在玻璃基板上製備摻鎵氧化鋅薄膜之表面形貌及光電性質的研究

Abstract

本研究以兩種不同的沉積製程─常壓化學氣相沈積法及靶材濺鍍的方式去製備摻鎵氧化鋅（ZnO:Ga）作為前電極材料，並應用於非晶矽薄膜太陽能電池。利用常壓化學氣相沈積法具有隨機分布的團狀沉積顆粒，沉積約略五、六十奈米的氧化矽透明膜層，並藉由控制氧化矽化學反應前驅物的濃度，我們可以獲得一系列不同光學霧度的氧化矽薄膜。接著，將這一系列的氧化矽薄膜，以靶材濺鍍的方式沉積上一微米的摻鎵氧化鋅膜層並以爐管進行高溫退火的處理。最後，以電漿輔助化學氣相沉積及濺鍍製程，在這一系列的摻鎵氧化鋅基板上製備相同條件之非晶矽吸收層(三百奈米)、氧化鋅背電極(八十奈米)及銀電極(一微米)而完成太陽能元件。 薄膜的量測結果主要分為兩個部分:有機矽烷膜層及摻鎵氧化鋅基板。在有機矽烷膜層的量測及分析方面，我們對這一系列的薄膜作傅立葉轉換紅外線光譜量測，以了解薄膜的化學成分及其鍵結情形，並以分光光譜儀進行薄膜光學特性(穿透度、霧度)的比較。在摻鎵氧化鋅基板方面，其光電性質的量測主要以(電性)霍爾量測儀、四點探針及(光性)分光光譜儀為手段，以測得一系列不同粗糙程度的基板在整體光電性質上的變化；在材料分析中，以薄膜低掠角X光繞射分析法測定成長方向的分布及結晶率上的變化，並探討其與電性、表面形貌的關係。其他方面，原子力顯微鏡與電子顯微鏡亦為應用在詳細的表面形貌掃描及薄膜晶粒成長的微觀察的手段之一。 再者，將原子力顯微鏡量測得到的表面輪廓數據及橢圓儀測定得到的材料折射、消光係數的數據，匯入至運用時域有限差分法(FDTD method)之光學模擬軟體，進行一系列有關光穿透率、電場強度及其應用在元件中對光電流產生的影響。最後，以太陽光電流─伏特量測系統，量測及探討不同粗糙程度摻鎵氧化鋅基板在太陽能電池元件上所造成的效率差異。

In this study, double-pattern textured gallium doped zinc oxide (GZO) films were achieved by inserting rough organosilicon (SiOx) films deposited by Atmospheric-pressure Plasma chemical vapor deposition (APCVD) between sputtered GZO films and glass substrates. The optical and electrical properties of theses GZO films were controlled by the haze ratio of rough organosilicon films. All GZO substrates were thermally annealed in high vacuum to improve film quality. In the end, these GZO substrates were also applied as front contacts in amorphous silicon thin film solar cells. Organosilicon films were analyzed by FTIR to discuss the chemical composition and bonding. The optical properties were measured by spectrophotometer and the electrical properties were measured by Hall Effect measurement and four-point probe. Comparison of the flat GZO / different haze ratio of GZO substrates, we discussed the relation between roughness and eletro-optical characteristics. Besides, the growth orientation and crystallinity were evaluated by X-ray diffraction patterns. AFM and SEM were used to observe the substrate morphology, too. We inputted the raw data of surface morphology and refractive index, extinction coefficient of materials to the FDTD optical simulation software. Transparency, electric field intensity and generation current in solar device were acquired after simulation. Finally, we measured the performance of solar cells with I-V curve and investigate the interference between flat substrate and textured substrates.