Flexible PTB7:PC71BM bulk heterojunction solar cells with a LiF buffer layer

Yanagidate, Tatsuki; Fujii, Shunjiro; Ohzeki, Masaya; Yanagi, Yousuke; Arai, Yasuhiko; Okukawa, Takanori; Yoshida, Akira; Kataura, Hiromichi; Nishioka, Yasushiro

doi:10.7567/jjap.53.02be05

Cited by 29 publications

(20 citation statements)

References 47 publications

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“…[ 9,10 ] The fact that V oc and J sc do not change with aging, suggests that the V 2 O 5 hole collection layer is at least partially encapsulating the active layer from irreversible degradation. [ 32 ] We attribute both the stability of the device architecture as well as the recovery of the J -V characteristics after aging to the redox properties of V 2 O 5 .…”

Section: Introductionmentioning

confidence: 96%

Loss Mechanisms in High Efficiency Polymer Solar Cells

MacKenzie

Balderrama

Schmeisser

et al. 2015

Advanced Energy Materials

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[ 6 ] and phenyl-C71-butyric acid methyl ester (PC 70 BM). [ 2 , 7 ] Despite promising results, the performance of PTB7:PC 70 BM solar cells is limited by the thin active layer, [ 3 ] carrier selectivity at the contacts, [ 8 ] and rapid degradation of the active layer and contacts caused by exposure to ambient oxygen [9][10][11] and water vapor. [ 12 ] Although inverted solar cell architectures have demonstrated high effi ciencies combined with relatively good stability, age-induced performance loss in high performance PTB7 solar cell architectures [ 2 ] has been reported, and the mechanisms are currently not well understood.Identifying the origins of performance loss in solar cells is challenging because it involves differentiating between interfacial phenomena and bulk properties. [ 13 ] Frequency resolved optoelectronic techniques such as impedance spectroscopy [ 14 ] and intensity modulated photocurrent spectroscopy (IMPS) [ 15 ] are useful in discriminating between electronic processes in the active layer and at contact interfaces, and correlating these with device performance. In this work, we combine these techniques with device modeling to identify key loss processes and aging mechanisms in state-of-the-art PTB7-based inverted solar cells incorporating a V 2 O 5 hole transport layer. After prolonged exposure to ambient conditions no change in the open circuit voltage ( V oc ) or short circuit current density ( J sc ) was observed. An s-shape is initially observed in the current density -voltage ( J -V) characteristic, which can be reversed by cycling through the J -V curve under illumination. Subsequently, a small drop in the fi ll factor (FF) from the original value of 0.7 to 0.61 was observed. With impedance spectroscopy, we demonstrate that changes to the device interfaces are completely reversible, and that performance losses related to the FF are due to degradation of the organic active layer. The IMPS analysis reveals age-related trap formation in the active layer. Interestingly, the high density of traps does not appear to have a signifi cant effect on performance. We attribute this phenomenon to slow carrier thermalization times. ResultsThe device structure is depicted in Figure 1 a. The PTB7:PC 70 BM active layer was sandwiched between an Indium tin oxide (ITO)/ poly [(9,9-bis(3-( N , N -dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfl uorene)] (PFN) [ 16 ] electron extracting contact

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Section: Introductionmentioning

confidence: 96%

Loss Mechanisms in High Efficiency Polymer Solar Cells

MacKenzie

Balderrama

Schmeisser

et al. 2015

Advanced Energy Materials

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“…The cells were fabricated using a p-type semiconductor, poly [[4,8- , an n-type semiconductor, [6,6]-phenyl-C71-butyric-acid-methyl-ester (PC 71 BM), and a lithium fluoride (LiF) inserted Al cathode on an indium tin oxide (ITO) coated glass substrate. These promising results inspired many recent studies on BHJ solar cells based on PTB7:PC 71 BM, and various techniques were proposed to further improve the performance of the BHJ solar cells [22][23][24][25][26][27][28][29][30][31][32][33]. [40,41].…”

Section: Introductionmentioning

confidence: 76%

“…2. The solar cells were fabricated based on the procedures previously described [32,33,37]. The devices were fabricated on an ITO-coated glass substrate with a sheet resistance of 10 Ω/sq (Techno Print) and a thickness of 150 nm with electrode patterns.…”

Section: Fabrication Of Bhj Solar Cellsmentioning

confidence: 99%

Bulk-heterojunction Solar Cells Based on Ternary Blend Active Layers of PTB7, PC61BM, and PC71BM

Qiu

Kiriishi

Hashiba

et al. 2015

J. Photopol. Sci. Technol.

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Bulk-heterojunction solar cells were fabricated using ternary blend dichlorobenzene solutions of poly [4,8-bis[(2-ethylhexyl)]-phenyl-C61-butyric acid methyl ester (PC 61 BM):[6,6]-phenyl C71 butyric acid methyl ester (PC 71 BM) with different weight ratios between PC 61 BM and PC 71 BM. In all the solar cells, the overall weight ratio of polymer to fullerene was maintained at 1:1.5, while the composition of the fullerene component (PC 61 BM:PC 71 BM) was varied. The ultraviolet-visible absorption spectra of these ternary blend films showed that the photon absorptions at wavelengths between 300 and 800 nm continuously decreased with the increase of the PC 61 BM weight fraction in the PC 61 BM and PC 71 BM total weight. The measurement results of the solar cell performance showed that the open-circuit voltage notably increased for PC 61 BM weight fractions between 10% and 90%, while it decreased at 100%. The short-circuit current showed the most significant increase in the PC 61 BM weight fraction range between 50% and 60%. A power conversion efficiency of 3.4% was achieved when the PC 61 BM weight fraction was between 50% and 60%. These results may suggest that the transport of the photoexcited electrons between the cathode and the PC 61 BM/PC 71 BM nanodomains was enhanced.

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“…2. The BHJ solar cells were fabricated according to the procedures previously described [32,33]. The devices were fabricated on ITO-coated glass…”

Section: Fabrication Of Bhj Solar Cellsmentioning

confidence: 99%

Organic Solar Cells Based on Ternary Blend Active Layer of Two Donors PTB7, P3HT and Accepter PC61BM

Ohori

Hoashi

Yanagi

et al. 2014

J. Photopol. Sci. Technol.

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Bulk-heterojunction solar cells were fabricated using ternary blend dichlorobenzene solutions of poly [4,8-bis[(2-ethylhexyl)poly(3-hexylthiophene)(P3HT):[6,6]-phenyl-C 61 -butyric acid methyl ester (PC 61 BM) with different weight ratios between PTB7 and P3HT on an indium-tin-oxide-coated glass substrate. The UV-vis absorption spectra of these ternary blend films show that the photon absorptions at the wave lengths of 500 and 700 nm can be adjusted depending on the P3HT polymer weight fraction in the PTB7 and P3HT total weight. The measurement results of the solar cell performance showed that the open circuit voltage V oc continuously increased from 0.62 to 0.79 V as the P3HT fraction increased from 0 to 20 %, while it gradually decreased above 30%. The short circuit current J sc slightly decreased from 10.4 to 9.0 A/cm 2 up to 20%, and it suddenly dropped above 30%. The power conversion efficiency of 4% decreased to 1.8% when the P3HT fraction increased to 30%. These results may suggest that the transports of photo excited electrons and holes between the PTB7 nano domains and P3HT nano domains are disturbed by the differences between the HOMO and LUMO levels of the PTB7 and P3HT.

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Flexible PTB7:PC₇₁BM bulk heterojunction solar cells with a LiF buffer layer

Cited by 29 publications

References 47 publications

Loss Mechanisms in High Efficiency Polymer Solar Cells

Loss Mechanisms in High Efficiency Polymer Solar Cells

Bulk-heterojunction Solar Cells Based on Ternary Blend Active Layers of PTB7, PC<sub>61</sub>BM, and PC<sub>71</sub>BM

Organic Solar Cells Based on Ternary Blend Active Layer of Two Donors PTB7, P3HT and Accepter PC61BM

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