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Solution Processed Inorganic Nanocrystals for Solar Energy Conversion

초록/요약

Nanomaterials, unlike their bulk part, possess new properties that can be customized for a variety of applications by controlling their size and shape. Inorganic semiconductor nanomaterials are ideal candidates for optoelectronic devices because of the broad range of functions and the specific electronic and optoelectronic properties. Nanocrystals can be synthesized using a solution method, which offers sufficient control over the morphology of the crystals. In addition, solution-based processes provide substantial cost reductions for the fabrication of electronic and optoelectronic devices. This study covers the synthesis of solution-based nanomaterials, their application to various optoelectronic devices and their characterization. Firstly, a low-cost method to fabricate counter electrodes of QDSSC(quantum dot sensitized solar cell) by direct deposition of colloidal-Cu2S nanocrystals onto conducting FTO glass using drop-casting was explored. Cu2S- nanocrystal films provide greater surface area, thus improving catalytic activity for the redox couple and enhancing the final photovoltaic performance. Secondly, the electrical and chemical performance of various DSSCs(dye sensitized solar cell) fabricated with conventional Pt-based and heat-treated CZTS(Cu2ZnSnS4) counter electrodes without involving sulfurization were investigated. Thirdly, we present a new synthesis method for the fabrication of hybrid metal-Cu2S (M=Pt, FePt) nanocrystals (HNs). Metal nanoparticles (M=Pt, FePt) act as seeds for the growth of the dumbbell shaped metal-Cu2S HNs. The metal-Cu2S HNs were investigated in photocatalytic hydrogen generation as effective co-catalysts on TiO2. Lastly, we developed a TiO2-CuSbS2 (CAS) composite based on a new and facile solution synthesis approach for photocatalytic hydrogen production.

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초록/요약

나노 소재는 동일한 물질 내에서도 벌크 소재와는 매우 다른 물리적 화학적 전자기적 광학적 특성을 갖게 된다. 입자크기가 나노미터 수준으로 미세해지면 물질 자체의 전자 및 결정구조의 변화, 입자의 표면적 증가에 따른 표면 물성의 증가 등으로 인하여 새로운 특성을 가지게 되기 때문이다. 따라서 최근 무기 나노 소재의 크기와 모양을 조절하여 유도된 광범위한 기능과 촉매 및 광전자 특성을 다양한 디바이스에 적용하는 연구가 수행되고 있다. 본 연구에서는 용액 기반 나노 소재를 합성하고 다양한 광전자 소자에 적용 하여 그 특성을 분석하였다. 첫째, Cu2S 나노 입자를 이용하여 양자점 감응형 태양전지의 상대 전극을 제조하였다. 표면 처리된 Cu2S나노입자 소재 상대전극은 산화 환원 쌍에 대한 촉매 활성을 향상시켜 염료감응 태양전지의 효율을 향상시킨다. 둘째, 열처리 된 저비용 친환경CZTS(Cu2ZnSnS4) 나노 입자 상대 전극을 이용하여 염료 감응형 태양전지의 효율을 향상시켰다. 셋째, 하이브리드 금속-Cu2S 나노 결정을 새로운 방법으로 합성하였다. 금속-Cu2S 나노입자는 광촉매 수소 생성에서 TiO2에 대한 효과적인 조촉매로서 적용되어 수소발생효율을 향상시켰다 마지막으로, 광촉매 수소 생산을 위한 새롭고 쉬운 용액공정 합성 방법에 기반한 TiO2-CuSbS2 (CAS) 복합체를 개발하여 수소발생효율을 향상시켰다.

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목차

1. Introduction 2--
1.1. Nanomaterials 2--
1.1.1. General characteristics of nanomaterials 2--
1.1.2. Synthesis of nanomaterials 3--
1.1.3. Solution processed colloidal nanocrystals 5--
1.2. Application of nanomaterials 8--
1.2.1. Solar energy conversion devices of nanomaterials 9--
1.2.2. Nanomaterials in solar cells 11--
1.2.3. Hydrogen generation using nanomaterials 10--
1.3. Dye-sensitized solar cell (DSSC) 12--
1.3.1. Principle of DSSC 12--
1.3.2. Counter electrode of DSSC 13--
1.4. Quantum dot-sensitized solar cell (QDSSC) 14--
1.4.1. Principle of QDSSC 14--
1.4.2. Counter electrode of QDSSC 16--
1.5. Photocatalytic hydrogen generation 18--
1.5.1. Principle of photocatalytic hydrogen generation 19--
1.5.2. Photocatalytic hydrogen generation by water decomposition 19--
1.6. Reference 22--

2. Improvement of CdSe quantum dot-sensitized solar cells by surface modification of Cu2S nanocrystals counter electrode 27--
2.1. Introduction 29--
2.2. Experimental 31--
2.2.1. Materials 31--
2.2.2. Synthesis of CdS quantum dots 31--
2.2.3. Synthesis of Cu2S quantum dots 32--
2.2.4. Preparation of photoanode, electrolyte, and counter electrode 33--
2.2.5. Material Characterization 34--
2.2.6. Photoelectrochemical Characterization 35--
2.3. Result and discussion 36--
2.4. Conclusion 48--
2.5. Reference 49--

3. Enhanced catalytic activity of Cu2ZnSnS4 colloidal nanocrystals as counter electrode of high efficient dye-sensitized solar cells. 54--
3.1. Introduction 56--
3.2. Experimental 58--
3.2.1. Materials 58
3.2.2. Synthesis of CZTS nanocrystals 58--
3.2.3. Preparation of photo-anode and counter electrode 59--
3.2.4. Material characterization 60--
3.2.5. Photo-electrochemical characterization 60--
3.3. Result and discussion 61--
3.4. Conclusion 71--
3.5. Reference 73--

4. Hybrid metal-Cu2S nanostructures as efficient co-catalysts for photocatalytic hydrogen generation 77--
4.1. Introduction 79--
4.2. Experimental 81--
4.2.1. Materials 81--
4.2.2. Synthesis of Pt nanoparticles 81--
4.2.3. Synthesis of FePt nanoparticles 82--
4.2.4. Synthesis of Cu2S nanoparticles 82--
4.2.5. Synthesis of Metal-Cu2S hybrid nanoparticles 83--
4.2.6. Material Characterization 83--
4.2.7. Photocatalytic H2 production 83--
4.2.8. Electrochemical characterization 84--
4.3. Result and discussion 85--
4.4. Conclusion 96--
4.5. Reference 97--

5. A facile solution synthesis of CuSbS2/TiO2 composite for highly efficient photocatalytic hydrogen generation 100--
5.1. Introduction 102--
5.2. Experimental Procedures 104--
5.2.1. Materials 104--
5.2.2. Synthesis of CuSbS2 /TiO2 photocatalyst 105--
5.2.3. Material Characterization 105--
5.2.4. Photocatalytic hydrogen production 106--
5.2.5. Electrochemical characterization 107--
5.3. Result and discussion 108--
5.4. Conclusion 124--
5.5. Reference 126--
Summary (in Korean) 130--

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