雙層結構硒膜應用於銅銦鎵硒吸收層之兩階段硒化研究

Abstract

本論文利用大氣電漿輔助化學氣相沉積法去成長不同結晶性硒膜於銅鎵銦金屬前驅層上，並利用兩階段快速高溫製程進行硒化，將原來硒/銦/銅鎵的前驅層化合成黃銅礦結構的銅銦鎵硒薄膜並進行薄膜分析，最後完成銅銦鎵硒薄膜太陽能電池。大氣電漿輔助化學相沉積是屬於非真空系統，且有似濺鍍技術的大面積鍍膜能力，硒的原料使用率相較於硒蒸鍍系統有較好的表現。 初步研究著重於不同的基板溫度對於硒膜表面形貌、薄膜連續性、結晶程度與電池效率的影響。再進一步研究結晶硒與非晶硒以不同比例堆疊對於太陽能電池電性(效率、漏電流等)上之影響，我們預期結合非晶硒成長銅銦鎵硒結晶性較佳與結晶硒可與鉬背電極形成比較好的歐姆接觸之優點，進而改善銅銦鎵硒太陽能電池的效率。 太陽能電池其結構為銀指狀電極/氧化銦鍚/氧化鋅/硫化鎘/銅銦鎵硒/鉬背電極/鈉玻璃，元件有效面積為0.38平方公分並利用太陽光模擬系統量測元件效率、開路電壓、短路電流與填充因子等參數。研究結果指出雙層結構硒膜 (基板溫度125oC且電漿輔助成長的結晶硒膜與基板溫度45oC且無電漿輔助成長的非晶硒膜之比例為1:1) 與金屬前驅層所硒化並製作完成的銅銦鎵硒薄膜具有最佳的品質，以此方法製作完成的太陽能電池元件轉換效率可以達到8.68%，填充因子為58.1、開路電壓0.47V、短路電流31.4mA/cm2. 我們成功利用大氣電漿輔助化學氣相沉積法沉積不同比例與結晶性的硒膜於金屬前驅層，然後利用兩階段快速高溫製程形成銅銦鎵硒薄膜，最後製成太陽能電池。

Various crystallinity Selenium thin films were deposited by atmospheric plasma enhanced chemical vapor deposition on In/Cu3Ga precursor layer. Then, selenium-coated metal precursor were formed CIGS absorber layers using rapid thermal processing (RTP). Finally, CIGS solar cells were fabricated and measured. The atmospheric pressure plasma enhanced chemical vapor deposition (APPECVD) is a non-vacuum system and has similar large scale deposition ability of sputtering technique. Selenium deposited by the APPECVD has better selenium utilization ratio than thermal evaporator in vacuum. For preliminary research, we study surface roughness, film continuity and crystallinity of selenium thin films deposited at 45, 85, 125oC and w/o plasma enhancement, and their influence on performance of CIGS solar cells. For further research, we employed advantages of amorphous selenium (Fast growth rate and better CIGS crystallinity) and hexagonal selenium (forming better quality of MoSe2 and reducing series resistance) and used stacked a-Se/h-Se films to improve the CIGS solar cell efficiency. Based on the result, the best ratio of a-Se and h-Se is 1:1. The structure of CIGS solar cell is Ag finger electrode/ITO/i-ZnO/CdS/CIGS/Mo back electrode/sodium lime glass. Using bilayer a-Se/h-Se films can form better quality CIGS absorber layers to obtain best solar cell performance: The active-area efficiency is 8.68% at cell size of 0.38 cm2, fill factor of 58.1 %, open circuit voltage of 0.47 V, short circuit current 31.4 mA / cm2. We have successfully deposited different ratio of bilayered a-Se/h-Se selenium films on the metal precursor layers using APPECVD and then obtain high efficiency CIGS solar cells.