Influence of hole extraction efficiency on the performance and stability of organic solar Cells

Ecker, Bernhard; Posdorfer, J.; Hauff, Elizabeth von

doi:10.1016/j.solmat.2013.04.019

Cited by 31 publications

(34 citation statements)

References 26 publications

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“…[29][30][31] Interesting, we also note that when the aged device is successively cycled through the J -V curve under illumination, the s-shape is reduced (Figure 2, gray symbols) and after 100 cycles the J -V curve fully recovers, except for the drop in FF. This suggests that J -V cycling under light exposure reduces the height of an extraction barrier within the device.…”

Section: Introductionmentioning

confidence: 77%

“…Impedance spectroscopy has previously been widely applied to study recombination, transport, and carrier extraction barriers in organic solar cells. [ 24,30,31,[38][39][40] Measurements were performed under illumination on the pristine device (fresh), and on the degraded device after the s-shape had been eliminated from the J -V (aged). (black) and after (blue) aging.…”

Section: Introductionmentioning

confidence: 99%

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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: 77%

Section: Introductionmentioning

confidence: 99%

Loss Mechanisms in High Efficiency Polymer Solar Cells

MacKenzie

Balderrama

Schmeisser

et al. 2015

Advanced Energy Materials

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“…As shown in Table 2, the solar cells dark stored in dry N 2 and vacuum shows higher capacitance values compared to the solar cell dark stored in dry air. The higher chemical capacitance causes more charge accumulation at the interfaces and reduces the hole extraction efficiency, leading to the overall decrease in the performance of perovskite solar cells dark stored in dry N 2 and vacuum [75].…”

Section: Impedance Measurementsmentioning

confidence: 99%

Atmospheric effects on the photovoltaic performance of hybrid perovskite solar cells

Sheikh

Bera

Haque

et al. 2015

Solar Energy Materials and Solar Cells

122

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“…To further investigate the photovoltaic parameters of tandem devices with different interconnecting layer combinations, we performed the electrical impedance spectrum measurements which enabled us to monitor the specific electrical properties of the interfaces [23,[31][32][33][34]. Figure 7 shows the Cole-Cole plot (the imaginary resistance, Zim over the real resistance, Zre) of tandem devices with different interconnecting layers in the dark.…”

Section: Results and Analysismentioning

confidence: 99%