Degradation of Small‐Molecule‐Based OPV

Hermenau, Martin; Riede, Moritz; Leo, Karl

doi:10.1002/9781119942436.ch5

Cited by 6 publications

(3 citation statements)

References 58 publications

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“…The temperature at which solar cells begin to degrade is closely related to the glass transition temperature (T g ) of the component materials, with degradation beginning at temperatures above the lowest T g . For example, when the thermal stability of polymer:fullerene BHJs that use PPVs with high and low T g 's are directly compared, solar cells made from the low T g PPV degrade at room temperature while the high T g (138 °C) PPV solar cells do not .…”

Section: Intrinsic Degradationmentioning

confidence: 99%

Progress in Understanding Degradation Mechanisms and Improving Stability in Organic Photovoltaics

Mateker¹,

McGehee²

2016

Advanced Materials

368

337

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Understanding the degradation mechanisms of organic photovoltaics is particularly important, as they tend to degrade faster than their inorganic counterparts, such as silicon and cadmium telluride. An overview is provided here of the main degradation mechanisms that researchers have identified so far that cause extrinsic degradation from oxygen and water, intrinsic degradation in the dark, and photo-induced burn-in. In addition, it provides methods for researchers to identify these mechanisms in new materials and device structures to screen them more quickly for promising long-term performance. These general strategies will likely be helpful in other photovoltaic technologies that suffer from insufficient stability, such as perovskite solar cells. Finally, the most promising lifetime results are highlighted and recommendations to improve long-term performance are made. To prevent degradation from oxygen and water for sufficiently long time periods, OPVs will likely need to be encapsulated by barrier materials with lower permeation rates of oxygen and water than typical flexible substrate materials. To improve stability at operating temperatures, materials will likely require glass transition temperatures above 100 °C. Methods to prevent photo-induced burn-in are least understood, but recent research indicates that using pure materials with dense and ordered film morphologies can reduce the burn-in effect.

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Section: Intrinsic Degradationmentioning

confidence: 99%

Progress in Understanding Degradation Mechanisms and Improving Stability in Organic Photovoltaics

Mateker¹,

McGehee²

2016

Advanced Materials

368

337

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“…Research effort directed to improving the power conversion efficiency of organic solar cells (OSCs) has driven it toward and above 10%. − With such a promising initial efficiency, the long-term performance of OSCs also needs to be considered. , Extrapolated lifetimes of 2–3 years are reported in glass-on-glass encapsulated OSCs using the polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) blended with [6,6]-phenyl-C 60 -butyric acid methyl ester (PCBM), and lifetimes of 7–10 years are reported in encapsulated OSCs with the polymer poly[9′-hepta-decanyl-2,7-carbazole- alt -5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole) (PCDTBT) and fullerene [6,6]-phenyl-C 70 -butyric acid methyl ester (PC 71 BM). , When polymer solar cells made from PCDTBT and PC 71 BM are illuminated in an environment with less than 0.1 ppm oxygen and water, extrapolated lifetimes approaching 20 years are observed, which rivals the lifetimes observed in some evaporated small-molecule solar cells . Although such observations are promising, a more fundamental understanding of photodegradation processes that lead to short-term burn-in , and long-term performance loss is still needed.…”

Section: Introductionmentioning

confidence: 99%

Molecular Packing and Arrangement Govern the Photo-Oxidative Stability of Organic Photovoltaic Materials

et al. 2015

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For long-term performance chemically robust materials are desired for organic solar cells (OSCs). Illuminating neat films of OSC materials in air and tracking the rate of absorption loss, or photobleaching, can quickly screen a material's photo-chemical stability. In this report, we photobleach neat films of OSC materials including polymers, solution-processed oligomers, solution-processed small molecules, and vacuum-deposited small molecules. Across the materials we test, we observe photobleaching rates that span seven orders of magnitude. Furthermore, we find that the film morphology of any particular material impacts the observed photobleaching rate, and that amorphous films photobleach faster than crystalline ones. In an extreme case, films of amorphous rubrene photobleach at a rate 2500 times faster than polycrystalline films. When we compare density to photobleaching rate, we find that stability increases with density. We also investigate the relationship between backbone planarity and chemical reactivity. The polymer PBDTTPD is more photostable than its more twisted and less ordered furan derivitative, PBDFTPD. Finally, we relate our work to what is known about the chemical stability of structural polymers, organic pigments, and organic light emitting diode materials. For the highest chemical stability, planar materials that form dense, crystalline film morphologies should be designed for OSCs.

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“…In contrast to polymer:fullerene systems, the stability of OPVs that employ small molecule (SM) donors has attracted little attention so far. Early work investigated the influence of water and oxygen in zinc phthalocyanine‐based solar cells, but identified either the low work function electrodes and transport layers in the standard architecture or the C 60 acceptor as the main factors for device failure . While the poor stability of standard architecture devices in air is known, inverted architecture SM OPVs have been reported to be relatively stable, but no justification of this difference or underlying degradation mechanism has been reported …”

Section: Introductionmentioning

confidence: 99%

Energy Transfer to a Stable Donor Suppresses Degradation in Organic Solar Cells

Weu

Kumar

Butscher

et al. 2019

Adv Funct Materials

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Despite many advances toward improving the stability of organic photovoltaic devices, environmental degradation under ambient conditions remains a challenging obstacle for future application. Particularly conventional systems employing fullerene derivatives are prone to oxidize under illumination, limiting their applicability. Here, the environmental stability of the small molecule donor DRCN5T together with the fullerene acceptor PC 70 BM is reported. It is found that this system exhibits exceptional device stability, mainly due to almost constant short-circuit current. By employing ultrafast femtosecond transient absorption spectroscopy, this remarkable stability is attributed to two separate mechanisms: 1) DRCN5T exhibits high intrinsic resistance toward external factors, showing no signs of deterioration.2) The highly sensitive PC 70 BM is stabilized against degradation by the presence of DRCN5T through ultrafast, long-range energy transfer to the donor, rapidly quenching the fullerene excited states which are otherwise precursors for chemical oxidation. It is proposed that this photoprotective mechanism be utilized to improve the device stability of other systems, including nonfullerene acceptors and ternary blends.

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Degradation of Small‐Molecule‐Based OPV

Cited by 6 publications

References 58 publications

Progress in Understanding Degradation Mechanisms and Improving Stability in Organic Photovoltaics

Progress in Understanding Degradation Mechanisms and Improving Stability in Organic Photovoltaics

Molecular Packing and Arrangement Govern the Photo-Oxidative Stability of Organic Photovoltaic Materials

Energy Transfer to a Stable Donor Suppresses Degradation in Organic Solar Cells

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