| 摘要: | 為了克服能源危機及環境汙染的問題，太陽能是ㄧ極佳的選項，所以可透過太陽能發電以解決此問題。而利用高效率(> 20%)太陽能電池可以減少用地面積以降低其建構成本，其中異質接面矽晶太陽能電池促成高效率太陽能電池的實現。本研究利用射頻電漿輔助化學氣相沉積(Radio-frequency plasma enhanced chemical vapor deposition, RF-PECVD)系統來製備異質接面矽晶太陽能電池中的本質與乙硼烷摻雜氫化非晶矽(a-Si:H)薄膜堆疊結構，藉由調變射頻功率(RF power)、乙硼烷氣體流量(B2H6 flow)、基板溫度(Substrate temperature)、電極間距(Electrode distance)、製程壓力(Pressure)與總進氣量(Total flow)等製程參數探討硼摻雜a-Si:H薄膜電特性之影響。在薄膜沉積製程中首先以光放射光譜儀(Optical emission spectroscopy, OES)和四極柱質譜儀(Quadrupole Mass Spectrometry, QMS)監測電漿物種變化；然後使用四點探針薄膜電阻量測儀(Four point sheet resistance meter)、橢圓偏光儀(Ellipsometer) 、霍爾效應分析儀(Hall)、二次離子質譜儀(Secondary ion mass spectrometer, SIMS)量測薄膜結構與電特性；最後以光電導生命週期量測儀 (Photoconductance lifetime tester)測量此堆疊結構中少數載子生命週期(Lifetime)以得知矽晶鈍化品質優劣。所獲得優質鈍化及導電性的堆疊結構，未來將應用於異質接面太陽能電池射極層上，期望能有效提升電池開路電壓與短路電流。
研究結果顯示，在特定的範圍條件下，可利用OES之SiH*光譜來推測出沉積速率等正比關係、B/Ar與薄膜導電性成正比，並利用Hα/Si*來推測結晶率，綜合以上光譜與薄膜特性之關聯性來做為往後薄膜再現性評估標準，而在調變參數的情況下，隨著硼摻雜氫化非晶矽薄膜中的硼原子量提升，能有效增加薄膜導電特性，但過多的硼原子相對會造成缺陷密度提升，不但造成載子生命週期降低，更會影響薄膜中硼原子的活化，所以找出保有良好電性以及載子生命周期高的薄膜是重要的關鍵。其最終優化結果顯示，體電阻率最低能達到0.0026 ohm-cm，摻雜濃度能達1.25*1020 /cm2，本質堆疊硼摻雜氫化非晶矽層能進一步提升本質層鈍化效果，其堆疊過後載子生命週期為813.37 us，隱開路電壓(Implied Voc)可達0.696 V。
;In this study, the intrinsic/boron doping hydrogenated amorphous silicon (a-Si:H) double structure was prepared by radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD). PECVD has several advantages, such as higher compactness of deposited layer, good step coverage, low operation temperature and good passivation properties of deposited layer. The process parameters such as substrate temperature, radio-frequency power, electrode distance, B2H6 flow, pressure and hydrogen dilution ratio that effected the boron doping a-Si:H thin films were investigated. The Quadrupole Mass Spectrometry (QMS) and Optical Emission Spectroscopy (OES) were used for analyzing the plasma characteristics. The Ellipsometer, Four Point Sheet Resistance Meter, Hall measurement, Secondary Ion Mass Spectrometer and Photoconductance lifetime tester were used to obtain the optical and physical properties of films.
The results show that under certain conditions, the SiH * and ratio Hα / Si * of OES spectra can be used to infer the deposition rate and the crystallization rate. The ratio B / Ar of QMS can be used to infer the conductivity of film. Based on the above correlation on spectra and film characteristics, the process repetitivity can be assessed. While changing parameters, the effect on the film that has the good conductivity and the carrier lifetime is most critical. When the amounts of the boron atoms increase, the conducting properties of the boron-doped hydrogenated amorphous silicon thin film increase effectively. However, too much boron atoms increase densities of the defects, thus reduce the carrier lifetime and affect the activation of boron atoms in films. The optimization result shows that the intrinsic/boron doping hydrogenated amorphous silicon (a-Si:H) double structure can enhance the effect of the passivation, and effectively enhance the open circuit voltage in the HIT solar cell. |
