CdSe 기반 양자점의 합성 및 특성평가

Abstract

최근 유기형광화합물 대신 나노크기의 결정구조 반도체인 양자점 형광체가 주목받고 있다. 양자점 형광체는 크기가 작아짐에 따라 양자구속효과에 의해 가전자대와 전도대 사이의 간격인 밴드갭이 늘어나 흡수 및 방출 파장의 변화를 유도하게 된다. 입자 크기가 다른 양자점 형광체는 양자구속효과를 통해 전 가시광 영역의 빛을 구현할 수 있어 광전자소자 및 태양전지 분야에서 활발히 연구가 진행되고 있다. 유기형광 화합물은 들뜬 상태에서 광화학반응에 의해 분해되어 광탈색이 일어나는 반면에, 양자점 형광체는 광탈색이 일어나지 않는 매우 안정하고 높은 양자효율을 가지고 있다. 그 중 CdSe 양자점은 높은 발광효율과 광안정성, 가시영역(420~710nm)의 빛을 낼 수 있는 소재로써 응용적 관심에서 가장 주목 받고 있다. 양자점 형광체는 주로 콜로이드 법에 의해 합성되며, 이 방법으로 합성된 양자점은 전구체의 종류와 농도, 성장온도 등을 제어함으로써 다양한 특성을 나타낸다. CdSe 양자점은 포스핀(PH3)을 전구체로 사용하는 콜로이드 법으로 제조되는데 포스핀은 원가가 높고 유독성이기 때문에 친환경적이고 저가인 원료를 이용하여 CdSe 양자점을 합성할 필요가 있다. 본 연구에서는 포스핀을 사용하지 않는 친환경 콜로이드 법으로 CdSe 양자점 형광체를 합성하였고 표면특성 제어를 위한 코어(CdSe)/쉘(CdS) 구조를 구현하였다. 또한 장기 신뢰성에 대한 기초 분석을 위해 코어(CdSe)의 표면 산화 거동을 실험적으로 규명하였다.|Recently, QDs have been investigated as promising optoelectronic materials because of its unique optoelectronic properties and high stability. QDs have been studied to solve the limitations of commotional optoelectronic devise. For example the luminescence wavelength can be shifted to visible wavelength range with QDs. Therefore, QDs optoelectronics can be applied into not only biochemical applications but also light emitting diodes (LEDs), laser and fluorescent biological label. The composite semiconductor nano crystals such as CdS, CdSe and ZnSe have been studied for photoluminescent QD materials. Above all, CdSe is advantageous materials because it has bright luminescence in the visible range of the optical spectrum and easily fabricable in well-dispersed nano-sized crystals. The properties of CdSe QDs core such as reaction temperature, concentrations and time can be varied using the synthetic parameters. The most of cases, CdSe QDs was synthesized by colloidal process with phosphine (PH3) precursor such as TOP, TOPO and TBP. However, conventional colloidal methods with PH3 were suitable, hazardous and pollutive. In this study, QDs are successfully synthesized using phosphine-free colloidal method under various conditions and core/shell structure is confirmed to control surface properties. Furthermore, surface oxidation behavior of core was investigated with long term reliability analysis.; Recently, QDs have been investigated as promising optoelectronic materials because of its unique optoelectronic properties and high stability. QDs have been studied to solve the limitations of commotional optoelectronic devise. For example the luminescence wavelength can be shifted to visible wavelength range with QDs. Therefore, QDs optoelectronics can be applied into not only biochemical applications but also light emitting diodes (LEDs), laser and fluorescent biological label. The composite semiconductor nano crystals such as CdS, CdSe and ZnSe have been studied for photoluminescent QD materials. Above all, CdSe is advantageous materials because it has bright luminescence in the visible range of the optical spectrum and easily fabricable in well-dispersed nano-sized crystals. The properties of CdSe QDs core such as reaction temperature, concentrations and time can be varied using the synthetic parameters. The most of cases, CdSe QDs was synthesized by colloidal process with phosphine (PH3) precursor such as TOP, TOPO and TBP. However, conventional colloidal methods with PH3 were suitable, hazardous and pollutive. In this study, QDs are successfully synthesized using phosphine-free colloidal method under various conditions and core/shell structure is confirmed to control surface properties. Furthermore, surface oxidation behavior of core was investigated with long term reliability analysis.