高效率有機/無機混合型異質接面太陽能電池

Abstract

有機/無機混合型太陽能電池與傳統矽基板太陽能電池比較起來成本上節省了許多，這種元件利用無機材料的高光學吸收以及好的載子遷移率，配合上有機材料製程的簡易製程步驟與低廉的價格，結合兩者的優點所成的元件。然而如何使電洞順利傳導過有機層形成的能障仍是這個新穎元件最重要的課題。在這篇論文中，我們成功製作出PEDOT:PSS/Si異質接面混合型太陽能電池，平均轉換效率可達9.84%。為達成有機液態製成矽基太陽能電池的目標。我們利用銀奈米線取代熱蒸鍍銀電極，簡化製程步驟更可改善串聯電阻。最後我們更進步建構了一個模型來模擬此種混合型太陽能電池，其最高效率估計可達20%以上。 在本論文的第一部份我們討論如何製作具有矽奈米線與金字塔表面結構之混合型太陽能電池，其異質接面是由PEDOT:PSS直接旋塗至n型矽基板上所製作。我們發現工業標準的濕蝕刻金字塔結構可加強其抗反射程度以及增加表面面積載子蒐集，並且不會造成矽表面有著過多的傷害。接著我們將正電極替換成旋塗銀奈米線，這些交錯編織狀的銀奈米線造就了高穿透度以及高導電性，並且可以很簡單的旋塗在矽基板上。 第二部分我們研發了一套利用解普瓦松與連續方程式的一維運算系統，藉由實驗推估的材料參數可以計算出元件的能階位置與電流電壓特性，於是我們利用PEDOT:PSS/Si的能帶結構探討其表面效應與載子傳遞機制，我們利用一個很薄的缺陷層來形容PEDOT:PSS與Si之間所存在的缺陷。並且經由此模型估計出混合型太陽能電池改善其反射損耗與材料性質之後，便能達到20%以上的效率。

An organic/inorganic hybrid solar cells are cheap alternatives to conventional silicon-based solar cells. The devices take the advantages of high optical absorption and carrier mobility of inorganic semiconductors, while maintaining the easy processing attributes of polymers or other soft materials. However, the conduction of holes has been a major technical barrier for the advance of such novel devices. In this study, a hybrid PEDOT:PSS/silicon heterojunction solar cell is demonstrated with an average power conversion efficiency of 9.84% using rapid solution-based organic processes. Then we propose the use of silver nanowires (AgNWs) to improve the series resistance of the hybrid solar cells and further to realize solution-processed silicon-based photovoltaics. At last, the modeling of such devices predicts an efficiency exceeding 20% with improved reflection loss and material properties, shedding light into the attainment of high-efficiency and low-cost photovoltaics based on organic/inorganic hybrid devices. In the first section of my thesis, we discuss how to fabricate hybrid heterojunction solar cells with silicon nanowire and pyramidal surface textures. The hybrid heterojunction solar cells are demonstrated based on the composite of conductive polymer PEDOT:PSS directly spun-cast on a micro-textured n-type crystalline silicon wafer. Moreover, the industrial-standard microscale surface textures improve the antireflection and carrier collection without increasing much surface recombination. Then we replace the frontal metal contacts with the coating of AgNWs. The cross-linked AgNWs offer high transparency and low sheet resistance, which can be easily fabricated using low-cost and non-toxic materials. In the second section, we employed a self-consistent drift-diffusion and Poisson solver to theoretically investigate the effects of interface/bulk defects, doping concentration, and back surface recombination on the device performance. With a proper choice of band alignment, the modeling of such devices predicts an efficiency exceeding 20% with improved reflection loss and material properties.