應用於三接面薄膜太陽能電池之寬能隙非晶矽氧上電池開發與研究

Abstract

為了三接面太陽電池而開發的寬能隙非晶矽氧電池在本文被研究之。非晶矽氧單接面太陽電池藉著電漿輔助化學氣相沉積技術被沉積。第一部分，高穿透率及高電導的p型非晶矽氧薄膜被研究之。藉著二氧化碳當作沉積的來源氣體，氧原子可以含入膜中。含入膜中的氧擴大了能隙，使光穿透率提升，但電導下降，可歸因於缺陷增多導致。藉著乙硼烷當作沉積的來源氣體，硼原子可以含入膜中，進而造成活化能減少，而提升內建電位。此較佳參數所沉積的p型非晶矽氧薄膜特性為能隙2.03 eV，活化能0.51 eV，電導為2.96×10-7S/cm。第二部分，我們開發了未摻雜的非晶矽氧薄膜為了短波長的光譜吸收。能隙工程也被應用在未摻雜的非晶矽氧薄膜，以期減少p/i介面的能帶不連續。我們應用能隙為1.87 eV的未摻雜非晶矽氧薄膜當作吸收層、能隙為1.96 eV的未摻雜非晶矽氧薄膜當作緩衝層、能隙為2.03 eV的摻雜非晶矽氧薄膜當作p型層。最佳化的單接面太陽能電池為250 nm吸收層厚度，其效率為4.83%、開路電壓為900 mV、短路電流為9.00 mA/cm2，填充因子為59.0%。最後，我們採用最佳化的非晶矽氧單接面太陽能電池，用於非晶矽氧/非晶矽鍺雙接面太陽能電池及非晶矽氧/非晶矽鍺/微晶矽三接面太陽能電池上。為了使各個子電池彼此達成電流平衡，我們調整子電池的未摻雜層厚度。最佳化的三接面太陽能電池的效率為9.16%，其中開路電壓為1.99 V，短路電流為6.60 mA/cm2，填充因子為69.8%。比較含有非晶矽氧電池的單接面、雙接面電池、三接面電池，可以發現光譜分段吸收可以藉著多接面太陽電池達成。因此，廣波段的太陽能可以被吸收而達成更高效率。

The wide bandgap hydrogenated amorphous silicon oxide (a-SiOX:H) solar cell for triple-junction solar cell application has been investigated. The a-SiOX:H single-junction solar cells was deposited by plasma-enhanced chemical vapor deposition (PECVD) technique. First, the p-type a-SiOX:H layer with high transparency and conductivity was studied. By using CO2 as the source gas, the oxygen atoms can be incorporated into the film. The oxygen incorporation widened the bandgap so that the transparency was enhanced, but reduced the conductivity which can be referred to the increase in defects in the film. By using B2H6 as the source gas, the boron atoms can be incorporated into the film, which led to reduction of the activation energy enhancing the build-in potential. The optimal p-type a-SiOX:H with bandgap of 2.03 eV, activation energy of 0.51 eV, and conductivity of 2.96×10-7 S/cm have been achieved. Second, we developed undoped a-SiOX:H for short wave-length spectral response. Bandgap engineering was also applied to undoped a-SiOX:H for the purpose of reducing band discontinuity between p/i interface. We applied a-SiOX:H with bandgap of 1.87, 1.96, and 2.03 eV as the absorber, buffer layer, and p layer, respectively. The optimal single-junction solar cell with a 250 nm-thick absorber had efficiency of 4.83%, VOC of 900 mV, JSC of 9.00 mA/cm2, and F.F. of 59.0%. Finally, we employed the optimized a-SiOX:H single-junction cell to a-SiOX:H/a-Si1-XGeX:H tandem and a-SiOX:H/a-Si1-XGeX:H/μc-Si:H triple-junction solar cells. To balance the current between each sub-cells, we adjusted the thickness of undoped layer in the sub-cells. The optimal cell efficiency of triple-junction solar cell was 9.16% with VOC=1.99 V, JSC=6.60 mA/cm2 and F.F.=69.8%. Compared to single, tandem, and triple-junction cells with the a-SiOX:H cell, it can be seen that the spectrum splitting can be achieved by multi-junction cells. Therefore, the board-band solar energy can be absorbed to achieve higher efficiency.