The effect of oxygen induced degradation on charge carrier dynamics in P3HT:PCBM and Si-PCPDTBT:PCBM thin films and solar cells

Karuthedath, Safakath; Sauermann, Tobias; Egelhaaf, Hans‐Joachim; Wannemacher, Reinhold; Brabec, Christoph J.; Lüer, Larry

doi:10.1039/c4ta06719c

Cited by 45 publications

(45 citation statements)

References 30 publications

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“…Multiple degradation routes have been identifi ed in operating devices featuring P3HT:PCBM, which are related to the infl uence of ambient conditions (temperature, moisture, oxygen) in combination with light but also to material diffusion, and physical stress. [ 9,11,13,[15][16][17][18][19][20][21][22][23][24] More recently, the focus has been shifted toward correlating photochemical degradation reactions, such as photobleaching of the polymer, [ 9,25,26 ] fullerene dimerization, [ 27 ] cross-linking of photoactive components, [ 28 ] and interfacial reactions, with the observation of trap states [ 18,29,30 ] and charge carrier accumulation in the bulk and at the electrode interfaces of photovoltaic devices. [ 31,32 ] While elucidating the relationship between observed performance loss and cause is often diffi cult, the underlying degradation mechanisms depend critically on the active materials and the device geometry.…”

Section: Introductionmentioning

confidence: 99%

Water Ingress in Encapsulated Inverted Organic Solar Cells: Correlating Infrared Imaging and Photovoltaic Performance

Adams

Salvador

Lucera

et al. 2015

Advanced Energy Materials

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Understanding the degradation and failure mechanisms of organic photovoltaic devices is a key requirement for this technology to mature toward a reliable product. Here, an investigation on accelerated temperature and moisture long‐term stability testing (>20 000 h) of inverted and glass‐encapsulated poly(3‐hexylthiophene)/phenyl‐C61‐butyric acid methyl ester solar cells is presented. The degradation kinetics is analyzed using the Arrhenius model and the resulting activation energy for the diffusion of water is measured to be ≈43 kJ mol−1. Through comparison of electroluminescence imaging, lock‐in thermography, and photoluminescence mapping, the device performance is correlated with the loss of effective cell area and it is shown that the reaction of water at the hole extraction/active layer interface is likely to be the dominant cause for long‐term device failure. The diffusion of water through the packaged solar cell is described using classical diffusion theory. Based on an analytical solution of a simple diffusion model, the diffusion coefficient is estimated to be 4 × 10−12 m2 s−1. A shelf life of 100 000 h is anticipated at 65 °C/85% RH using a 9.3 cm wide protective adhesive rim. The findings of this study may inform strategies for predicting lifetimes of organic solar cells and modules based on local in situ tracking of moisture‐induced device performance loss using IR imaging.

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Section: Introductionmentioning

confidence: 99%

Water Ingress in Encapsulated Inverted Organic Solar Cells: Correlating Infrared Imaging and Photovoltaic Performance

Adams

Salvador

Lucera

et al. 2015

Advanced Energy Materials

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“…This is the case for organic solar cells, where it has been shown that an absorption loss of only a few percent may cause severe losses in electrical performance. 46 Organic solar cells are therefore an important test bed for evaluating the impact of promising stabilizing additives on the opto-electronic performance (rather than purely optical performance) of polymer semiconductors in devices, also with respect to the sensitive morphology. We fabricated organic solar cells with up to 4 wt% of Ni(dtc) 2 integrated into fullerene blends of the polymers PTB7, PTB7-Th and PCPDTBT (cf .…”

Section: View Article Onlinementioning

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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“…During the degradation process, trap states and defects are created due to different paths of degradation, e.g., photooxidation, diffusion of atoms, reorganization of BHJ, and many others. [32][33][34][35][36][37] Some of these trap states, close to the ITO/ZnO, could be filled up during the light-soaking illumination. 19,22 On the other hand, the trap states, close to the ZnO/P3HT:PCBM, could change the induced interfacial dipoles.…”

Section: Changes In Magnitude Of the Light-soaking Effect During The mentioning

confidence: 99%

“…[33][34][35] To investigate how the light-soaking effect and measurement procedure, which was applied, induce any additional photodegradation, one of the samples annealed at 130°C were measured only once in each measurement day and was not exposed to the illumination for LS. It minimized exposure of the solar cells to the light illumination and these measurements were called as never light soaked (NLS).…”

Section: Photodegradation Induced By Light-soaking Measurement Proceduresmentioning

confidence: 99%

Significance of light-soaking effect in proper analysis of degradation dynamics of organic solar cells

2016

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Abstract. One of the issues in the organic solar-cell technology that needs attention before mass production is its low long-term stability. These devices need often to be exposed to the light to improve their photovoltaic properties. This effect, known as light soaking, is the cause of challenges related to correct measurements and proper determination of the device lifetime. Lifetime determination and investigation of failure mechanisms of solar-cell devices require reliable measurement approaches. This paper presents the systematic studies on proper analysis of degradation dynamics of organic solar cells (OSCs) taking into account the light-soaking effect.Five groups of organic solar-cell annealed at various conditions (110°C to 170°C and nonannealed) were under investigation for 100 days. Measurement procedure for proper investigation of light-soaking effect is proposed. Solar-cell efficiency improvement, due to light-soaking effect, in range 8% to 27% was observed for as fabricated devices. After 100 days of study, the light soaking-related efficiency improvement increased up to over 100% of initial efficiency. Device lifetimes strongly depend on measurement methods, which were applied. Our results show the importance of taking into account the changes in magnitude of the light-soaking effect in measurements and degradation studies of OSCs. © The Authors. Published by SPIE under aCreative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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The effect of oxygen induced degradation on charge carrier dynamics in P3HT:PCBM and Si-PCPDTBT:PCBM thin films and solar cells

Cited by 45 publications

References 30 publications

Water Ingress in Encapsulated Inverted Organic Solar Cells: Correlating Infrared Imaging and Photovoltaic Performance

Water Ingress in Encapsulated Inverted Organic Solar Cells: Correlating Infrared Imaging and Photovoltaic Performance

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

Significance of light-soaking effect in proper analysis of degradation dynamics of organic solar cells

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