臺灣博碩士論文加值系統

在本研究中，最徍化結構是從一般常用的結構ITO/CuPc (20nm)/C60 (30nm)/BCP(10nm)/Al調整元件主動層的厚度與結構，使得短路電流3.09 mA/cm2上升到5.11 mA/cm2，開路電壓從0.4V上升到0.47V，轉換效率從0.66%上升到1.28%在AM1.5G的太陽能光譜下。這些增加是歸因於在光的吸收效率和載子的分離效率以及載子的收集效率之間達到一個最佳的平衡，使得短路電流能有所提升而不會影響到元件的填充因子的值。最後得到有機太陽能電池最佳化結構為：ITO/CuPc (10nm)/CuPc:C60 (20nm)/C60 (20nm)/BCP(10nm)/Al。。
為了更進一步地增加元件的效率，我們在最佳化結構的基礎下，在ITO及CuPc之間插入PEDOT: PSS(有摻雜sorbitol)與pentacene雙層陽極緩衝層來幫助元件電洞的收集效率，元件的結構為ITO/PEDOT: PSS (doped with 4wt% sorbitol)/ pentacene (2nm)/CuPc (10nm)/ CuPc: C60 mixed (20nm)/C60 (20nm)/BCP (10nm)/Al。因此藉由雙層陽極緩衝層插入元件使得轉換效率大幅度的增加。短路電流提升了三倍之多，使得元件的轉換效率達到3.9%。

In this study, small molecule organic solar cell with an optimized structure of ITO/CuPc 10nm/CuPc:C60 (20nm)/C60 (20nm)/BCP (10nm)/Al) was fabricated. With optimizing the above structure from the conventional structure of ITO/CuPc (20nm)/C60 (30nm)/BCP (10nm)/Al, the short-circuit current density (Jsc) increased from 3.09 mA/cm2 to 5.11mA/cm2, the open-circuit voltage (Voc) increased from 0.40 to 0.47V, and the power conversion efficiency (ηp) increased from 0.66 to 1.28% under 100mW/cm2 AM1.5G illumination. These improvements were attributed to reach the optimal balance among the light absorption efficiency, the exciton dissociation efficiency and the carrier collection efficiency of the device, resulting in enhancement of Jsc without affecting the value of fill factor (FF) and the reduction of the dark current.
Based on the optimal structure, we incorporated PEDOT: PSS layer doped with 4wt% sorbitol and pentacene layer as interlayers between the ITO anode and CuPc layer to help the hole transport. The small molecule organic solar cell with structure of ITO/PEDOT: PSS (doped with 4wt% sorbitol)/ pentacene (2nm)/CuPc (10nm)/ CuPc: C60 mixed (20nm)/C60 (20nm)/BCP (10nm)/Al. And then the short-circuit current (Jsc) of solar cell was enhanced by inserting both the PEDOT: PSS (4wt% sorbitol) and the pentacene, resulting in a 300% enhancement in power conversion efficiency (PCE). The maximum PCE of 3.9% was obtained under 1sun standard AM1.5G solar illumination of 100mW/cm2.

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--------------------------------------------21
3-2 Deposition of organic thin films and electrode---------------------------------------22
3-3 Measurements-----------------------------------------------------------------------------22
Chapter 4 Results and discussion---------------------------------------------------------24
4-1 The characteristics of HJ and BHJ structured organic solar cells------------------24
4-2 The characteristics of PM-HJ structured organic solar cells (OSCs) with different active layer thickness ----------------------------- --------------------------------------25
4-3 The Voc value of deferent structures---------------------------------------------------27
4-4 The characteristics of PM-HJ structured device with PEDOT: PSS anode buffer layer doped with different sorbitol concentrations ----------------------------------28
4-5 The surface morphology of PEDOT: PSS layer doped with different sorbitol concentrations ----------------------------------------------------------------------------29
4-6 The characteristics of PM-HJ structured device with PEDOT: PSS (4wt% sorbitol) and pentacene double anode buffer layers--------------------------------------30
Chapter 5 Conclusion and Future work-----------------------------------------------33
5-1 Conclusion--------------------------------------------------------------------------------33
5-2 Future work--------------------------------------------------------------------------------33
References------------------------------------------------------------------------------------------34








Figure captions
Figure 1.1 Oil prices, 1861-2006-------------------------------------------------------------------38
Figure 2.1 Solar spectrum---------------------------------------------------------------------------39
Figure 2.2 The equivalent circuit of a solar cell--------------------------------------------------40
Figure 2.3 I-V characteristics of solar cell--------------------------------------------------------41
Figure 2.4 The equivalent circuit of solar cell with Rs and Rsh-------------------------------42
Figure 2.5 Plots of the equation for various combinations of the series and shunt resistance---------------------------------------------------------------------------------43
Figure 2.6 Schematic energy-band diagram of a simple device consisting of single organic layer between two metal contacts-----------------------------------------------------44
Figure 2.7 Schematic of energy-band diagram of a donor-acceptor heterojunction--------------------------------------------------------------------------45
Figure 2.8 A blend of two polymers---------------------------------------------------------------46
Figure 2.9 A blend of one polymer with electron accepting nanoparticles or fullerene----------------------------------------------------------------------------------47
Figure 4.1 The configuration of (a)HJ, BHJ, PM-HJ structured OSC , (b)PM-HJ structured OSC with anode buffer layer in the experiment--------------------------------48
Figure 4.2 Schematic energy levels of the device-----------------------------------------------49
Figure 4.3 J-V characteristics of the HJ device (ITO/CuPc (20nm)/C60 (30nm)/BCP (10nm)/Al) and the BHJ device (ITO/CuPc:C60 (50nm)/BCP (10nm)/Al)--------50
Figure 4.4 The absorption spectrum of pure CuPc and C60 deposited on ITO substrate ---------------------------------------------------------------------------------------------------------51
Figure 4.5 Current-voltage characteristics of hybrid PM-HJ B (ITO/CuPc (10nm)/CuPc: C60 (25nm)/C60 (15nm)/BCP (10nm)/Al) and hybrid PM-HJ C (ITO/CuPc (15nm)/CuPc: C60 (25nm)/C60 (10nm)/BCP (10nm)/Al). ---------------------52
Figure 4.6 (a) Rs, (b) FF, (c) Jsc, and (d) PCE of the device ITO/CuPc (10nm)/CuPc:C60 (25nm)/C6nm)/BCP (10nm)/Al as a function of the thickness of C60 layer.--53
Figure 4.7 J-V characteristics of the PM-HJ structured solar cells without and with PEDOT: PSS doped with different sorbitol concentrations- -----------------------------54
Figure 4.8 The surface morphology of (a) ITO and (b) the PEDOT: PSS layer spin-coated on the ITO---------------------------------------------------------------------------------55
Figure 4.9 The roughness of PEDOT: PSS layer doped with different sorbitol concentrations spin-coated on the ITO----------------------------------------------56
Figure 4.10 The Rs and the Jsc as a function of the pentacene layer thickness--------------57
Figure 4.11 The surface morphology of (a) ITO/pentacene (2nm) and (b) ITO/PEDOT:PSS (4wt% sorbitol)/pentacene (2nm)-------------------------------------------------58
Table captions
Table 1.1 Efficiency of solar cells-----------------------------------------------------------------59
Table 2.1 Integrated Solar Energy Received Annually in Various Countries---------------60
Table 4.1 Photovoltaic performance parameters of different devices ------------------------61
Table 4.2 The parameters of device ITO/CuPc (xnm)/CuPc:C60 (20nm)/C60 (20nm)/BCP (10nm)/Al as a function of the thickness of CuPc layer---------------------------62
Table 4.3 The I-V characteristics of ITO/CuPc (20nm)/C60 (30nm)/BCP (Xnm)/Al-------63
Table 4.4 The conductivity of PEDOT: PSS layers doped with different sorbitol concentrations---------------------------------------------------------------------------64
Table 4.5 Photovoltaic performance parameters of ITO/PEDOT: PSS (4wt% sorbital)/pantancene (Xnm)/CuPc (10nm)/CuPc: C60 (20nm)/C60 (20nm)/BCP (10nm)/Al as a function of pentacene layer thickness------------------------------65

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