高量子效率二六族核殼量子點之連續離子 吸附層法合成與特性鑑定

Abstract

本論文中我們以二步驟合成法製備了六系列的二-六族半導體核-殼量子

點(硒化鎘/硫化鎘、硒化鎘/硒化鋅, 硒化鎘/硫化鎘/硫化鋅、硒化鎘/硫

化鋅、硒化鋅鎘/硫化鎘、以及硒硫化鎘/硫化鎘),本製程使用較低毒性及

低成本之前驅物(氧化鎘、硒粉、硫粉及硬脂酸鋅)取代高毒性有機金屬前驅

物並搭配常見的包覆劑(油酸、硬脂酸、十六胺、十八胺及氧化三辛基磷)於

溫和條件下進行反應,且從一系列不同反應溫度及鎘/硒比條件下合成出最

佳化硒化鎘量子點供後續的殼包覆使用。

殼的包覆採用連續離子沉積與反應製程,此法能使殼材料成功沉積在純

化過的核量子點上,同時避免殼材料同相成核,溫和的殼成長溫度(200 °C)

可以減輕在核-殼交界處合金化的現象以及螢光光譜紅位移程度。對大部分

核-殼量子點而言,其螢光光譜多呈現窄頻帶,半高寬也多小於 40 nm,上

述現象反映出令人滿意的尺寸控制表現,殼的生長大幅提升了螢光放光效

率,尤其是以三元組成的合金核為基礎的量子點,所得之核以及核-殼量子

點放出黃綠到紅的螢光,此多方面適用的合成法提供了高品質、高螢光效率

及低成本的途徑,為後續量子點顯示器及太陽能電池領域應用打開一扇大

門。

Herein, a series of II-VI semiconductor core/shell QDs were synthesized by a two-step method (CdSe/CdS, CdSe/ZnSe, CdSe/CdS/ZnS, CdSe/ZnS,CdZnSe/CdS, and CdSeS/CdS). The reaction conditions were mild by adopting less toxic and less expensive reactants (cadmium oxide, S powder, Se powder, and zinc stearate) and passivating ligands (stearic acid, oleic acid, hexadecylamine,octadecylamine and trioxylphosphine oxide) instead of hazzardous organometallic precursors. Different conditions of various reaction temperatures and feeding ratios of Cd to Se were tested to accomplish the best CdSe cores for further shell decomposition. For shell growth, successive ion layer adsorption and reaction (SILAR) method offered a successful deposition of shell materials onto purified cores to avert homogeneous nucleation. Shell grew under moderate temperature (200 °C) in order to alleviate the alloy formation between the interface of core/shell and abate serious PL emission red-shift. The resulting PL spectra exhibited sharp peaks for most core/shell QDs and FWHM less than 40 nm, indicating satisfactory control of size distribution. After shell growth, the PL QY was significantly enhanced, especially for gradient alloy ternary cores. The resulting cores and core/shell QDs emitted light from yellow-green to red colors. This versatile synthetic methodology providing highly quality, high QY, and low-cost core/shell QDs opens a door to their applications in display and solar cells.