藉由鹼蝕刻技術搭配各種前電極增強網印式負型單晶矽太陽能電池之光電特性研究

本研究藉由氫氧化鉀(KOH)鹼性蝕刻技術調控射極及背電極摻雜濃度並搭配各種正、背電極來增強網印式負型單晶矽太陽能電池的光電特性研究，當施行背電極歐姆接觸擴散後在晶片正面及背面均會產生同質性擴散，因此若再施行第二次射極擴散時無法得到最佳的射極接面，同時射極濃度亦會受到影響，為了改善此現象，利用調控KOH鹼性蝕刻液之濃度、蝕刻時間及溫度等參數將第一次施行背電極歐姆接觸擴散後的背面蝕刻至基板原本的濃度，當蝕刻時背電極歐姆接觸面利用電漿化學氣相沈積氮化矽當作蝕刻保護層，同時利用掃描電子顯微鏡(SEM)觀測表面金字塔形貌，及利用四點探針測量射極及背面之片電阻值。實驗結果顯示，當蝕刻條件在KOH濃度為1.7%，溫度為83 oC及蝕刻時間為10分鐘時可將背電極歐姆接觸擴散後的背面回復至基板原本的濃度，以此技術整合至網印式負型單晶矽太陽能電池其光電轉換效率相對於沒有使用此技術可增加約3%。此外，為了改善金屬前電極與p型射極的金半接面以及研究前、背電極對元件的影響，分別採用銀、鋁、銀鋁膠、銀硼膠做為前電極並進行比較，另一方面，背電極的部分則固定使用銀膠。從本次實驗結果顯示，正、背電極分別使用銀鋁膠(6%)及銀膠所製作出的元件可以得到最好的轉換效率為16.3%，Voc為616mV，Jsc為40.9mA/cm2。因為，銀膠中摻入少量的鋁膠經由加熱後能形成前表面電場，能有效減少表面複合並加強p+射極的特性，此外，銀鋁膠還具備銀膠低電阻率的能力，藉以減少電極的串聯電阻。

關鍵字

氫氧化鉀；網印技術；電極膠

並列摘要

The effects of KOH alkali etching and various electrode pastes on photovoltaic characteristics of screen-printed N-type mono-crystalline silicon solar cells (SPMSSCs) were presented. Firstly, the sheet resistances of the emitters in SPMSSCs were modified by KOH alkali etching after ohmic contact formation in the rear side of SPMSSCs. Furthermore, the P-type emitter in SPMSSCs can be obtained by the boron diffusion paste. The results reveal that compared with the SPMSSC without KOH alkali etching, the achievement of an conversion efficiency (CE) improvement of more than 3% absolute in the SPMSSC with KOH alkali etching was explored. Moreover, to investigate the effects of both front and rear electrodes on electrical characteristics of SPMSSCs, the Al, Ag, AgAl and AgB pastes were used as the front electrodes. On the other hand, the Ag pastes were used as the rear electrodes. The CE of 16.3% can be achieved by AgAl(6%) and Ag pastes as the front and rear electrode, respectively. The enhanced mechanisms could be due to the formation of front surface field (FSF) by the Al doped emitter and low bulk resistivity of Ag film for AgAl paste with around 4-6% Al doping.

並列關鍵字

single-side alkali etching ； KOH ； screen-printing technology ； electrode pastes

參考文獻

[1] M. Lenio, J. Howard, F. Jentschke, A. Lennon and S. Wenham, “Design, Fabrication and Analysis of High Efficiency Inkjet Printed Passivated Emitter Rear Contacted Cells,” Photovoltaic Specialists Conference (PVSC), 2011 37th IEEE, pp. 1095-1100, Jun 2011.

[2] J. Zhao, A. Wang, P. P. Altermatt, S. R. Wenham and M. A. Green, “24% Efficient PERL Silicon Solar Cell: Recent Improvements in High Efficiency Silicon Cell Research,” Solar Energy Materials $ Solar Cells, vol. 41, No. 42, pp. 87-99, 1996.

[4] S. Riegel, F. Mutter, T. Lauermann, B. Terheiden and G. Hahn, “Review on Screen Printed Metallization on P-type Silicon,” Energy Procedia, vol. 21, pp. 14-23, 2012.

[5] M. Moors, K. Baert, T. Caremans, F. Duerinckx, A. Cacciato and J. Szlufcik, “Industrial PERL-type Solar Cells Exceeding 19% with Screen Printed Contact and Homogeneous Emitter,” Solar Energy Materials $ Solar Cells, vol. 106, pp. 84-88, 2012.

[6] J. E. Cotter, J. H. Guo, P. J. Cousins, M. D. Abbott, F. W. Chen, and K. C. Fisher, “P-Type Versus n-Type Silicon Wafers: Prospects for High-Efficiency Commercial Silicon Solar Cells,” IEEE Trans. Electron Devices, Vol. 53, pp. 1893-1901, 2006.

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藉由鹼蝕刻技術搭配各種前電極增強網印式負型單晶矽太陽能電池之光電特性研究

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