氮化銦染料敏化太陽能電池的應用

Abstract

研究的主題為氮化銦奈米顆粒在染料敏化太陽能電池上的應用。第一部分為氮化銦奈米顆粒經氣態沉積在二氧化鈦奈米薄膜的物理性質研究。第二部分為將InN/TiO2樣品封裝成染料敏化太陽能電池並研究氮化銦奈米顆粒對整體電池光電轉換效率的改變。第一部份:我們在厚度約3 μm的二氧化鈦奈米薄膜表面經由有機金屬化學氣象沉積的方式（Organo-metallic Chemical Vapor Deposition）來沉積氮化銦奈米顆粒，沉積溫度控制在573~723 K，沉積時間則是2~180 min。從SEM、XPS、XRD等圖譜的分析我們可以確定氮化銦的結晶性良好並且不會有氧化銦的干擾，但由於氮化銦的反應來自氣態樣品的三甲基銦與疊氮酸，因此整體上氮化銦粒子只能吸附在二氧化鈦的淺層（小於1 μm）。 第二主題部份我們探討N3與InN/TiO2系統的反應，首先在吸收光譜的測量上，我們發現N3吸收峰在氮化銦的影響下會有明顯的紅位移，這顯示氮化銦有可能與N3分子形成強烈鍵結，要在更進一步的研究N3分子與InN/TiO2基材的作用，我們以VASP理論計算來比較甲酸/甲酸自由基與苯甲酸/苯甲酸自由基和InN/TiO2系統的吸附能，結果顯示雖然甲酸分子氮化銦的吸附能會比對二氧化鈦減少50 %但相對的甲酸自由基對氮化銦的吸附能會比對二氧化鈦的吸附能高出2.5倍，在苯甲酸的系統也有相同的結果，苯甲酸自由基對的InN/TiO2吸附能高出苯甲酸甚多，這結果可以確定N3分子會以R’C(O)O•經由雙偶合架橋基（bidentate bridging）的形式與氮化銦形成穩定的鍵結。接著我們將厚度5-8.5 μm的二氧化鈦試片封裝成N3-DSSC，在IPCE與光電轉換效率的測量結果之中可以看到氮化銦粒子的沉積可以有效地增加N3-DSSC達13~20 %。在8.5 μm厚的二氧化鈦樣品上，在573 K沉積10 min的氮化銦，配合N3染料封裝成的太陽能電池效率最高可達到7.1 %。

The thesis is divided into two sections. The first section is the characterization of InN nanoparticles (NP) deposited on the surface of nanoporous TiO2 thin films. The second section is the application of the InN/TiO2 substrate for DSSC operation. In the first section, the InN NPs deposition over a 3μm thick TiO2 substrate was carried out in a homemade OMCVD system with the reaction of HN3 and (CH3)3In. The deposition time was controlled in the time range of 2~180 min at 573~723 K. SEM、 XPS and XRD analyses ensure high quality crystallinity InN was obtained. The InN NPs were noted to grow only on top surface layer of TiO2 substrate through the gas phase reaction. In the second section, we investigated InN enhancment effect on DSSC by immersing an InN/TiO2 substrate into N3 dye solution. The N3 absorption peak of the InN/TiO2-N3 substrate was red-shifted with respect to untreated TiO2-N3 indicating a strong interaction between InN NPs and the N3 molecule. To further study the interaction between N3 anchoring group (R’COOH) and the InN/TiO2 substrate, performed VASP theoretical calculations to model the adsorption of N3 on the InN/TiO2 substrate. To simplify the calculation, HCOOH/HC(O)O• and C6H5COOH/C6H5C(O)O• molecules were used as the carboxylic anchoring groups. Although the adsorption energies of HCOOH on top of the various layers of InN were found to decrease by 50 %, the binding energies of HC(O)O• bidentate bridging adsorption on two In atoms of different layers of InN were found to be very high. Similar results were also observed in benzoic acid system. These results suggest that the N3 dye can adsorb strongly on InN of the InN/TiO2 substrate through its anchoring R’C(O)O• group. We then modified InN/TiO2 substrates for DSSC applications. By varying TiO2 substrate thickness, InN/TiO2 DSSC showed 13~20 % enhancement in photovoltaic efficiency with respect to TiO2 DSSC, suggesting a new possible application of InN for the DSSC system. In the InN/TiO2 DSSC, the highest efficiency of 7.1 % had been achieved by using the 8.5 μm thick TiO2 substrate with 10 min InN deposition at 573 K.