ESR spectroscopy for monitoring the photochemical and thermal degradation of conjugated polymers used as electron donor materials in organic bulk heterojunction solar cells

Frolova, Lyubov A.; Piven, N. P.; Susarova, Diana K.; Akkuratov, Alexander V.; Бабенко, С. Д.

doi:10.1039/c4cc08146c

Cited by 61 publications

(62 citation statements)

References 28 publications

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“…[8] The effect may deplete the initial power conversion efficiency (PCE) by as much as 20%-60%, [9] depending on the material system. [18] In light of these considerations, current state of the art envisions photovoltaic materials with elevated levels of photostability and high degree of purity and crystallinity, ideally free of radical-forming processing additives. [10] This intrinsic, light-driven degradation observation is thought to be mostly determined by material properties of the active layer and less due to interfaces and electrodes.…”

Section: Doi: 101002/aenm201700770mentioning

confidence: 99%

Burn‐in Free Nonfullerene‐Based Organic Solar Cells

Gasparini

Salvador

Strohm

et al. 2017

Advanced Energy Materials

216

212

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Organic solar cells that are free of burn‐in, the commonly observed rapid performance loss under light, are presented. The solar cells are based on poly(3‐hexylthiophene) (P3HT) with varying molecular weights and a nonfullerene acceptor (rhodanine‐benzothiadiazole‐coupled indacenodithiophene, IDTBR) and are fabricated in air. P3HT:IDTBR solar cells light‐soaked over the course of 2000 h lose about 5% of power conversion efficiency (PCE), in stark contrast to [6,6]‐Phenyl C61 butyric acid methyl ester (PCBM)‐based solar cells whose PCE shows a burn‐in that extends over several hundreds of hours and levels off at a loss of ≈34%. Replacing PCBM with IDTBR prevents short‐circuit current losses due to fullerene dimerization and inhibits disorder‐induced open‐circuit voltage losses, indicating a very robust device operation that is insensitive to defect states. Small losses in fill factor over time are proposed to originate from polymer or interface defects. Finally, the combination of enhanced efficiency and stability in P3HT:IDTBR increases the lifetime energy yield by more than a factor of 10 when compared with the same type of devices using a fullerene‐based acceptor instead.

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Section: Doi: 101002/aenm201700770mentioning

confidence: 99%

Burn‐in Free Nonfullerene‐Based Organic Solar Cells

Gasparini

Salvador

Strohm

et al. 2017

Advanced Energy Materials

216

212

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“…[10] On the other hand, amongstt he reportedh igh-performing materials, poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) [11] has been proven to show high stability in air. In some illustrative cases,c onsiderable scientific effort went into OPV systems based on promising materials that were later demonstrated to be inherently degraded upon exposure to air and light.…”

Section: Introductionmentioning

confidence: 99%

High‐Performing Polycarbazole Derivatives for Efficient Solution‐Processing of Organic Solar Cells in Air

et al. 2015

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The application of conjugated materials in organic photovoltaics (OPVs) is usually demonstrated in lab-scale spin-coated devices that are processed under controlled inert conditions. Although this is a necessary step to prove high efficiency, testing of promising materials in air should be done in the early stages of research to validate their real potential for low-cost, solution-processed, and large-scale OPVs. Also relevant for approaching commercialization needs is the use of printing techniques that are compatible with upscaling. Here, solution processing of organic solar cells based on three new poly(2,7-carbazole) derivatives is efficiently transferred, without significant losses, to air conditions and to several deposition methods using a simple device architecture. High efficiencies in the range between 5.0 % and 6.3 % are obtained in (rigid) spin-coated, doctor-bladed, and (flexible) slot-die-coated devices, which surpass the reference devices based on poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT). In contrast, inkjet printing does not provide reliable results with the presented polymers, which is attributed to their high molecular weight. When the device area in the best-performing system is increased from 9 mm(2) to 0.7 cm(2), the efficiency drops from 6.2 % to 5.0 %. Photocurrent mapping reveals inhomogeneous current generation derived from changes in the thickness of the active layer.

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“…35 These signals can be considered as a signature of the progress of the reaction, rather than of species participating in the reaction chain itself. Fig.…”

Section: Energy and Environmental Sciencementioning

confidence: 99%

“…Aging experiments were performed as described previously. 35 Three 400 W metal halogen lamps were employed as a light source. The power of the light intensity at the sample holder was about 80 mW cm…”

mentioning

confidence: 99%

Suppressing photooxidation of conjugated polymers and their blends with fullerenes through nickel chelates

Salvador

Gasparini

Perea

et al. 2017

Energy Environ. Sci.

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Conjugated polymer semiconductors offer unique advantages over conventional semiconductors but tend to suffer from electro-optic performance roll-off, mainly due to reduced photofastness. Here, we demonstrate that the commodity nickel chelate nickel(II) dibutyldithiocarbamate, Ni(dtc) 2 , effectively inhibits photooxidation across a wide range of prototypical p-conjugated polymer semiconductors and blends. The addition of 2-10 wt% of Ni(dtc) 2 increases the resilience of otherwise quickly photobleaching semiconducting thin films, even in the presence of detrimental, radical forming processing additives. Using electron spin resonance spectroscopy and sensitive oxygen probes, we found that Ni(dtc) 2 acts as a broadband stabilizer that inhibits both the formation of reactive radicals and singlet oxygen. The mechanism of stabilization is of sacrificial nature, but contains non-sacrificial contributions in polymers where singlet oxygen is a key driver of photooxidation. Ultrafast pump-probe spectroscopy reveals quenching of triplet excited states as the central mechanism of non-sacrificial stabilization. When introduced into the active layer of organic photovoltaic devices, Ni(dtc) 2 retards the short circuit current loss in air without affecting the sensitive morphology of bulk heterojunctions and without major sacrifices in semiconductor properties. Antioxidants based on nickel complexes thus constitute functional stabilizers for elucidating degradation mechanisms in organic semiconductors and represent a cost-effective route toward organic electronic appliances with extended longevity. Broader contextOrganic semiconductors based on conjugated polymers bear exceptional opportunities for many disruptive technologies, including light and power generation, sensor technology and electronic circuitry, which could potentially be realized in a sustainable fashion using highly efficient and low-cost approaches. However, conjugated polymers suffer from photo-oxidation-induced performance loss and need to be carefully encapsulated, compromising both applicability and cost benefits. In the present work, we introduce a nickel chelate, nickel(II) dibutyldithiocarbamate, as a universal antioxidant for increasing the longevity of conjugated polymers. We carried out a mechanistic study that quantitatively describes the stabilization of conjugated polymer moieties with technological relevance for OLEDs, OPVs and OFETs. We introduce for the first time a figure of merit (FOM) as a stabilization metric for antioxidants in conjugated polymers. This FOM serves likewise to distinguish between sacrificial and non-sacrificial protective mechanisms. We draw wide ranging conclusions that reflect on how conjugated polymer and polymer:fullerene blends photo-oxidize and how the underlying mechanisms can be significantly suppressed in the presence of nickel chelates. Finally, we demonstrate its beneficial use in a broad range of organic photovoltaic devices.

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ESR spectroscopy for monitoring the photochemical and thermal degradation of conjugated polymers used as electron donor materials in organic bulk heterojunction solar cells

Cited by 61 publications

References 28 publications

Burn‐in Free Nonfullerene‐Based Organic Solar Cells

Burn‐in Free Nonfullerene‐Based Organic Solar Cells

High‐Performing Polycarbazole Derivatives for Efficient Solution‐Processing of Organic Solar Cells in Air

Suppressing photooxidation of conjugated polymers and their blends with fullerenes through nickel chelates

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