無機鈣鈦礦奈米材料CsPbI3動力學相轉變反應之探討

Abstract

全無機鈦礦材料有高的吸收係數、直接能隙、可見光範圍的能隙與雙極性等優點，做為太陽能電池、發光二極體與光感測器元件應用都有很好的成果，成為近年來重要發光材料之一。但是在水氧環境下穩定性不佳，從原本良好光學活性立方晶系結構相轉變成幾乎沒有光學活性斜方晶系，因此本實驗利用小分子的六甲基二矽硫烷置換原本主要配體油酸，首次以動力學的觀點來探討全無機鈦礦奈米材料相轉變反應，藉由不同溫度下加入去離子水到不同配體溶液中，加速相轉變反應，並進行螢光測試來計算反應常數與反應活化能，本研究主要透過反應活化能配合X 光繞射光譜與穿透式電子顯微鏡圖證明六甲基二矽硫烷配體材料有較佳的穩定性，並可由此配體置換實驗結果推測，之所以會發生相轉變反應是由於奈米材料表面配體不穩定，使得奈米晶體變為無光學活性相，之後將兩種材料製作成光感測器元件，六甲基二矽硫烷配體CsPbI3材料元件相較於一般油酸配體有更好的穩定性表現。 關鍵字: 全無機鈣鈦礦奈米晶體;動力學相轉變反應;相轉變活化能Colloidal inorganic perovskite CsPbI3 nanocrystals have attracted broad attention because their outstanding optoelectronic applications in the fabrication of solar cell, light emitting diode and photodetector devices. The remarkable optoelectronic properties of CsPbI3 nanocrystals typically observed in cubic phase. However, it undergoes rapid phase transformation from cubic to orthorhombic phase by simple moisture exposure. In this study, the cubic phase of the CsPbI3 nanocrystals well stabilized for long duration by introducing bis(trimethylsilyl)sulfide as a unique surfactant in the synthesis procedure. The reaction kinetics and phase transformation of the CsPbI3 nanocrystals were systemically investigated by in-situ photoluminescence and X-ray diffraction measurements. From activation energy study, the bis(trimethylsilyl) sulfide-CsPbI3 (TMS-CsPbI3) nanocrystals exhibits largely enhanced stability than the typical oleic acid-CsPbI3 (OA-CsPbI3) nanocrystals. Furthermore, the stability and performance of the photodetector devices fabricated with TMS-CsPbI3 nanocrystals is highly improved as compared to the OA-CsPbI3 nanocrystals. The enhanced stability of the TMS-CsPbI3 be attributed to the stronger bonding between bis (trimethylsilyl) sulfide and CsPbI3 nanocrystals.

Keywords: phase transformation reaction , perovskite (CsPbI3) nanocrystals, perovskite photodetector