不同表面結構與水溶液製程條件對薄矽基板有機太陽能電池的影響

混合型太陽能電池利用低溫水溶液製成，可用於未來的薄矽基(<100μm)的光電元件。我們過去的研究中發現表面金字塔能改善元件的反射率，以及提高有機導電薄膜(PEDOT:PSS)的覆蓋率，在元件製程中相當重要。而我們希望進一步在金字塔表面尋找適合的表面結構以提升混合型太陽能電池的電性表現。在我的研究中，結合微米金字塔和奈米結構，稱為Hierarchical結構。透過改變銀粒子在表面的分布，以及調變金屬輔助化學蝕刻液的比例，便可得到多元的表面結構。實驗中，我使用15及30奈米的銀薄膜，搭配快速熱退火，以及控制蝕刻液中氫氟酸和雙氧水的比例為60%、77%、94%。如此優化過的Hierarchical元件能夠在主動區為1x1平方公分的元件上得到14.1%的高轉換效率。另外我們研究在三種不同基板厚度：180μm、100μm、50μm的元件表現。在50μm的超薄矽基板下目前可以做到11%的轉換效率。我們也透過調整銀電極的遮光率，成功的製作出2x2平方公分的元件，並且在50μm的元件上維持良好的電性表現。最後將透過快速熱退火搭配不同蝕刻液比例所蝕刻出的新Hierarchical元件應用在4平方公分的大面積元件上，由於良好的短路電流密度，使得在14%的遮光率下能夠達到13.57%的高效率。而在100μm的結果也有12.85%的優異效率。

關鍵字

矽基板；金屬輔助化學蝕刻；混合型太陽能電池；快速熱退火

並列摘要

Hybrid organic silicon solar cells employs low-temperature solution processes of and thus are viable for future silicon photovoltaics involving thin wafers (thickness <100μm). In the past, our studies have shown that the surface textures of silicon plays an important role on the device performance, which are mainly reflected on the anti-reflective property and surface coverage of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). As a result, researching a proper surface template is imperative to the development of hybrid organic solar cells. In this work, we investigate a compound micro-and nano-scale surface textures, namely hierarchical structures. The templates are modulated through controlling the morphology of silver nano-particles on randomly distributed micro-pyramidal surface and the ratio of hydrogen fluoride (HF) and hydrogen peroxide (H2O2) during metal assisted chemical etch. Specifically, a thin silver film, ~15-30nm in thickness, is thermally evaporated, followed by rapid thermal annealing, and the ratio of HF to (HF+H2O2) is varied from 60% to 94% The device with an optimized hierarchical template exhibits a power conversion efficiency (PCE) of 14.1% with a 1x1 cm2 active area. Next, we investigate the device characteristics with three different substrate thicknesses: 180, 100 50μm, where we can still achieve a PCE of 11% on the 50μm-thick device. And we also modify the grid ratio of the frontal silver electrodes, we can successfully scale up the device area to 2x2 cm2, which maintaining good device performance on the 50μm-thick substrate. Finally, we use the new hierarchical on 2x2 cm2 device, when the ratio is 14%, the efficiency can reach to 13.57% because of the high current density. And we try to use the new hierarchical on thin substrate, when the thickness is 100μm, the efficiency can also reach to 12.85%.