利用飛行時間法量測P3HT混合PCBM薄膜的電子遷移率

Abstract

藉由旋轉塗佈(spin-cast)製造的薄膜被廣泛使用在高分子太陽能電池和高分子場效應電晶體。用旋轉塗佈方法製造的薄膜膜厚能控制在300奈米以下。藉由飛行時間法量測垂直載子遷移率，必須使用液滴塗佈(drop-cast)方法製造薄膜以致於光的穿透深度是遠小於整個樣品的厚度。但是使用液滴塗佈方法並不能取代旋轉塗佈的方法，因為這兩種方法會產生不同的薄膜形態，這些不同的薄膜形態會影響載子遷移率。為了量測實際應用在高分子太陽能電池和高分子場效應電晶體的薄膜，我們必須要在Indium Tin Oxide (ITO)玻璃上面加上一層價數產生層，然後在用旋轉塗佈的方法把薄膜製造在價數產生層上面。在實驗中，使用不同重量比的P3HT和PCBM溶在氯苯(chlorobenzene)裡面，並利用液滴塗佈和旋轉塗佈的方法製造薄膜，利用時間飛行法量測這些不同方式製造出來的薄膜的垂直載子遷移率。結果顯示，利用旋轉塗佈製造的膜其電子垂直的遷移率是比用液滴塗佈製造的膜大差不多兩個數量級，這樣的結果可由π-π堆疊的結構來解釋。

Films fabricated by spin-cast technique are used in organic polymer solar cell and polymer light emitting diode. The thickness of spin-cast film could be controlled below 300 nm. In the vertical carrier mobility measured by time of flight, we used drop-cast method to fabricate thick films (several micrometer) that light penetration depth is less than the total thickness of the film. However, the morphologies of the films by spin-cast and by drop-cast are different. The different morphologies would affect the charge carrier mobility. In order to measure the real films used in polymer solar cell and polymer light emitting diode, the charge generation layer is deposited on Indium Tin Oxide (ITO) glass, and the films are fabricated by spin-cast on the charge generation layer. In this work, the different weight ratio of P3HT:PCBM is dissolved in chlorobenzene, and these films are fabricated by drop-cast and spin-cast. The vertical charge carrier mobility of these different film processes are measured by time of flight technique. The results show the vertical electron mobility which film is fabricated by spin-cast is about two orders of magnitude lager than the film fabricated by drop-cast. As the result,