阻抗分析應用在染料敏化太陽能電池與 鈣鈦礦太陽能電池之研究

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Title:	阻抗分析應用在染料敏化太陽能電池與鈣鈦礦太陽能電池之研究
Other Titles:	Dye Sensitized Solar Cells and Perovskite Solar Cells studied by Impedance Spectroscopy
Authors:	林冠佑 LIN, GUAN-YOU
Contributors:	簡世森 CHIEN, FOREST SHIH-SEN 應用物理學系
Keywords:	染料敏化太陽能電池;白金;碳膠;熱處理;效率;鈣鈦礦太陽能電池;阻抗 dye-sensitized solar cells (DSCs);Pt;carbon paste (CP);sintering;perovskite solar cells;impedance spectroscopy
Date:	2018
Issue Date:	2019-01-10T09:14:22Z (UTC)
Abstract:	染料敏化太陽能電池(Dye Sensitized Solar Cells，DSCs)具有低成本、高產量的優勢，目前相當地受到矚目，是很有發展潛力的太陽能電池。基於白金(Platinum, Pt)優良的催化能力，對電極大部份即由Pt所組成。但是，Pt為稀有金屬之一，價格也是目前最昂貴的金屬，若要達成普及大面積製作將會提高其製作成本。現今已找到替代材料當作DSCs的對電極，主要被廣泛應用的材料為碳基材料。本研究利用碳膠(CP)取代Pt做為DSCs的對電極，並且對其進行不同溫度的熱處理，觀察其對DSCs效能變化的影響。實驗結果得知，當熱處理溫度為300 ℃時，電池的總轉換效率可以達到4.9 ％，這與具有Pt對電極的電池的5.7 ％相當。熱處理後，CP的結晶質量得到改善，導致電池串聯電阻降低，CP功函數增加。我們還發現，由於CP的表面積增加和電解液中三碘化物的還原電位與CP的功函數之間的能量匹配，電解液中三碘化物的還原速率顯著提高。成功地將熱處理後的CP應用在DSCs的對電極上，達到100 %取代傳統Pt對電極的目的。另外，由於鈣鈦礦具有可調整能隙值、極高的吸收係數、低非輻射載子複合率等優點，因此在近年裡，有許多研究學者將其應用於太陽能電池的吸光層當中。本研究使用以CH3NH3PbI3作為光吸收材料的鈣鈦礦太陽能電池。於水氧值低的手套箱中，使用阻抗頻譜來觀察405 nm、532 nm與650 nm的雷射與不同光功率密度對鈣鈦礦太陽能電池的影響。目前得知，阻抗頻譜中高頻處的曲線與鈣鈦礦主動層的行為有關，而阻抗頻譜中低頻處的曲線則與鈣鈦礦主動層與二氧化鈦層間的電子電洞對再結合有關。實驗結果可以發現，不論是鈣鈦礦主動層的電阻(Rp)或是鈣鈦礦主動層與二氧化鈦層間的電子電洞對再結合電阻(Rrec)的倒數，都與光功率密度成正相關。而CH3NH3PbI3鈣鈦礦中的吸收躍遷對於光生電荷的提取至關重要，這會影響鈣鈦礦太陽能電池的光伏性能。實驗上觀察到鈣鈦礦層對532 nm激發表現出高的光電導響應。這是由於532 nm將電子激發到高導帶，並且在該導帶處的短電子收集時間導致對532 nm照射的高光電導響應。 Photoelectrochemical dye-sensitized solar cells (DSCs) have attracted much interest in the field of sustainable green energy. However, their counter electrodes (CEs) usually fabricated by the noble metal Pt. To obtain the alternative Pt-Free CEs for DSCs is desirable for the wide deployment of DSCs. Alternative materials have been found as counter electrodes for DSCs, and the most widely used materials are carbon-based materials. In this study, carbon paste (CP) was used to replace Pt as the CEs of DSCs, and it was subjected to calcination at different thermal treatment temperatures to observe its effect on the performance of DSCs.The experimental results showed that when the thermal treatment temperature was 300 ℃, the overall conversion efficiency of cells can reach 4.9%, which is comparable to 5.7% of the cells with counter electrode of platinum. After thermal treatment, crystalline quality of CP was improved, resulting in the decrease of series resistance of cells and the increase of the work function of CP. We also showed that the reduction rate of triiodide is significantly enhanced due to the increase of surface area of CP and the energy matching between the reduction potential of triiodide and the work function of CP.Due to own the tunable band gap, high absorption coefficient, low non-radiation carrier recombination, perovskite materials received significant attention by many researchers in recent. There are many researchers used perovskite materials as light-harvesting materials for solar cells. This research cooperates with the Department of Chemical and Materials Engineering of Chang Gung University to provide a perovskite solar cells with CH3NH3PbI3 as light-harvesting material.In this study, perovskite solar cells were measured inside the glove box under low humidity and oxygen content. The impedance spectroscopy is used to observe the effects of different laser wavelengths and different laser power densities on perovskite solar cells. The first arc at higher frequencies is related to the perovskite layer, the second arc at lower frequencies is due to the recombination between the perovskite and TiO2 layer. The experimental results showed that whether Rp and Rrec decrease with the increase of the laser power density. In addition, because 532 nm excite electrons to the high conduction band, and the short electron extraction time at this conduction band results in the high photoconductance response to 532 nm illumination.
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