高分子太陽能電池– 可撓性元件及多層結構製程技術

Abstract

有機光電元件在效能上至今雖尚無法與無機材料相提並論，但其應用上的廣度更甚於無機光電元件。除了製程及材料的成本大幅降低外，在可撓曲基板上的發展具有高度的應用性，尤以高分子材料所具有的撓曲性更備受矚目。雖然在能源及現今市場需求的角度上，效能的提升是最根本的要求，高效率材料的研發是一直以來學術努力的方向，但可撓性元件將是未來有機光電元件應用的重要領域。 有鑑於此，在本論文的研究重點之一即著重於可撓曲元件的組裝。另一方面，在提升元件表現的方法上，除了研發新材料外，對元件進行各種處理改善有機材料在微結構上的排列在近幾年的研究上日趨成熟。此外，從無機光電元件的發展上可以發現，在複合層結構成功組裝後，理論計算可達的最高效率因此被超越。然而，在多層元件的組裝上尚未有一不失元件表現的方式來進行研究及應用。以小分子來說，多層的結構可以高真空的熱蒸鍍來達成，但其過程較為繁複;而高分子材料雖有溶液製程的方便性，卻因此失去了其多層結構的可能性。如何有效並且方便地藉由多層結構來提升元件的表現成為元件物理上的瓶頸。本論文第二部份，也是最主要的研究，即在討論如何有效地製備多層高分子光電元件來提升其整體效能。 在可撓曲基板的組裝上，我們在元件底部以玻璃支撐，使得可撓曲基本可以旋轉塗佈的方式來製備高分子薄膜。並達到可與玻璃基板比擬的高分子太陽能電池效能(> 3 %)。製作於 6 x 6 cm2大面積的可撓曲基板也以達到將近40 mA的短路電流及1.2 V 的開環電壓。 第二部份中，我們以表面處理過的聚二甲基矽氧烷來進行乾式轉移有機光電薄膜，以此方式成功地製作出不失傳統旋轉塗佈所得薄膜之光電性質，並進一步以複合層結構發展出控制成分分佈的光電轉換層及載子萃取結構來提升元件性能。 綜觀上述，本研究建立了可撓曲有基光電元件的平台並開啟了有機光電複合層元件物理的領域。此平台提供了目前所有高分子光電元件製作於可撓曲基板的捷徑。而此薄轉移的方式更突破了傳統高分子薄膜製程的限制，同時具有製程便利的優點，對於有機光電元件的效率將有更大的進展可能性。

From the engineering point of view, polymer photovoltaics or light emitting diodes gain their advantages over inorganic optoelectronics in the utilization of flexible substrate. On the other hand, efficiency is always the major demand for commercial application. Instead of pursuing device treatment methods and new materials with higher device performance in the field of organic optoelectronics, in this thesis, we devoted ourselves to flexible photovoltaics and new architectures for improving device performance. In the first part of our work, flexible photovoltaics based on conventional P3HT:PCBM bulk heterojunction system were fabricated on PET/ITO substrate. To simplify the procedures, a back glass support was used for spin coater. Upon the optimization of the manufacture technique, efficiency more than 3% has been demonstrated for flexible photovoltaics. Furthermore, large area, flexible device with short current ~40 mA and open circuit voltage ~1.2 V have been achieved. Secondly, film transfer technology through poly(di-methylsilane) (PDMS) for the fabrication of organic optoelectronic thin films has been demonstrated. The transfer process not only overcomes traditional problems on multilayered polymeric structure construction but furnishes the most convenient way for cascade devices fabrication. Through the process, it was found to be a function of the force exerted on PDMS and the target surface, as well as the temperature at which the transfer takes place completely and successfully. The surface morphology of the films grown on PDMS ensure larger surface roughness, thus creating more interface area and comparable conversion efficiency toward traditional process has been manifested. Additionally, benefited from residual free process, cascade structure with donor acceptor distribution control in photoactive layer is successfully demonstrated even higher device performance could be approached in the future. Furthermore, by controlling the surface properties of the stamp, different interaction of the PDMS toward each components on it was supposed to be an fruitful medium for self-organization of organic materials what was preferred for photonic and electronic properties of the organic optoelectronic thin films.