臺灣博碩士論文加值系統

有機太陽能電池(Organic solar cell, OSC)具有大面積製作和低成本以及可以製作在可撓基板上，而這些優點是矽太陽能電池沒有辦法實現的。不幸地，到目前為止有機太陽能電池效率非常的差。因此，目前改善有機太陽能電池的效率是一個重要的課題。然而，改善有機太陽能電池效率的方法有1.改變主動層材料2.光陷阱結構3.退火4.使用電子傳輸層。
在本研究中，有機太陽能電池結構為：ITO/CuPc/C60/ETL/Al。主動層材料有CuPc和C60，PBD、Alq3、BCP當作電子傳輸層材料，氟化鋰和氟化鉀當作修飾層。
在本研究中，分別去找出每一層有機材料的最佳厚度。並且對於其它電子傳輸層材料而言，擁有BCP的有機太陽能電池之短路電流有大幅改善。最主要是因為BCP具有低電子注入能障、高吸收率、表面平坦，而這些結果是藉由能階圖、UV/vis 吸收光譜圖、AFM結果所分析得到。
為了再進一步改善有機太陽能電池的效率，我們在有機太陽能電池擁有BCP中加入極薄的氟化物。從實驗結果可知，BCP能夠改善功率轉換效率，從0.54%提升到0.64%。

The organic solar cells (OSC) have several superior advantages to inorganic solar cells, including lower cost, larger fabrication area, lighter weight and flexible property. Unfortunately, the power conversion efficiency (PCE) of the OSC is quite poor at the present time. Thus, improvement of PCE is an important issue. And then there are improvement methods of OSC from introduction of device concept such as change in active material, light harvesting structure, annealing and the electron transport layer (ETL).
In this study, the structure of small-molecule OSC with is ITO-coated glass substrate /Copper phthalocyanine (CuPc) / fullerene (C60)/electron transport layer (ETL)/Al. The active layer is composed of CuPc and C60. 2-(4-Biphenylyl)-5-(4-tert-butylphenyl)-1, 3, 4-oxadiazole (PBD), Aluminum tris(8-hydroxyquinoline) (Alq3) and bathocuproine (BCP) are used as an electron transport layer. The materials of LiF and KF are used as a modification layer.
In this study, the thicknesses of each material have been optimized for a better PCE. Besides, the short current density (Jsc) of devices with BCP layer was greatly improved compared with that of other ETL materials. The superior properties of BCP, such as lower electron injection barrier, higher UV/vis absorption efficiency and lower surface roughness, have been demonstrated by the energy level diagram, UV/vis absorption spectra and atom force microscope (AFM) data.
In order to further improve the PCE of devices, we add ultra-thin fluoride as a modification layer to the devices with BCP layer. The PCE of OSC is improved from 0.54 % to 0.64 %.

Contents
Chapter 1 Introduction-------------------------------------------------------------------------1
1-1 This history of solar cell-------------------------------------------------------------------1
1-2 The history of organic solar cell----------------------------------------------------------2
Chapter 2 Theory of solar cell---------------------------------------------------------------6
2-1 Solar spectrum------------------------------------------------------------------------------6
2-2 Working principle of solar cells----------------------------------------------------------8
2-2-1 Light absorption-----------------------------------------------------------------------8
2-2-2 Charge separation----------------------------------------------------------------------8
2-2-3 Charge transport-----------------------------------------------------------------------8
2-3 Performance analysis----------------------------------------------------------------------8
2-3-1 Dark current and photocurrent-------------------------------------------------------9
2-3-2 Voc and FF and PCE-----------------------------------------------------------------10
2-3-3 Shunt resistance (Rsh) and series resistance (Rs)--------------------------------11
2-3-4 The quantum efficiency and spectral response-----------------------------------12
2-3-5 Temperature effect-------------------------------------------------------------------13
2-3-6 Limits to solar cell conversion efficiency-----------------------------------------14
2-4 Principle of operation and devices concept--------------------------------------------15
2-4-1 Homojunctions-----------------------------------------------------------------------15
2-4-2 Heterojunction------------------------------------------------------------------------17
2-4-3 Dispersed Heterojunction-----------------------------------------------------------17
2-4-4 Organic solar cell materials---------------------------------------------------------18
Chapter 3 Experiment procedure--------------------------------------------------------21
3-1 The etching and cleaning of ITO substrate--------------------------------------------35
3-2 The functions of organic materials-----------------------------------------------------35
3-3 Deposition of organic thin films and electrode---------------------------------------35
3-4 Measurements-----------------------------------------------------------------------------36
3-5 Materials-----------------------------------------------------------------------------------36
Chapter 4 Results and discussion---------------------------------------------------------25
4-1 Properties of CuPc and C60--------------------------------------------------------------25
4-2 The characteristics of various thicknesses of CuPc and C60 layer for organic solar cells (OSCs)--------------------------------------------------------------------------------26
4-3 The characteristics of various thicknesses of BCP layer for organic solar cells (OSCs)--------------------------------------------------------------------------------------27
4-4 The characteristics of various thicknesses of Alq3 layer for organic solar cells (OSCs)-------------------------------------------------------------------------------------28
4-5 The characteristics of various thicknesses of PBD layer for organic solar cells (OSCs)-------------------------------------------------------------------------------------29
4-6 Effect of optimal of ETL for organic solar cells (OSCs)----------------------------30
4-7 Energy level diagram---------------------------------------------------------------------31
4-8 Absorption spectra------------------------------------------------------------------------32
4-9 Surface morphology----------------------------------------------------------------------33
4-10 The characteristics of various thicknesses of LiF layer for organic solar cells (OSCs)-------------------------------------------------------------------------------------35
4-11 The characteristics of various thicknesses of KF layer for organic solar cells-----------------------------------------------------------------------------------------36
4-12 Comparison for optimal thicknesses of LiF and KF layer as interlayer----------------------------------------------------------------------------------38
4-13 Effect of silver as cathode on the organic solar cells-------------------------------38
Chapter 5 Conclusion--------------------------------------------------------------------------39
5-1 Conclusions--------------------------------------------------------------------------------54
5-2 Future work--------------------------------------------------------------------------------55
References------------------------------------------------------------------------------------------41

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