成長高品質石墨烯並應用於有機-無機混合型太陽能電池

Abstract

在本論文中，我們使用管狀的銅箔成功的成長出高品質單晶的石墨烯，而為了使後續在應用方面可以更加方便與保持石墨烯的完整性，我們也進一步優化並改良成長的參數，使用石墨塊當擋塊來使氣體在管內的碰撞機率增高，可得到高品質的石墨烯但相當不均勻，另外，我們也對銅箔表面的氧化層做處理，成長出來的石墨烯晶粒大小可達數十微米，最後我們改變成長時間及通入的氣體流量，我們選用小流量長時間的成長參數成功的成長出高品質且高均勻度，拉曼訊號2D/G比值為3的石墨烯。 另外，我們將成長出來高品質的石墨烯運用PET膜的輔助，製作成透明導電薄膜。而經由模擬我們可以得知，PEDOT：PSS其橫向傳導很差，所以，我們使用石墨烯透明導電薄膜來幫助PEDOT收集並傳導載子。在矽基板混合型太陽能電池上，我們使用兩層的石墨烯透明導電膜可使其光電轉換效率達到8.95%，其提升幅度為53.5%。而在砷化鎵基混合式太陽能電池上，我們使用單層石墨烯透明導電薄膜，其光電轉換效率從6.85%提升至8.60%，提升幅度為25.5%。

In this thesis, we successfully use tubular copper foil to grow high-quality single-crystalline graphene. In order to scale up for device applications, we have further optimized and improved the growth parameters. First, we use graphite as blockers to increase the probability of gas collisions on to the copper foil. We obtain high-quality graphene but the uniformity is not as ideal. Next, we prepare an oxide layer on the copper foil with surface cleaning techniques, which successfully increase the grain size of graphene to about tens of microns. Finally, we change the growth time and gas flow rate, where low rate and long growth time result in high-quality graphene of which the ratio of Raman signal 2D/G peak is 3 with very good uniformity. Moreover, we transfer this high-quality graphene onto a PET film as the transparent conductive electrode for hybrid organic-inorganic solar cells. According to the simulation, we can see that later carrier conduction of PEDOT:PSS is limited by the doping concentration as well as the conductivity. Therefore, we have employed graphene transparent conductive film to help collect and transport carriers. In the silicon base hybrid solar cells, the two-layer-graphene transparent conductive film give rise to the best device performance. The power conversion efficiency of device is 8.95 %, corresponding to an enhancement factor of 53.5%. In the GaAs base hybrid solar cells, we use single-layer- graphene transparent conductive film to optimize the cells. The power conversion efficiency of device is 8.60 %, corresponding to enhancement of 25.5%.