利用轉印製程製備高效率電子元件之研究

Abstract

有機固態太陽能電池近幾年已逐漸受到各界重視，主要原因是其效率雖不如矽晶太陽能電池，但還可達到5~6 %，且其製作成本相較於矽晶太陽能電池來得便宜且簡易，對於可撓性及輕量化方面亦是矽晶太陽能電池所無法比擬的，故科學家才會持續不斷地探討其工作機制與元件效能。雖然有機固態太陽能電池效率表現尚無法運用至耗電量較大之設備上，卻已可操作於小型風扇或電子計算機等耗電量低之電器上。本研究主要目的是藉由轉印製程來製備多層結構電子元件，已達增加太陽能電池光電轉換效率以及有機發光二極體元件效率，在有機太陽能電池中而為了使得有機分子與電極之間的接觸降低，同時又不會失去太多施體與受體之間的介面接觸，所以製備了雙層具有不同P3HT/PCBM的重量比的太陽能電池，此外在有機發光二極體元件中，在電洞注入層與發光層之間插入了一有機薄膜(TFB)降低了電洞注入的能量障礙有效了提高元件效率。 轉印製程成功了製備多層結構的太陽能電池與有機發光二極體元件，在製備上層高分子薄膜時，為了避免溶劑會溶解下層薄膜的問題，我們使用了poly(di-methyl-silane) (PDMS)印章去轉印有機高分子薄膜至基板之上，對於有機太陽能之雙層主動層分為P3HT豐富層(P3HT-rich layer)與PCBM豐富層(PCBM-rich layer)，而對於有機發光二極體元件其主動層之組成為bule-polyfluorene系列之發光層與poly(9,9-di-n-octylfluorene-alt-(1,4-phenylene-((4-sec-butylphenyl) imino-1,4 -phenylene)) (TFB)為電子阻擋層。而我們發現元件之效率表現與轉印的層數息息相關，當最適化每一層條件之後，有機太陽能光電轉換效率可以達到3.52%，而有機發光二極體元件效率與沒有電子阻擋層之元件相比，可使效率提升27% (3.7 cd/A 增加至4.7 cd/A)。

Solid type polymer solar cells (PSCs) have been extensively studied in this decade, although the efficiency is still lower than 5~6%. Its low fabrication cost, easy processing, and flexible property make it attractive to researchers. The PSCs and polymer light emitting diodes (PLEDs) were demonstrated by incorporating multilayer structure through solution process. In order to prevent the dissolution of the bottom layer by the subsequent process, we use a poly(di-methyl-silane) stamp to transfer the active layer onto the target surface. We introduced the strategical multilayer structure by using our previous developed stamping technique. In order to minimize the unfavorable contact between organics and electrodes for bulk heterojunction (BHJ) solar cells while not losing much the donor and acceptor junctions, we studied the bilayer structure which consists of different fraction of poly(3-hexylthiophene) (P3HT)/ [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend layers. Furthermore, in order to balance carrier transport for PLEDs, we also studied the bilayer structure which consists of a bule-polyfluorene as light emitting layer (LEL) and poly(9,9-di-n-octylfluorene-alt-(1,4-phenylene-((4-sec-butylphenyl) imino-1,4 -phenylene)) (TFB) as a electron-blocking layer (EBL). We found that the efficiency of devices was readily manipulated by changing the constitution of each stacking layer. After optimizing the fabrication conditions for each functional layer, we obtained PSCs reaching a power conversion efficiency of 3.52%. The efficiency of PLEDs incorporating an EBL was 27% greater (reaching 4.7 cd A–1) than that prepared without an EBL layer.