改變TiO2結構對(CH3NH3)PbI3敏化太陽能電池特性影響之研究

Abstract

本論文研究主題是探討二氧化鈦奈米結構對(CH3NH3)PbI3鈣鈦礦敏化太陽能電池之影響性。 在第一部份的實驗中，將一維結構的二氧化鈦奈米管陣列應用於(CH3NH3)PbI3鈣鈦礦敏化太陽能電池作為光電極，奈米管的一維陣列排序結構能克服奈米粒因不規則排列結構而受限於電子擴散長度問題，使電子傳遞速度快並提升光電流密度。實驗中我們可以得知當奈米管長度為5μm時在乙酸乙酯，0.9M碘化鋰，0.45M碘，0.05M尿素電解液系統下可得到較好的(CH3NH3)PbI3敏化太陽能電池電性，當電解液含足夠碘離子時，可較有效地還原氧化的敏化材料。 當二氧化鈦奈米管進行不同後處理時，(CH3NH3)PbI3鈣鈦礦在奈米管上的吸附量及電解液在奈米管間孔洞的滲透性均有所改變，經過TiCl4處理增加表面面積的二氧化鈦奈米管可吸附最多的(CH3NH3)PbI3，而經過鹽酸處理後的二氧化鈦奈米管提升了電解液的滲透性而可獲得最高的光電流密度。 為了解決(CH3NH3)PbI3在照光條件下會漸漸的被氧化還原電解液溶解反應而導致電池壽命期短的問題，研究應用固態的電洞傳輸層取代電解液。在全固態光電池結構下，光電極薄膜厚度過薄會使得敏化材料吸附量低，過厚則會因電子擴散長度限制，兩者皆導致電池元件特性降低；當電洞傳輸層添加LiTFSI可提升電洞遷移率及導電性增加，但也導致載子復合時間減短而使開路電壓呈明顯下降。使用65 °C下加熱合成的二氧化鈦溶膠做為光電極，再沉積30 wt%的(CH3NH3)PbI3並以PTAA做為電洞傳輸層的固態電池結構可獲得較好的效率。

In this thesis, we studied the influence of titanium dioxide (TiO2) nanostructure on organo-lead-halide (CH3NH3)PbI3 perovskite sensitized solar cell. With a thin light absorbing film in perovskite sensitized solar cell, the nanostructured host material can be important for harvesting light for high efficiency. In the first part of the thesis, one-dimensional (1D) TiO2 nanotube-array has been applied to (CH3NH3)PbI3 perovskite sensitized solar cell. One-dimensional nanotube-array provide a direct path for the photogenerated electron transport. With an appropriate nanotube length of 5μm in the redox electrolyte of 0.9M LiI, 0.45M I2, 0.05M urea in ethyl acetate, (CH3NH3)PbI3 perovskite can be more efficiently reduced in the solar cell due to high concentration of iodine. Different post-processing of the nanotubes have been investigated to increase the amount of the (CH3NH3)PbI3 perovskite absorbed on the nanotubes or improve infiltration of electrolyte into voids of the nanotubes. On TiCl4 treated TiO2 nanotubes, the adsorption of the (CH3NH3)PbI3 have increased the most because of enlarged surface area of the nanotubes. TiO2 nanotubes subjected to HCl treatment have the highest short-circuit photocurrent density because of improved infiltration of electrolyte in void. Due to the fact that (CH3NH3)PbI3 tends to be dissolved gradually in the redox electrolyte, we have studied using solid-state hole transport material to replace the redox electrolyte; With the TiO2 thickness less than 200nm, the lowering in performance with decreased thickness of the TiO2 film is likely due to the decreased amount of the adsorbed perovskite. If TiO2 film thickness is too thick, over 1μm the performance would be restricted by electron diffusion length. Adding LiTFSI to the hole transport material PTAA not only increases hole mobility but also decreases carrier lifetime, which induces lowering in open-circuit voltage. For 65 °C synthesized TiO2 nanoparticle photoanode, depositing 30 wt% (CH3NH3)PbI3 on photoanode with PTAA as hole transport material, the full solid-state solar cell exhibited better performance.