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Investigation on Chalcogenides Sensitized Titanium Oxide Stereo-structural Photo-sensitive Cells
|Authors: ||Tzeng, Wei-Jei|
|Keywords: ||二氧化鈦奈米管陣列;陽極氧化法;ICLR;CuInS2;In2S3;drop casting|
titanium oxide nanotube arrays;anodic oxidation;ICLR;CuInS2;In2S3;drop casting
|Issue Date: ||2018-08-22T03:40:04Z
|Abstract: ||本研究利用簡易的電化學陽極氧化法製備二氧化鈦奈米管陣列TNAs立體結構，不需真空製程使用ICLR與drop coating方式披覆光敏材料硫族化物In2S3 (InS)，CuInS2(CIS)在TNAs立體結構中，形成量子點(QD)、奈米粒子(NP)到薄膜(TF)型式的光敏層；完成TNAs立體結構披鍍光敏層填充液態電解質之光電化學電池，進一步達成全固態的TNAs立體結構披鍍光敏層之光敏太陽能電池。 陽極氧化法使用極性有機電解液成功製備TNAs，經450C/30min的熱處理獲得純相銳鈦礦。光觸媒分解MB效率為80％。經過TNL修飾的TNAs (T-TNAs)光觸媒效率可提高到90％。當365nmUV光照射時，TNAs在5秒內迅速獲得峰值光電流，然後下降到一恆定值。T-TNAs光電流密度增加了約15％。365nm UV光對TNAs的有效照射深度約8m（1h陽極氧化）。為了得到可見光的光響應，SILAR方法在T-TNAs上披鍍CuInS2（CIS），較低前驅物濃度（0.01M）的CIS得到比高濃度（1M）披鍍者較高的光電流密度。峰值光電流沒有迅速變低是由於CIS高光電轉換率和快速電子轉移，減少電子-電洞對再結合。 利用ICLR方法在T-TNAs上披鍍CIS的薄膜是由小於20nm球形顆粒所組成，其中Cu:In不一定為CuSa和InSb沉積週期數的比。化學計量CuInS2可以通過控制前驅物濃度和ICLR過程中沉積循環次數得到。在100 mW/cm 2可見光照射下，可得到至少300A/cm2的高光電流密度，顯示無機CIS可取代有機染料用於太陽能電池。 奈米顆粒狀CIS容易沉積在TNAs頂部，製作鬆散排列型Ti/TNAs約1m長度，稱為類桿狀TNAs，400oC/30min熱處理得到最佳純相結晶。經由drop-casting披覆CIS，披覆CIS的TNAs可吸收可見光，其中以TNAs/CIS5得到最佳的光電流，透過加入In2S3緩衝層所製作的TNAs/InS3CIS5更進一步改善光電流。交流阻抗分析研究各界面間的電子傳輸機制，發現披鍍CIS可減少TNAs/電解液界面阻抗，In2S3緩衝層可更進一步改進TNAs/CIS電子傳輸。可見光照射下，5minTNAs/ CIS5少數載子壽命很短；而增加In2S3緩衝層的5minTNAs/InS3CIS5則可增加少數載子壽命，增加TNAs光敏特性。 TNA/CIS存在Cu擴散進入TiO2的問題？以旋轉塗佈方式填充固態In2S3和CuInS2在波浪型TiO2上。在TiO2/In2S3結構披鍍CuCl2(aq)和CIS，發現CuCl2(aq)的Cu嚴重擴散進入In2S3，但CIS中的Cu擴散則比較不明顯，因此In2S3/CIS界面可藉由Cu的擴散，減少In2S3/CIS界面晶格變化梯度，改善DC等效電路中的短路電阻Rsh，增進開路電壓Voc。在無In2S3緩衝層的TNAs/CIS10結構光敏效果差，隨InS次數增加，Voc隨之提升，InS15CIS10可得到0.56V開路電壓。製作無電解液的全固態立體光敏電池，得到5minTNAs/TiO2/InS10/CIS10 /Au量測到最佳光敏特性。|
The stereo-structures of titanium oxide nanotube arrays (TNAs) were synthesized by simple electrochemical anodic oxidation method. Photoseisitive chalcogenides In2S3 (InS) and CuInS2 (CIS) were deposited on/in the prepared stereo-structures of TNAs by ionic compounds lamination reaction (ICLR) and drop cating methods. The deposited photosensitive layers formed quantum dots (QD), nano-particles (NP) and thin films (TF). After various type of photosensitive layers deposition, the obtained photoanodes were emmersed in liquid electrolyte to form photoelectrochemical cells or the photoanodes coated by gold cathode to form full solid photosensitive solar cells. TNAs were successfully prepared by anodic oxidation using a polar organic electrolyte system. A pure anatase crystal phase was achieved after post-annealing at 450°C/30 min. The photocatalytic efficiency of 80% decomposition of MB was achieved for 60V/2h anodization. The titanium oxide nano-layer modified TNAs (T-TNAs) showed photocatalytic efficiency up to 90% of MB decomposition. When the TNAs were illuminated with 365 nm wavelength of UV light, the peak photocurrent was obtained rapidly within the first 5 s and then decreased to a constant value of photocurrent density. The photocurrent density of T-TNAs increased about 15%. The effective illumination depth of UV light of 365 nm was about 8 μm (1 h anodization) for a well-developed crystal lattice of TNAs. The lower concentration (0.01 M) of CIS achieved a higher photocurrent density than the higher concentration (1 M) of CIS did. The peak photocurrent did not decrease rapidly due to the efficient energy harvesting and fast electron transfer of CIS to reduce the electron-hole recombination. The CIS layers on the T-TNAs comprised nano-spherical particles less than 20 nm in size produced by the ICLR method. The number of deposition cycles of InSb is not necessarily equal to the number of deposition cycles of CuSa for stoichiometric CIS. Stoichiometric CuInS2 could be obtained approximately by controlling the precursor concentration and deposition cycles of the ICLR process. A high current density of at least 300A/cm2 could be achieved under visible light illumination intensity of 100 mW/cm2. The results indicated the inorganic CIS could be instead of organic dye using in photosensitive solar cells. The nucleation and growth of the CIS nanoparticles proceeded along the edge of the top open hole of the nanotubes forming a crater-like shape, and then extended over the tubes surface. Spatially ordered and vertically free-standing TNAs were prepared by a two-step anodization process. Such rod-like TNAs were annealed at 400 C for 30 min, yielding pure anatase phase. Through a novel drop-casting process, CIS nanoparticles were coated on the top surfaces, walls, and bottom of the nanotubes in the rod-like TNAs. The five-cyclic drop-cast layer, CIS5, showed suitable photosensitizer coverage of the TNAs, effectively generating photoelectrons that could uniformly travel into the TNAs. The AC impedance analyses (EIS) were used to determine the interface charge transfer impedance of the bare TNAs, TNA/CIS5, and TNA/InS3CIS5 in electrolyte. The photosensitized electrons transferred from the photoabsorption CIS layer to the TNAs. The buffer layer of In2S3 in TNA/InS3CIS5 improved electrons transferring from the photoabsorption CIS layer to the TNAs more efficiently. The potential relaxation experiments gave us information on the kinetics of electron recombination in TNA/ InS3CIS5 nanostructure, indicating a longer lifetime of photoinduced electrons in the chalcogenide photosensitized TNAs. The Cu composition could diffuse into TiO2 in the TNA/CIS photoanode. The In2S3 and CuInS2 films were deposited on wave-like TiO2 by spin coating method to investigate the interdiffusion. When CuCl2(aq) deposited on TiO2/In2S3 structure, it was found the Cu diffusion into In2S3 seriously. However, while CIS deposition on TiO2/In2S3 structure, it was found the Cu diffusion into In2S3 not obviously. Thus, control the diffusion of Cu between the interface of In2S3 and CIS could decrease the gradient of lattice change to improve short circuit resistance of Rsh in the DC equivalent circuit and increased open circuit voltage Voc. The low photosensitivity of TNAs/CIS10 could be improved by adding InS buffer layer to increase Voc. The TNAs/InS10CIS10 could obtain 0.56V of Voc. The full solid-state stereo-structural 5minTNAs/TiO2/InS10/CIS10/Au cell exhibited well photosensitivity under visible light illumination.
|Appears in Collections:||[輪機工程學系] 博碩士論文|
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