以原子層沉積技術低溫沉積復合阻絕層於二氧化鈦奈米管陣列之高效率、長時間穩定性軟性染料敏化太陽能電池之製作

Abstract

為降低地表太陽能發電的成本，新型的太陽能電池的發展除達到高能源轉換效率，電池材料成本、製程成本也需進一步降低。在各種新型態的太陽能電池中，染料敏化太陽能電池同時具有低成本與10%以上的高能源轉換效率，然而染敏電池結構中一般需使用液態的電解液做為電洞的傳導介質，長時間使用時由於電解液漏液十分不利電池的穩定性，不過最近在新型固態電洞傳輸材料的突破，全固態染敏電池達到接近10%的轉換效率，此一進展大幅提高了染敏電池的實用性，為進一步克服傳統二氧化鈦奈米粒子堆疊光陽極結構上固態材料的填充問題，我們提出利用陽極氧化法製備轉移到透明基板上之二氧化鈦奈米管陣列做為光陽極，由於奈米管所具有的長直孔隙，將十分有利於固態材料的填充。 然而在固態染敏電池的結構中，需完全阻絕電洞傳輸材料與透明導電層直接接觸，在傳統結構下一般先在透明導電層上沉積二氧化鈦緻密層，然而軟性材料無法承受結晶緻密層所需的熱製程，因此我們將使用原子層沉積法在二氧化鈦奈米管陣列內直接沉積阻絕層，此一做法將能夠較低的溫度下完成阻絕層的沉積並且不造成額外的電阻，因此同樣可應用在軟性基板上，將可望完成同時具有軟性、穩定性與高效率之全固態染敏電池。

To promote the terrestrial applications of solar energy harvesting, the evolving photovoltaic technologies focus on achieving higher energy conversion efficiency using novel device architectures by low cost materials. Dye-sensitized solar cell (DSSC), as a low cost type solar cell, has achieved over 10% power conversion efficiency. However, because of the liquid electrolyte used in conventional dye solar cells, problems on long term stability of DSSCs are easily induced by the leakage of the electrolyte. Recently, progress on hole transport materials (HTM) has almost solved this problem. Approximately 10% power conversion efficiency has also been achieved for full solid-state DSSCs (ssDSSC). In order to further improve the performance of the ssDSSC, the deposition of the HTM becomes a critical issue. Because for conventional DSSC with nanoparticle photoelectrode the small pore size among the nanoparticles heavily limited the possible infiltration depth of the HTM. To facilitate the deposition of the HTM, we propose utilizing anodized TiO2 nanotube-array to replace the nanoparticles in ssDSSC. The infiltration of the HTM within the straight and large pore of the nanotubes should be easy, and an increased active thickness can be expected. In this project, a barrier layer is proposed to be deposited by atomic layer deposition (ALD) method for nanotube photoelectrode instead of the direct sputtering or spray pyrolysis TiO2 condense layer used in conventional nanoparticle ssDSSC, There are many advantages for this new method. First, because TiO2 can be deposited at low temperature by ALD, similar method can be applied to thermal unsustainable substrate as plastic sheet as well. Also, the additionally deposited TiO2 barrier layer will not induce additional transport resistance for charge collection; it only blocks the recombination paths between conductive oxide and the HTM. A highly efficient, long-term stable and even flexible full solid-state dye-sensitized solar cell is expected to be fabricated.