Analysis of the degradation mechanism of ITO-free organic solar cells under UV radiation

Sapkota, Subarna B.; Fischer, Martin; Zimmermann, Birger; Würfel, Uli

doi:10.1016/j.solmat.2013.10.021

Cited by 31 publications

(24 citation statements)

References 35 publications

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“…[5,6] Thealuminumcathode layers are fabricated by using acustomized R2R DC magnetron sputter coater purchased from Semicore Equipment (Figure 1b). This machine passes the flexible substrate around ac ylindrical drum where it is exposed to three consecutive deposition zones from individually controlled targets.T his allows for the ability to deposit multiple materials in as ingle run, enabling, for instance, single passf abrication of emergingm aterials in the R2R fabrication space such as indium-tin oxide (ITO)-metal-ITO (IMI) [27] conductive plastic anodes or chromium-aluminumchromium [9] cathode film structures.T he choice of magnetron sputtering for cathode depositioni ns tandard device architectures is divergentf rom the majority of previous efforts in the large-scale fabrication domain. Here we utilize the R2R sputter coater to examine the feasibility of depositing aluminumc athodes directly onto organic layers using an industrial-scale process.…”

Section: Resultsmentioning

confidence: 99%

“…[5] In particular, there is ad istinct lack of printable electrode materials,w ith silver inks currently employed to create the cathode in the bulk of reported printed OPV structures.T hough this approachh as produced single modules with efficiencies exceeding3%a nd has allowed upscaled manufacture to installationsp roducing more than 10 kV by linking upwards of 100 000 cells with ef-ficiencies of 1.5 %i ns eries, [6] moving from thermally evaporated cathode deposition on the small scale to printed cathode depositiono nt he R2R scale remains as ignificant challenge. [7] Sputtering of metal contacts has provent ob easuccessful route for massp roduction of liquid-crystal displays, [8] and presentss ome uniquea dvantages compared to printable cathodes.T he technology is compatible with large-area substrates,c an deposit ar ange of materials including pure metals,a lloys,a nd oxide semiconductors, [9,10] and does not suffer wettabilityi ssues,r esulting in compatibilityw ith aw ide range of device architectures.F urthermore,s puttering…”

Section: Introductionmentioning

confidence: 99%

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Roll‐to‐Roll Sputter Coating of Aluminum Cathodes for Large‐Scale Fabrication of Organic Photovoltaic Devices

et al. 2015

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We report the demonstration of sputter‐coated aluminum contacts directly onto P3HT:PCBM organic photovoltaic devices using a R2R process without detrimentally influencing the performance of the devices. The final sputtered devices do not require any protective buffer layers to produce efficient performance. Depth profiling analysis of sputtered films using X‐ray photoelectron spectroscopy (XPS) indicated the presence of a 5–6 nm insulating oxide layer generated at the cathode interface for all sputtering target power densities greater than 1.4 W cm−2. The aluminum penetration into the P3HT:PCBM film was found to be consistent with the depth of this oxide layer, suggesting that aluminum penetration into the organic film is not the primary reason for performance limitations in sputtered devices. Introduction of thermally evaporated aluminum buffer layers prior to deposition of sputtered aluminum cathodes demonstrated that the performance of devices after annealing matched those of reference devices prepared with no sputtering for a buffer layer thickness of only 20 nm. Further analysis of the device J‐‐V curves revealed an S‐shaped kink prior to annealing, indicating that the major reason for the poor performance in sputtered devices was the introduction of a charge extraction barrier at the cathode, which was subsequently removed upon annealing. Rigorous removal of oxygen from the sputtering chamber prior to aluminum deposition onto the P3HT:PCBM active layer was subsequently observed to produce a device with an efficiency close to that of the thermally evaporated reference device without the requirement for evaporated buffer layers. The results presented here highlight a pathway towards an alternative R2R cathode fabrication technique that allows the highly efficient aluminum cathodes employed in small‐scale devices to be transferred onto large‐scale, flexible, and low‐cost R2R printed organic electronic devices.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Roll‐to‐Roll Sputter Coating of Aluminum Cathodes for Large‐Scale Fabrication of Organic Photovoltaic Devices

et al. 2015

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“…[ 35,37 ] Moreover, it was recently demonstrated that UV light is also detrimental for PEDOT:PSS conductivity. [ 58 ] Nevertheless, despite the multitude of reported aging mechanisms of PEDOT:PSS, there have been instances where PEDOT:PSS was reported not to affect the aging rate of the devices, [ 32 ] or even to improve the stability when compared to metal oxides. [ 26 ] Thus, in order to understand this controversy, the literature data was analyzed with regard to the use of PEDOT:PSS in the devices, as shown in Figure 6 …”

Section: Pedot:pss Studiesmentioning

confidence: 99%

Lifetime of Organic Photovoltaics: Status and Predictions

Gevorgyan

Madsen

Roth

et al. 2015

Advanced Energy Materials

134

124

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performance level, especially when considering large-scale mass-produced modules, is predicted to be signifi cantly lower. [ 8 ] Nevertheless, based on recent advances in the upscaling of OPV manufacture [9][10][11][12] it is reasonable to assume that the mass production of modules with an effi ciency of more than 5% is an achievable target today. Durability of OPV is however yet to be proven and demonstrated.Due to core architectural differences between OPV and inorganic technologies [ 13 ] the established testing standards of the latter are not applicable to the former. [ 1 ] Hence, for many years the stability testing of OPV has primarily been based on customized procedures that vary from one laboratory to another, generating incomparable data. [ 14 ] Moreover, due to the complexity of the OPV device architectures [ 15 ] and a multitude of aging mechanisms taking place at the same time [ 16 ] the aging curve of OPV often takes a complex shape, which is diffi cult to model, [ 14,17 ] thus making the identifi cation of a practical operational lifetime diffi cult or impossible. [ 18 ] As a result, even with a multitude of reported review articles discussing OPV stability [ 16,[19][20][21][22][23][24] at hand, it is still challenging to identify where the technology stands in terms of lifetime. To address this it is necessary to create a yardstick -a generic marker that allows accurate rating and comparison of the lifetime for OPV, and thus enabling the gauging of progress over time. An additional complication that has arisen due to the signifi cant improvements in OPV stability and durability in recent years is that the determination of OPV lifetimes has become an impractically long process, and establishing markers for both accelerated and real operational test conditions (if successful) would allow developing a prediction tool that could speed up the stability testing process and tackle this issue.The groundwork towards creating such a marker was laid in 2011 at the International Summit on OPV Stability (ISOS) where the ISOS testing guidelines were decided upon and described for OPV technologies. [ 18 ] These guidelines were primarily aimed at harmonizing testing procedures among different laboratories by offering a set of indoor and outdoor tests with controlled conditions. This has helped to reduce variations in the reported results, making the aging studies of different laboratories more comparable. [ 25 ] While the ISOS tests harmonized the test conditions, the questions of how to generically determine the lifetime from aging curves of diverse shapes, and how to build a technique for predicting the lifetime based on accelerated tests remained.The results of a meta-analysis conducted on organic photovoltaics (OPV) lifetime data reported in the literature is presented through the compilation of an extensive OPV lifetime database based on a large number of articles, followed by analysis of the large body of data. We fully reveal the progress of reported OPV lifetimes. Furthermore, a generic lifetime marker has...

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“…It can be speculated that the dominating ageing mechanisms possibly originate from the top PEDOT:PSS layer. The latter is well known to be rather sensitive toward environmental factors and especially the UV light and since it was positioned above the V 2 O 5 , its ageing rate was not altered by the presence of V 2 O 5 in the architecture. Therefore, it is expected that the complete elimination of the PEDOT:PSS layer or improvement of its stability will significantly improve the overall intrinsic stability of the devices and even a simple cheap encapsulation may lead to device lifetimes that will enable not only indoor applications, but also sustainable energy production in outdoor conditions.…”

Section: Operational Lifetime and Encapsulationmentioning

confidence: 99%

Slot‐Die‐Coated V₂O₅ as Hole Transport Layer for Flexible Organic Solar Cells and Optoelectronic Devices

et al. 2016

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Vanadium pentoxide has been proposed as a good alternative hole transport layer for improving device lifetime of organic photovoltaics. The article presents a study on the optimization of slot-diecoated vanadium oxide films produced with a roll coating machine with the aim of achieving scalable organic solar cells and photo-detectors with improved performance. The effect of different diluents on the electrical properties of the vanadium oxide films is investigated, and methodologies for efficient interfacing of the anode are studied. Furthermore, the lifetime of the cells with incorporated vanadium oxide is investigated employing different encapsulation methods. Finally, an application of the manufactured scalable devices in proximity sensors is demonstrated using a 3D-printed scaffold.

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Analysis of the degradation mechanism of ITO-free organic solar cells under UV radiation

Cited by 31 publications

References 35 publications

Roll‐to‐Roll Sputter Coating of Aluminum Cathodes for Large‐Scale Fabrication of Organic Photovoltaic Devices

Roll‐to‐Roll Sputter Coating of Aluminum Cathodes for Large‐Scale Fabrication of Organic Photovoltaic Devices

Lifetime of Organic Photovoltaics: Status and Predictions

Slot‐Die‐Coated V₂O₅ as Hole Transport Layer for Flexible Organic Solar Cells and Optoelectronic Devices

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Analysis of the degradation mechanism of ITO-free organic solar cells under UV radiation

Cited by 31 publications

References 35 publications

Roll‐to‐Roll Sputter Coating of Aluminum Cathodes for Large‐Scale Fabrication of Organic Photovoltaic Devices

Roll‐to‐Roll Sputter Coating of Aluminum Cathodes for Large‐Scale Fabrication of Organic Photovoltaic Devices

Lifetime of Organic Photovoltaics: Status and Predictions

Slot‐Die‐Coated V2O5 as Hole Transport Layer for Flexible Organic Solar Cells and Optoelectronic Devices

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Slot‐Die‐Coated V₂O₅ as Hole Transport Layer for Flexible Organic Solar Cells and Optoelectronic Devices