傳統加熱製程少。透過高溫環境穩定性測試了解材料之高溫穩定性。最後再將材料以發光二極體作為激發光源之光譜測試了解材料之空間色度座標與色域面積。

The perovskite quantum dots (PQDs) have been utilized as the essential materials in photovoltaics, and light-emitting diodes due to tunable emission, narrow bandwidth, high absorption coefficient, and photoluminescence quantum yield. However, intrinsic instability of PQDs hinders practical applications. Therefore, the present research work focuses to improve the stability via doping and new synthesis techniques for the realization of practical applications. In the first part, the synthesis of FAPbBr3 was discussed in details and the change in energy band gap after doping with Cs+ ions in place of FA+ sites was realized. Fluorescence spectroscopy and ultraviolet-visible light spectroscopy were utilized to understand the effectiveness of doping in improving the optical properties PQDs. Time-resolved photoluminescence spectroscopy was used to predict the effective reduction of non-radiative energy release of PQDs after doping for the enhancement of optical properties. Moreover, the doping of Cs+ ions enhanced the stability of FAPbBr3 PQDs. The enhancement of stability was grasped through the theoretical estimation of tolerance and octahedral factors. Finally, the PQDs and commercial red phosphors were utilized to coat on a blue LED chip for the fabrication of light-emitting diodes. The resultant color quality and the color gamut indicated the suitability of the present materials for practical application. The first part concluded that the doping of Cs+ ion was an effective way to improve the stability and optical properties of PQDs. In the second part, Cs-based PQDs were synthesized. A comparative analysis of the optical properties and the stability was carried out for Cs based PQDs synthesized via conventional heating approach and microwave-assisted approach. Improved optical properties for the microwave-assisted process was found from fluorescence and ultraviolet-visible light spectroscopy measurements. The influence of the microwave-assisted process on the morphology of the material and particle size distribution was understood by the scanning electron microscope. Time-resolved photoluminescence spectroscopy and Urbach energy calculations endorsed that the improvement of optical properties and the stability of the samples synthesized via the microwave-assisted process was owing to the reduction of non-radiative energy transfer and defects. Low-temperature photoluminescence spectroscopy proved that the internal defects of the samples synthesized via the microwave-assisted process were less than that of the traditional heating process. The high-temperature stability of the materials was checked through the high-temperature environment stability test. Finally, the best PQDs were utilized to coat on a blue LED chip for the fabrication of light-emitting diodes. The resultant color quality and color gamut indicated the suitability of present materials for practical applications. The second part concludes that the microwave-assisted synthesis was an effective synthesis way to improve the stability and optical properties of PQDs.