噴射式大氣電漿系統鍍製霧度導電薄膜應用於鈣鈦礦太陽能電池前電極

Abstract

如何提升太陽能電池的光電轉換效率是個很重要的議題，許多研究透過增加太陽能電池前電極的霧度性質(Haze factor)增加光於電池內的散射，使入射光在進入電池後的路徑長增加，提高光的捕捉率進而提升電池的光電轉換效率，但尚未有研究將霧度電極應用於旋塗法製作的鈣鈦礦太陽能電池，且霧度電極的製備過程通常需要多次製程，例如蝕刻基板、蝕刻薄膜或在薄膜沉積前舖上霧度增加層(Haze enhanced layer)，使薄膜製備的過程變得繁瑣耗時。本研究使用噴射式大氣電漿系統(APPJ)透過簡單改變製程參數製備中、低霧度的鎵摻雜氧化鋅(Gallium-doped zinc oxide, GZO)薄膜(H = 1 ~ 10%)，及共摻雜法(Co-doping)鍍製高霧度的鎵鋯共摻雜氧化鋅(Ga and Zr co-doped zinc oxide, GZO:Zr)薄膜(H = 35%)，並將其應用於旋塗法製作的鈣鈦礦太陽能電池探討霧度前電極對電池效率的影響。其中發現高霧度的GZO:Zr薄膜製成之電池效率表現最差，最佳僅有5.5%的光電轉換效率、13.7 mA/cm2的短路電流密度、0.912 V的開路電壓與44.6%的填充因子；低霧度的GZO薄膜製成之電池有最好的效率表現，最佳的元件性能擁有11.0%的光電轉換效率、18.7 mA/cm2的短路電流密度、1.047 V的開路電壓及57.6%的填充因子，因為霧度電極的表面粗糙度高，會造成電池在製作時溶液旋塗不均勻，不僅使鈣鈦礦層長晶狀況不佳，還會增加各層間的接觸電阻，導致開路電壓下降與串聯電阻上升，此外，鈣鈦礦太陽能電池的厚度非常薄，霧度電極的粗糙表面容易刺穿鈣鈦礦層造成電池短路，使並聯電阻下降並降低填充因子，最終導致電池光電轉換效率不佳。

Improving solar cell power conversion efficiency is of great importance and has been a hot topic in academia and industry. Many studies have increased the light scattering by increasing the haze factor of the front electrode of the solar cell so that the incident light has a longer path length after entering the cell, which increases the light trapping and thus improves the power conversion efficiency (PCE). However, most prior works have focused on conventional solar cells, and there are no reports about applying haze electrodes to the perovskite solar cells fabricated by spin coating, despite perovskite solar cells have shown high promise in low cost and high efficiency. Furthermore, the preparation process of hazy electrodes usually requires multiple processes, such as etching the substrate, etching the film, or applying a haze-enhanced layer before film deposition, which makes the electrode preparation process tedious and time-consuming. In this study, Gallium-doped zinc oxide (GZO) films with medium and low haze (H = 1 ~ 10%) were prepared by simply changing the process parameters using the atmospheric pressure plasma jet system (APPJ), and high haze Ga and Zr co-doped zinc oxide (GZO:Zr) thin films (H = 35%) were deposited by co-doping. We then applied those as the front electrode of perovskite solar cells fabricated by spin coating and investigated the effect of the haze electrodes on the PCE. It was found that the PCE for the highly hazy GZO:Zr case had the worst performance—the best PCE was only 5.5%, the short-circuit current density was 13.7 mA/cm2, the open-circuit voltage was 0.912 V, and the fill factor was 44.6%. On the other hand, the cells with the low haze GZO film have the best efficiency performance with the best PCE of 13.0%, a short-circuit current density of 19.7 mA/cm2, an open-circuit voltage of 1.026 V, and a fill factor of 65.7%. The high surface roughness of the haze electrode will cause the uneven coating of the solution during the spin coating, which not only puts the perovskite layer in poor crystal growth condition but also increases the contact resistance between the layers, resulting in a drop in open circuit voltage and an increase in series resistance. In addition, the thickness of perovskite solar cells is very thin, and the rough surface of the haze electrode is easy to spike the perovskite layer, resulting in a short circuit of the cell, reducing the parallel resistance and reducing the fill factor, which ultimately leads the poor power conversion efficiency of the cell.