高分子太陽能之研究：多氟苯衍生物於氧化鋅陰極之表面處理 及其添加於活性層對元件效率提升之影響

Studies on polymer solar cell: Effects of multi-fluoro-substituted derivatives treated ZnO surface as cathode and its addition to active layers on the promotion of device efficiency

鄭宇珊(Yu-Shan Cheng)

指導教授 ： 陳壽安

國立清華大學/工學院/化學工程學系/碩士(2013年)

摘要

摘要
綠能產業儼然成為環保意識逐漸抬頭及石油蘊藏量日漸不足的一道曙光，其中，以汙染最少且效益最可觀的太陽能最受矚目，然而於太陽能電池中，又以可大面積印刷、成本低廉的高分子太陽能電池最有希望成為新一代的綠色能源。影響高分子太陽能電池效率的變因相當多，機制也略為複雜，一般而言，其效率取決於其活性層的形貌，目前世界上發展了許多控制形貌的方法，但也由於不同的高分子有不同的特性，並非每一種控制形貌的方式都能夠適用於每一個系統。
由於氟為強拉電子基，會將苯環中心的電子雲密度降低，而使多氟取代的苯環中心形成一個正電中心，這樣的正電中心性質使得多氟苯與多電子的雙鍵、苯環等物種有很強的交互作用力，基於這個概念，在此提出兩種方法來控制活性層形貌並進一步改善元件效率。
第一種方法為混摻入一多氟苯高分子polypentafluorophenyl methacrylate (PPFPA)於活性層內來幫助[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM)排列，然而PC61BM在 PPFPA上的多氟苯取代基的吸引下，可以沿著高分子主鏈排列，進而促使PCBM排列成連續的電子通道，如此的設計可以使效率自3.43 %提升至3.74 %。
二為利用多氟苯衍生物2,3,5,6-Tetrafluoro-1,4-benzenedicarboxylic acid (TFTPA)自組裝單分子層來改質電子收集層ZnO與活性層的介面， TFTPA可以由庫倫作用力吸引PCBM的特性，改質過後的ZnO吸附一層PCBM來使活性層與ZnO的介面接觸更好，而使電子能更順利的傳導至電極且不會在介面處被淬熄。實驗結果顯示利用TFTPA吸附一層PCBM的元件於P3HT: PC61BM系統之效率相較於未處理的元件可以自3.02 %提升至4.03 %。然而TFTPA具有相當高的系統相容性，在PTB7:PC71BM的系統當中效率也有相當的提升(自6.03 % 到6.90% )，此顯示了TFTPA改質ZnO實為一快速、簡單、高系統相容性的方法來改善高分子太陽能電池效率。

關鍵字

高分子太陽能電池 ； 多氟苯 ； 單分子自組裝層 ； 富勒烯 ； 介面改質

並列摘要

Abstract
Polymer solar cells (PSCs) are a promising alternative for low-cost renewable energy due to their solution-process ability, flexibility and large-area fabrication. However, the power conversion efficiency (PCE) of PSCs depends on complicated mechanism of carrier generation and transport. In general, the morphology of active layer in PSCs plays a very important role in PCE. Many reports have studied on effective control of morphology but its characteristics are depending on active polymer, making it difficult to establish a general method for controlling the morphology.
Multi-fluoro-substituted benzene has the nature of electron-depleted ring center since the electron withdrawing characteristic of the F-substituents makes the electron density of benzene ring moving to F atoms in the periphery. Thus, multi-fluoro-substituted benzene has the capability to strongly interact with electron-rich species such as double bonds and aromatic rings. Based on this concept, we propose two methods to improve the device performance by controlling morphology of the active layer.
The first method is to add a multi-fluorobenzene substituted polymer, poly(pentafluorophenyl methacrylate）(PFPPA), into active layer as additive. The multi-fluorobenzene can attract the [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and make it align along with the main chain of the PFPPA. The aligned PCBM makes the electron transport easier and thus the PCE is improved from 3.43 % to 3.74 %.
The second method is to modify ZnO surface by incorporating 2,3,5,6- Tetrafluoro-1,4-benzenedicarboxylic acid (TFTPA) on top of it. Upon coating a layer of fullerene derivative on top of it, the fullerene molecules can be physically absorbed via coulombic interaction and facilitate a promoted electron collection from the bulk. Significant enhancement in PCE is observed for the devices with the active layer P3HT:PC61BM (or PC71BM) by promoting from 3.20 to 4.03% (or from 3.27 to 4.04%); and with the active layer PTB7: PC71BM from 6.03 to 6.90 %. This method should be also applicable to other types of active layer.

並列關鍵字

polymer solar cell ； multi-fluorobenzene ； self-assembled monolayer ； fullerene ； interface modification

參考文獻

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