利用大氣電漿技術沉積不同結晶性硒薄膜於堆疊金屬前驅層之硒化製程研究

Abstract

本論文利用大氣電漿輔助化學氣相沉積法去成長硒膜於銅銦鎵前驅層上，大氣電漿輔助化學氣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，硒的原料利用率相較於共蒸鍍系統有較好的表現。另外在本篇論文中利用快速高溫處理製程進行硒化，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，其優點為製程快速且可減少In2Se之損耗。我們將研究不同的電漿瓦數和基板溫度對硒膜表面形貌、粗糙度、結構、元素組成的影響，分為退火前和退火後兩階段探討。我們預期利用硒的激發態增加銅銦鎵硒薄膜黃銅礦結構的結晶性，進而改善銅銦鎵硒太陽能電池的效率。接著我們將完成太陽能電池，其結構為鋁電極/氧化銦鍚/氧化鋅/硫化鎘/銅銦鎵硒/鉬背電極/鈉鹼玻璃，元件面積為0.48平方公分利用並I-V曲線量測系統、太陽光模擬系統和外部量子效應量測元件電性。量測結果為基板未加溫下，沒加電漿的元件其轉換效率為4.694%，有加電漿的元件最高轉換效率為5.031%；加電漿50W情況下，基板未加溫轉換效率為2.266%，基板溫度為125℃之元件轉換效率為6.103%，此元件填充因子為0.428、開路電壓0.41V、短路電流34.815 mA/cm2。我們的研究成功利用大氣電漿輔助化學氣相沉積法沉積不同結晶性之硒膜於金屬前驅物並熱退火後形成銅銦鎵硒薄膜，最後製成太陽能電池。電漿的效應為提升銅銦鎵硒薄膜的結晶性，基板溫度則提高銅銦鎵硒薄膜的能隙，進而改善元件的效率，且降低成本。

In this paper, we used the APPECVD system to deposit the selenium films on the Mo/SLG substrate. The APPECVD is a non-vacuum system and has the similar ability of large area of sputtering. And it has smaller amount of Se material which can be used than co-evaporation system does. In this work, we presented the RTP process as selenization process, which can decrease depletion of In2Se and is able to accelerate fabrication. We investigated the plasma power and substrate temperature for affecting surface morphology, roughness, structure and composition during the time before and after selenization. We were expecting the degree of crystalline chalcopyrite structure of CIGS films could be improved by radical Se and then so is conversion efficiency of device. Afterwards, we completed solar cell, and its structure is composed by Al/ITO/ZnO/CdS/CIGS/Mo/SLG, which area is 0.48 cm2. The electric properties of CIGS solar cell were measured by I-V curve measurement system with Solar Spectral Irradiance: AM1.5G and extra quantum efficiency. The highest conversion efficiencies of solar cell device without plasma and with plasma are respectively 4.694% and 5.031% at the substrate temperature is 45℃. The conversion efficiency of solar cell device with plasma while power is 50W is 2.266% at the substrate temperature is 45℃. The conversion efficiency of solar cell device with plasma while power is 50W is 6.103% at the substrate temperature is 125℃, which FF=0.428, Voc=0.41V and Jsc=34.815 mA/cm2. In our final study, we completed to deposit selenium thin films of different crystallization on stacked metal precursor and form chalcopyrite structure of Cu(In,Ga)Se2 thin films. Consequently, Cu(In,Ga)Se2 thin films enabled us to fabricate the solar cell device. The effect of plasma enhances the crystallization of chalcopyrite structure of Cu(In,Ga)Se2 thin films. The effect of substrate temperature raised the band gap of Cu(In,Ga)Se2 thin films. According to the above-mentioned, those two effects can improve the conversion efficiency of solar cell device and reduce the costs by APPECVD.