Co/ZnO與PbX (X=Se,Te)奈米材料合成、特性分析與在太陽能電池上的應用

Abstract

本論文嘗試將Co/ZnO奈米柱和半導體PbX(X=Se, Te)奈米粒子應用在太陽能電池上。Co/ZnO奈米柱是以水熱法合成，並藉由添加不同比例的反應物cobalt nitrate來研究Co2+摻雜對Co/ZnO形貌的影響。在X光粉末繞射圖中Co/ZnO仍維持wurtzite結構，而掃描式電子顯微鏡影像顯示不同Co量的摻雜對其形貌有很大的影響。同時觀察高解析穿透式電子顯微鏡影像得知柱狀的生長方向。更進一步，X光吸收圖譜的測量證明Co的確取代了Zn的位置，且沒有其他Co的衍生物產生。根據上述實驗結果，提出一個合理機制來說明形貌變化的現象。接著測量UV-Vis吸收、磁光、光電流轉換效率和磁性，結果顯示本實驗所合成的Co/ZnO雖然不適合當作太陽能電池使用，但其擁有室溫鐵磁性質，是一具有潛力的稀磁半導體材料。 利用電化學沉積PbSe和PbTe奈米粒子在導電玻璃和TiO2薄膜表面。此合成方法簡單、迅速，而且能改善奈米粒子間和與TiO2的連結。使用電壓2~3伏特時可以沉積PbSe和PbTe奈米粒子。PbSe以奈米粒子或是方塊狀形貌生成，而PbTe粒子是以樹葉狀的形貌覆蓋在基板上。將樣品製作成簡易的太陽能電池，並以碘液為電解液做光電流量測，發現PbSe和PbTe會和碘液反應，只有在奈米粒子少量和短時間量測時能得到較佳的光電轉換效率。而更換Na2S溶液和離子液體當電解液時並沒有得到更好的效率。即使如此，依然顯示出PbSe和PbTe奈米粒子對於光電流轉換效率是有助益的。

In this thesis, we synthesized Co doped ZnO (Co/ZnO) nanorods and PbX (X=Se, Te) nanoparticles, which were used to fabricate solar cell. Co/ZnO nanorods was synthesized by hydrothermal method. A series of hydrothermal reactions were carried out to study the effect of Co2+ ions to the morphology of Co/ZnO nanocrystals. SEM/TEM images of Co/ZnO nanocrystals revealed the effect of initial concentration of Co2+ ion to crystal morphology. X-ray adsorption analysis indicated that the Co2+ ions are located in the tetrahedral sites of Co/ZnO host material. A mechanism to describe the crystal shape of as-synthesized Co/ZnO nanocrystals was proposed. UV-Vis and magneto-photoluminescence spectra, photocurrent measurement and SQUID were employed to study the effect of different Co2+ ion to physical properties of Co/ZnO nanomaterials. Electrochemical deposition was used to grow PbX (X = Se, Te) nanoparticles on the substrates of glass and TiO2 thin film. The particle size of PbX was controlled by the duration of deposition time. The morphology of PbSe exhibits irregular or cubic shape, whereas PbTe formed a unique leaf-shape crystals, depending on the reaction conditions. The as-prepared PbX/TiO2 films were used as electrodes for the semiconductor-sensitized solar cell. Three electrolyte solutions (I3-/I-, Na2S, ionic liquid) were used to evaluate the effect of electrolytes to the power conversion. For I3-/I- electrolyte, the as-fabricated solar cells exhibited low power conversion efficiency due to reaction between PbSe/PbTe nanoparticles and I3-/I- electrolyte. The Na2S solution and ionic liquid did not react with PbSe/PbTe but the power conversion efficiency were not improved as well.