可撓式有機太陽能電池之研製

Study and fabrication of flexible organic solar cells Study and fabrication of flexible organic solar cells

王國龍(Kuo-Lung Wang)

指導教授 ： 莊賦祥

國立虎尾科技大學/電機資訊學院/光電與材料科技研究所/碩士(2008年)

摘要

本研究分為兩大部分，分別為小分子與高分子有機太陽能電池。第一部份為小分子部分，利用Pentacene及C60製作有機薄膜太陽能電池(organic solar cells)。在ITO基板上先旋轉塗佈一層PEDOT:PSS，改善ITO表面平整度因而增加有機薄膜太陽能電池之光電轉換效率由0.49%提高至0.58%。接著於PEDOT:PSS溶液中添加不同濃度之Glycerol，以增加PEDOT:PSS之導電率，進而提高有機薄膜太陽能電池元件之短路電流，當Glycerol濃度為4%可將效率由0.58%提高至0.62%。若再將元件置於加熱器(Hotplate)上進行熱退火處理(Annealing)，可提高C60薄膜之吸收效率，並改善Pentacene/fullerene(C60)之界面特性，進而大幅提升有機薄膜太陽能電池之光電轉換效率，由0.62%提高至0.84%，Voc=0.32V，Jsc=6.61mA/cm2。第二部分為可撓式高分子太陽能電池部分，本研究混合poly(3-hexylthiophene)(P3HT)及[6,6]-phenyl-C61 butyric acid methyl ester (PCBM)作為元件主動吸光層(active layer)，於PET基板上製作有機薄膜太陽能電池。本研究先比較電洞緩衝層(PEDOS:PSS)摻雜與未摻雜Glycerol對元件電流之影響，並改變主動層塗佈轉速，探討於不同轉速下元件效率之變化；再研究不同熱退火處理對元件之特性影響，接著比較單層與雙層電洞緩衝層(buffer layer)結構對元件之影響，並利用雙電洞緩衝層結構改善由G-PEDOT:PSS層所引起元件之漏電流以提升元件光電轉換效率(PCE)，同時改變雙電洞緩衝層之G-PEDOT:PSS旋轉塗佈轉速，探討其對元件效率影響。最後則改變主動層之有機材料對o-dichlorobenzene(DCB)之濃度與主動層之P3HT:PCBM之混合比例，研究其對元件光電轉換效率之影響。而本研究最佳結構為PET/ITO/PEDOT:PSS(2500 rpm/30s)/G-PEDOT:PSS(10000 rpm/30s)/P3HT:PCBM(1:1)/LiF/Al，P3HT:PCBM對DCB重量百分比為1.7%，以AM G1.5 100 mW/cm2模擬太陽光照射元件，利用KEITHLEY 2400量測元件之電流-電壓(I-V)特性，其光電轉換效率=4.5%，Voc=0.55，Isc=26.59mA/cm2。

關鍵字

小分子有機太陽能電池 ； 五環素 ； 熱處理 ； 高分子有機太陽能電池 ； 塑膠基板 ； 慢成長

並列摘要

This study is divided into two parts, one is small molecular organic solar cells and another one is flexible polymer solar cells. For the first part, In this study, organic solar cells (OSC) were fabricated by using pentacene and fullerene (C60). First, the 3,4-ethylenedioxythiophene-styrene sulfonate (PEDOT:PSS) were coated on indium-tin-oxide (ITO) substrates by spin-coating technique that can improve the surface roughness of ITO and increase the power conversion efficiency (PCE) from 0.49 to 0.58%. Next, glycerol with different concentrations was added into PEDOT:PSS to increase the conductivity of PEDOT:PSS that can increase the short current density of OSC. Thus the power conversion efficiency(PCE.) can be increased from 0.58 to 0.62% when glycerol concentration is 4%. Finally, if the OSC device was further put on the hot plate for annealing treatment, the absorption efficiency of C60 thin film was increased (as observed from the absorption spectra) and the pentacence/C60 interface properties can be improved. The annealing processes give rise to an increasing of PCE. from 0.62 to 0.84% with open voltage of 0.32 V and short-circuit current of 6.61 mA/cm2. The second part is flexible polymer solar cells, In this study, we mix two organic polymer materials, poly (3-hexylthiophene) (P3HT) and [6,6] - phenyl-C61 butyric acid methyl ester (PCBM), as the device for active absorption layer and use spin-coating on PET substrate to make flexible polymer solar cells. First, The effect of devices by compare with the doping and non doping of glycerol within hole buffer layer(PEDOS:PSS) of organic solar cells. And change the speed of spin coating of the active layer, examine the thickness effect for the devices I-V characteristics. Next, the effect of different annealing treatment to the device characteristics were first studied, and to compare the influence between single and double hole buffer layers to the device. The double hole buffer layer structure was used to improved the G-PEDOT: PSS layer which caused current leakage, and to further increase the power conversion efficiency (PCE). The PEDOT:PSS layer for spin coating was fixed at 2500 rpm and 30 seconds. The G-PEDOT:PSS spin coating speed was changed from 8000 to 12000 rpm for 30 seconds. When the G-PEDOT:PSS was at a slower speed, the G-PEDOT:PSS of DHBL was thicker the series resistance was larger, leading to a smaller short circuit current. When the spinning speed increased to 10000 rpm, a largest short circuit current density at 18.49 mA/cm2 was achieved. When the speed increased to 12000 rpm, due to the collecting ability of PEDOT:PSS is less than the G-PEDOT:PSS. The spin coating speeds for the double hole buffer layer were changed to explore its influence on the device. The best device producing conditions were at spin coating at 10000 rpm, the device characteristics were Voc=0.56V, Isc=18.49 mA/cm2, FF=33.2% and PCE.=3.44%. The organic material concentration of the active layer was then changed with the mixture ratio of o-dichlorobenzene (DCB) and P3HT:PCBM to study its effect on PCE. When weight percentage was 1.7% the largest short current density and efficiency was achieved. This is mainly because the exciton diffusion length and the thickness of the active layer were nearly the same at 118nm, in which the the current density and efficiency were higher compared to 2.0%. When the mixture ration of the active layer were respectively 1:0.5 and 1:2, the short circuit current density was not greater than 1:1. At ratio 1:1, the active material has the best absorption rate. In this study we have found that when the pre-annealing temperature is 120℃, the active material of P3HT and PCBM molecules elements arranged in organize, and increased the PCE to 2.02%. By the use of DBHL structure PET / ITO / PEDOT:PSS (2500rpm/30s) / G-PEDOT:PSS (10000rpm/30s) / P3HT:PCBM(1:1) / LiF(0.2nm) / Al(90nm ) to modify the leakage current of the device and to increase the PCE to 3.44%. The concentration of the active layer determines the spin coated thickness of the active layer. When the concentration of the active layer was 1.7% the best exciton diffusion length was achieved. When the ratio of P3HT:PCBM was 1:1, the active layer has a better light absorption, and can achieve the best component characteristics:PCE=4.5%, short circuit current=26.59 mA/cm2, open circuit voltage =0.55V, and F.F.=30.7%.

並列關鍵字

small organic solar cell ； pentacene ； annealing polymer solar cell ； PET ； slow growth

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