以離子佈植製作單晶矽太陽能電池光電特性之研究

The characteristics of single crystal silicon solar cell by ion implantation

朱維屏(Wei-ping Chu)

指導教授 ： 林天財

崑山科技大學/工程學院/電機工程研究所/碩士(2006年)

摘要

太陽能電池為目前除了石油能源外的第二能源，提高太陽能效率則是目前各研發單位研究之重點，本研究是利用離子佈植改變快速退火時間及不同結構來探討太陽能電池元件之光電特性。
研究結果顯示，逆金字塔結構有光封存之效果，可使矽晶圓表面平均反射率由40％降低至10％，也可使太陽能電池效率提升。單層抗反射層可使矽晶圓表面某波段反射呈現破壞性干涉，使整體反射率降低至25％左右，而雙層抗反射層比單層抗反射層的反射率低，且反射率在5%以下之頻寬有變寬現象。雙層抗反射層搭配逆金字塔結構之平均反射率可以降低至3.8%。
離子佈植後，表面晶格結構會經過離子轟擊產生混亂，利用快速退火處理，使表面混亂之晶格結構完整，並且使太陽能電池之短路電流增加。快速退火處理後，可以使離子佈植後之摻雜濃度經退火而擴散，導致減少復合電流及使漏電流變小，使開路電壓變大。電極與矽呈現歐姆接觸對於太陽能電池效率影響大，若有良好之歐姆接觸的電極，可以使太陽能電池之串聯電阻變小，使短路電流電變大，金屬鋯之巨蝻?C，則是一個與N型矽呈現良好歐姆接觸的材料。ITO雖是優良的透明導電膜，因巨蝻?o過高，當作N-矽的電極，所得之短路電流15mA不如金屬鋯電極之短路電流30mA。當照光強度越大時，則短路電流會增加，但光源太強使元件之內部電阻Rsh過小，而輸出電流曲線只呈現電流源串聯電阻Rs之光電流曲線。在照光強度為25mW下，會呈現最大填充因子56.9%，最大效率為2.35%。當照光強度為100mW下，離子佈植後快速退火60秒之逆金字塔結構會有最大電流31.5mA及最大效率1.1%，則因植入離子濃度過多導致內部損失效率過大而效率不高。

關鍵字

離子佈植 ； 太陽能電池

並列摘要

The solar cell is the second selective energy resource besides petroleum in current. Many researchers focus on how to improve solar cell efficiency and to develop a new materials solar cell now. In this study, the photo-electric characteristics of solar cell device were to be investigated by ion-implant technique with different annealing time and with various device structures.
The results showed that the Pyramid structure can decrease light reflection from 40% to 10% for silicon wafer and improve the efficiency of solar cell. When the destructive interference appeared at defined wavelength, the reflection on silicon wafer coated with single anti-reflection layer was redued to 25%. The reflectance of single anti-reflection layer was lower than with double layer, and the wave-band width at below 5% reflection become broaden.
After ion-implant, the silicon lattice was significantly damaged by ion bombardment. To use RTA treatment, the lattice was recrystallized by thermal annealing. This treatment was effective to rise the short current of solar cell and to increase the open circuit voltage. The reasons were that thermal annealing can promote the lattice to be perfect and to decreas the leakage current and recombination current. The interface between electrode and silicon is very important to the solar cell ohmic contact, it can let the series resistance of the solar cell decreased and increase the short circuit current. The work function of the electrode must be relatively lower than the electron affinity of N-type silicon. Otherwise, if the work function is too high, the electron transporting from N-type silicon to metal electrode will exist a large barrier. Zirconium is low working function materials contacting with N-type silicon which show a good ohmic characteristics. Although ITO is the excellent transparent conductive film, but its work function is too high respect to N-type silicon. Thus, the short circuit current of 15mA is not so good as one of 30mA by zirconium electrode. The short circuit current was decreased with increasing illumination intensity, but the resistance of Rsh was smaller at high illumination. The slope of IV curve show linearly, indicating the relation of the Rs resistance but without Rsh. At this condition, the device showed the best FF of 56.9% at under illumination intensity of 25mW, and obtained a maximum efficiency of 2.35%. The maximum current of 31.5mA and efficiency of 1.1% can be measured at the sample of Inverted Pyramids structure at 60 seconds annealing treatment with illumination intensity of 100mW.

並列關鍵字

solar cell ； ion implantation

參考文獻

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