高開路電壓平面異質界面有機光伏元件之施體工程

Abstract

本篇論文旨要藉由施體材料調變製備具有高開路電壓以及高效率之平面異質界面小分子有機太陽能電池元件。首先我們引入一新型態有機施體材料bis(4-(N-(1-naphthyl)phenylamino)-phenyl)fumaronitrile (NPAFN)，相較於有機太陽能電池中常見的施體材料（CuPc），NPAFN具有較高的最高電子佔有軌域，搭配電子受體材料碳60時，可有效提升與C60間之能階差，由傳統CuPc/C60結構之0.6 eV提升至NPAFN/C60結構之1.2 eV，提高元件開路電壓之理論極限並進一步提升元件效率。再經由適當的膜厚及鍍率調變後，其最佳化元件結構具有0.96 V之開路電壓以及2.27%之功率轉換效率。 除了引入新型態有機材料外，我們同時使用傳統具有高開路電壓之有機太陽能電池結構SubPc/C60/BCP，藉由控制蒸鍍鍍率，調變SubPc膜層的之分子排列，藉此改變SubPc之能階分佈以及分子間作用力大小，有效的增加SubPc/C60間的能階差距並減少元件之暗態逆向飽和電流，提升元件的開路電壓以及功率轉換效率，其最佳化之元件具有1.06 V之開路電壓以及3.96%之元件效率。此外，藉由在陽極以及SubPC間引入一層超薄之NPAFN薄膜作為激子阻擋層，可有效降低SubPc膜曾中產生之激子遭陽極淬熄的機率，將SubPc吸收波段之內部量子轉換效率至接近100%，大幅提昇元件之光電流產出。藉由調變NPAFN阻擋層之膜厚，其NPAFN/SubPc/C60/BCP平面異質結構之最佳化元件具有1.09 V之開路電壓，7.05 mA/cm2之短路電流以及4.86%之元件效率。

The objective of this dissertation is to fabricate the planar small molecular organic photovoltaic (OPV) devices with high open-circuit voltage (VOC) by engineering the donor layers of the device. The high VOC OPV device was fabricated by utilizing the new materiall bis(4-(N-(1-naphthyl)phenylamino)-phenyl)fumaronitrile (NPAFN) as the donor materiall and substituted for the conventional donor material cooper phthalocyanine (CuPc) in the OPV device. Compared with the conventional CuPc/fullerene OPV device, the energy level different between the highest occupied molecular orbital (HOMO) of NPAFN and the lowest unoccupied molecular orbital (LUMO) of fullerene (C60) was increased, thus increased VOC and improves the device efficiency. Beside the introduction of the new organic donor material, the high efficiency and high VOC organic photovoltaic device was also fabricated by controlling the deposition rate of SubPc in the conventional SubPc/C60 based OPV device. The molecular packing of SubPc was changed obviously with the deposition rate and thus influenced the energy level of SubPc which energy level different between SubPc HOMO level and C60 LUMO level and also reduce the energy barrier between ITO anode and SubPc, which increase the VOC to 1.06V and enhance the fill factor to 65, result in the obviously improve of the device efficiency to 3.95%. Further more, JSC and the efficiency of SubPc/C60 based OPV device was further improved by inserting an ultra thin NPAFN as the donor buffer layer between the ITO anode and SubPc layer. Due to the exciton blocking characteristic of NPAFN, the JSC value increases and JS value decreases monotonically with increasing NPAFN thickness. However, the low hole mobility of NPAFN results in the increase of serial resistance NPAFN, and hence a dramatically decrease in fill factor. An optimized efficiency value of 4.83% was obtained with 2-nm NPAFN.