應用於染料敏化太陽能電池氧化錫奈米花與鋰摻雜氧化鋅光電極複合材料的合成與電化學性能

Synthesis and Electrochemical Performance of Composite SnO2 Nanoflower with Li Doped ZnO Photoanodes in Dye-Sensitized Solar Cells

雷朋(Ripon Bhattacharjee)

指導教授 ： 洪逸明

元智大學/工程學院/化學工程與材料科學學系/碩士(2013年)

https://doi.org/10.6838/YZU.2013.00035

摘要

在本研究中，係以SnO2作為基材，快速的製備染料敏化太陽能電池。本研究成功地以水熱法，在200 oC下熱處理48小時，製備出長度為700 nm，直徑1.5μm的SnO2奈米花粉末。而商業化的SnO2奈米粉末則與不同比例的SNF混合，合成SnO2奈米複合光陽極。以鋰摻雜的ZnO（LZO）奈米顆粒，其直徑為800 nm，透過水解縮合的方法製備，並用它作為光陽極SNC（SN-Z）的表面絕緣層。
成功製備的SNF利用掃描式電子顯微鏡，X光繞射圖譜及穿透式電子顯微鏡來觀察其特徵。通過在黑暗和照射條件下來測SnO2奈米結構和SN-Z光陽極的光電性能。在染料敏化太陽能電池里，用開路電壓衰減和暗電流技術來分析電子壽命與複合過程。用電化學阻抗譜來分析SNC和SN-Z光陽極的電化學性能。
掃描隧道顯微圖像展示了SNC奈米結構被LZO奈米顆粒完全覆蓋，SNP很成功地填充了SNF奈米棒之間的間隙，多餘的SNP提高了導電玻璃與SNF之間的結合力，使暴露出的導電玻璃面積變得最小。1:1 wt. %的SNC表現出了525mV的開路電壓和0.7%的轉換效率。用LZO作為絕緣層之後，SN-Z的填充因子和開路電壓提高了接近1.5倍。SN-Z (1:1)作為光陽極的電池表現出了最高的轉換效率，其值為4.73mA cm-2以及填充因子為69.33，此數值比其他SNC和SN-Z作為光陽極電池的轉換效率都要高。開路電壓衰減和暗電流顯示SN-Z (1:0.5)具有更長的電子壽命，這表明其最高的光電轉換效率（80.6%），以及更高的開路電壓（670mV），數值要比其他光陽極的電池高。SNC與LZO能隙的不同通過減小內電阻來提高電子轉移過程，這可以從電化學阻抗譜里得到證實。
漏電子的壓制，結合力的提高以及LZO層對染料吸收量的增加，提高了電池的轉換效率，這個研究表明了不同能隙半導體表面的重要性是準備高效率染料敏化電池的合理選擇。

關鍵字

氧化錫納米花 ； 暗電流 ； 開路電壓衰減 ； 染料敏化太陽能電池

並列摘要

In this work, dye sensitized solar cells (DSSCs) based on SnO2 nanoflowers (SNF) are fabricated for the fast time. SnO2 nanoflowers (SNF) with 700 nm length and 1.5 μm in diameters were successfully prepared at 200 oC for 48 h by a hydrothermal method. Commercial SnO2 nanoparticles (SNP) were mixed with different amount of SNF to prepare SnO2 nanocomposite photoanode (SNC). Aggregated Li doped ZnO (LZO) nanoparticles of 800 nm in diameter are prepared by hydrolysis condensation method and used it as insulating layer at the top surface of SNC photoanode (SN-Z).
The as synthesized SNF are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM). The photovoltaic performance of SnO2 nanostructure and SN-Z photoanode are carried out by measuring the J-V curves both in dark and under illumination. Open circuit voltage decay (OCVD) and dark current techniques are used to analysis the lifetime and recombination process in a DSSC. Electrochemical impedance spectroscopy (EIS) is used to investigate the electrochemical properties of SNC and SN-Z photoanode DSSCs.
SEM micrographs show SNC nanostructures are completely covered by the LZO nanoparticle and SNP successfully fill the gap between the nanorods of SNF, more over SNP, improved the interconnection between the FTO and SNF, and minimized the exposed site of FTO. 1:1 wt. % of SNC exhibited a high efficiency of 0.7 % with 525 mV of open circuit voltage (Voc). After using LZO as an insulating layer, FF and Voc of SN-Z photoanode DSSCs are improved almost 1.5 fold. Highest Jsc and FF of 4.73 mA cm-2 and 69.33 % for SN-Z (1:1) photoanode DSSC achieved higher efficiency than other SNC and SN-Z photoanode DSSCs. Longer lifetime is observed from OCVD and dark current of SN-Z (1:0.5) photoanode DSSC shows the highest incident photon to charge conversion efficiency (IPCE) of 80.6% with higher Voc of 670 mV than other photoanode DSSCs. Different band gap of SNC and LZO improved the electron transfer process by reducing the internal resistances which are proved from EIS.
Suppression of electron leakage, improved interconnections and increased dye adsorption amount by the LZO layer on SNC enhanced the DSSC efficiency. This study implies the importance of different band gap semiconductor interface can be a suitable option for preparing a high efficiency DSSC.

並列關鍵字

SnO2 Nanoflower ； Dark current ； OCVD ； Dye sensitized solar cells.

參考文獻

[3] Baxter J. B. "Commercialization of Dye Sensitized Solar Cells: Present Status and Future Research Needs to Improve Efficiency, Stability, and Manufacturing". Journal of Vacuum Science & Technology A. 30 (2012) 020801-020819.

[4] Desilvestro H. 4th International Conference on the Industrialisation of DSC. Colorado Springs, Colorado (USA)2010.

[6] Hashmi K., Miettunen T., Peltola J., Halme I., Asghar K., Aitola M., Toivola P., Lund G. "Review of Materials and Manufacturing Options for Large Area Flexible Dye Solar Cells, Renewable Sustainable Energy". 15.

[7] Yella A., Lee H. W., Tsao H. N., Yi C., Chandiran A. K., Nazeeruddin M. K., Diau E. W., Yeh C. Y., Zakeeruddin S. M., Gratzel M. "Porphyrin-Sensitized Solar Cells with Cobalt (II/III)-Based Redox Electrolyte Exceed 12 Percent Efficiency". Science. 334 (2011) 629-634.

[8] Chiba A., Islam Y., Komiya R., Koide N., Han L. Y. " Dye-Sensitized Solar Cells with Conversion Efficiency of 11.1%". J Appl Phys Part 2 Lett Express. 45 (2006) 638-640.