以溶液製程製作高效率鈣鈦礦太陽能電池及結合透明電極之研究

Abstract

本篇論文第一部份探討以快速結晶(Drop-Casting)的溶液製程製作正規結構鈣鈦礦太陽能電池之優化過程。我們將元件從電子傳輸層緻密TiO2、主動層Perovskite、電洞傳輸層Spiro以及上電極，依序優化。在優化電子傳輸層的部分，我們探討元件在不同厚度及不同層數之TiO2下的表現，而在優化主動層Perovskite層的部分，分別測試了Perovskite的厚度、後退火溫度、後退火時間這三個條件，研究過程中我們觀察不同變因對於Perovskite成膜的影響，也以SEM及XRD來觀測Perovskite的結晶顆粒，分析Perovskite結晶的型態及完整度。最後在Spiro層以及上電極金的厚度優化完成後，我們製作出填充係數72、轉換效率15.7%的正規結構元件。 在第二部分的研究中，我們以介面改質材料HBC-6ImBr(HBC)來對石墨烯下電極表面進行親疏水性的改變，製作出以石墨烯為陽極的倒置鈣鈦礦太陽能電池。本章節中我們探討不同層數的石墨烯作為下電極的效果，以及不同層數HBC-6ImBr對於元件的影響，我們發現隨著石墨烯堆疊層數增加，石墨烯破洞減少，有利於作為下電極材料。而隨著HBC層數的增加，元件的填充係數逐漸上升，但因為HBC本身的電阻也會阻礙元件的光電流，我們測試出最優化的元件是以三層HBC作為介面改質來連接之後的材料，製作出轉換效率7.1%，填充係數52.4的石墨烯下電極元件。最後我們以奈米銀線取代倒置鈣鈦礦太陽能電池的上電極銀，以適當的後退火溫度，製作出半透明元件。

In the first part of this thesis, the optimized performance of Perovskite solar cells in conventional structure using drop-casting solution process has been achieved. Devices performance were sequentially improved by several testing, including thickness and the layer number of titanium dioxide (TiO2) which is used as electron transporting layer (ETL), annealing time, annealing temperature and thickness of Perovskite which is used as light absorption layer, thickness of hole transport layer (HTL) of N2,N2,N2′,N2′,N7,N7,N7′,N7′-octakis(4-methoxyphenyl)-9,9′-spirobi [9H-fluorene] -2,2′,7,7′-tetramine (Spiro-MeOTAD) and anode(Au) .The mechanisms behind for each part have been discussed as well. Via the measurement of Scanning electron microscopy(SEM) and X-ray diffraction(XRD),it proves that the drop-casting process is beneficial for crystallization of Perovskite. Finally the power conversion efficiency of the Perovskite solar cells in this study has achieved over 15.7%, with a filling factor (F.F) of 72%. In the second part, we successfully fabricate inverted perovskite solar cells using graphene as bottom anode. In order to convert graphene’s hydrophobic nature into hydrophilic, we insert a buffer material called HBC-6ImBr (Hexa-peri- hexabenzocoronene-6ImBr) between graphene and HTL. Besides, we find that cracks of graphene can be covered by stacking multilayer of graphene and effectively improve the device performance such as shunt resistance. Our best cell with tri-layer HBC-6ImBr and tri-layer graphene has reached 7.1% of power conversion efficiency and a fill factor of around 52%. At last, we try to replace Ag with sliver nano-wire (Ag-NW) to fabricate transparent devices in inverted structure with appropriate annealing temperature.