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We show enhanced efficiency and stability of a high performance organic solar cell (OPV) when the work-function of the hole collecting indium-tin oxide (ITO) contact, modified with a solution-processed nickel oxide (NiOx) hole-transport layer (HTL), is matched to the ionization potential of the donor material in a bulk-heterojunction solar cell. Addition of the NiOx HTL to the hole collecting contact results in a power conversion efficiency (PCE) of 6.7%, which is a 17.3% net increase in performance over the 5.7% PCE achieved with a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HTL on ITO. The impact of these NiOx films is evaluated through optical and electronic measurements as well as device modeling. The valence and conduction band energies for the NiOx HTL are characterized in detail through photoelectron spectroscopy studies while spectroscopic ellipsometry is used to characterize the optical properties. Oxygen plasma treatment of the NiOx HTL is shown to provide superior contact properties by increasing the ITO/NiOx contact work-function by 500 meV. Enhancement of device performance is attributed to reduction of the band edge energy offset at the ITO/NiOx interface with the poly(N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothidiazole) (PCDTBT):[6,6]-phenyl-C61 butyric acid methyl ester PCBM and [6,6]-phenyl-C71 butyric acid methyl ester (PC70BM) active layer. A high work-function hole collecting contact is therefore the appropriate choice for high ionization potential donor materials in order to maximize OPV performance.

The inverted organic photovoltaic (OPV) device architecture represents an important advancement due to the relative environmental stability of the electron transport layer (ETL) and hole-collecting contact. We investigated the initial and long-term behavior of inverted devices to identify changes taking place at the Ag hole-collecting contact. We show that efficient hole collection can be obtained after modifying the Ag contact by thermal annealing, long-term exposure to ambient atmosphere, or employing a high work function organic hole-transport layer (HTL). We find that whether or not the device employs an organic HTL, degradation of the photocurrent initially follows a simple exponential decay. After prolonged illumination (>500 h), devices with an organic HTL fail catastrophically due to a precipitous drop in photocurrent. Based on evidence for pinhole-induced degradation observed in photocurrent maps, we propose a nucleation and island growth mechanism and a model for the photocurrent behavior employing a modified Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation. Devices that do not contain an HTL appear to degrade by a mechanism other than pinhole ingress resulting in a more uniform degradation of the photocurrent across the active area.

Device function in organic electronics is critically governed by the transport of charge across interfaces of dissimilar materials. Accurate measurements of energy level positions in organic electronic devices are therefore necessary for assessing the viability of new materials and optimizing device performance. In contrast to established methods that are used in solution or vacuum environments, here we combine Kelvin probe measurements performed in ambient environments to obtain work function values with photoelectron spectroscopy in air to obtain ionization potential, so that a complete energy level diagram for organic semiconductors can be determined. We apply this new approach to study commonly used electron donor and acceptor materials in organic photovoltaics (OPV), including poly(3-hexylthiophene) (P3HT), [6,6]-phenyl C61 butyric acid methyl ester (PCBM), and ZnO, as well as examine new materials. Band alignments across the entire OPV devices are constructed and compared with actual device performance. The ability to determine interfacial electronic properties in the devices enables us to answer the outstanding question: why previous attempts to make OPV devices using 6,13-bis(triisopropylsilylethynyl) (TIPS)-pentacene as the electron donor were not successful.

We present strategies to improve low open-circuit voltage (Voc) for ZnO-poly(3-hexylthiophene) (P3HT) photovoltaic devices, which are typically ≤0.4 V, but vary among different reports. One factor affecting Voc variability is the ZnO bandgap (Eg), which depends on detailed processing conditions. By decreasing the pyrolysis temperature of sol-gel ZnO films, we increased the ZnO Eg by 0.14 eV and Voc of corresponding bilayer devices by 0.1 V. This is understood as increased donor-acceptor energy-level offset. Next, we demonstrate significant enhancement in Voc by depositing conformal amorphous TiOx films at the surface of planar ZnO films and ZnO nanorod arrays using a spin-coating method. The TiOx coatings monotonically increased Voc from 0.4 to 0.8 V for devices with increasing TiOx thicknesses from 0 to ≥50 Å. Dark current-voltage measurement reveals that the TiOx coating significantly decreases the reverse-bias current density, leading to an improvement in Voc, in excellent agreement with predictions from the modified ideal diode equation. This is consistent with passivation of ZnO surface defects by TiOx. In short, by varying the solution processing conditions, we modify the bulk and interfacial properties of the metal oxide acceptor, thus leading to systematic improvement in open-circuit voltage.

As organic photovoltaic effi ciencies steadily improve, understanding degradation pathways becomes increasingly important. In this paper, the stability under prolonged illumination of a prototypical polymer:fullerene active layer is studied without the complications introduced by additional layers and interfaces in complete devices. Combining contactless photoconductivity with spectroscopy, structural characterization at the molecular and fi lm level, and quantum chemical calculations, the mechanism of photoinduced degradation in bulk heterojunctions of poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) is studied. Bare fi lms are subjected to four conditions for 1000 h with either constant illumination or dark and either ambient or inert atmosphere. All samples are found to be intrinsically stable for 1000 + h under inert conditions, in contrast to complete devices. While PCBM stabilizes P3HT fi lms exposed to air, its fullerene cage is found to undergo a series of oxidations that are responsible for the deterioration of the photoconductivity of the material. Quantum chemical calculations show that PCBM oxides have deeper LUMO levels than pristine PCBM and therefore act as traps for electrons in the PCBM domains.

Organic and hybrid (organic/inorganic) solar cells are an attractive alternative to traditional silicon-based photovoltaics due to low-temperature, solution-based processing and the potential for rapid, easily scalable manufacturing. Using oxide semiconductors, instead of fullerenes, as the electron acceptor and transporter in hybrid solar cells has the added advantages of better environmental stability, higher electron mobility, and the ability to engineer interfacial band offsets and hence the photovoltage. Further improvements to this structure can be made by using metal oxide nanostructures to increase heterojunction areas, similar to bulk heterojunction organic photovoltaics. However, compared to all-organic solar cells, these hybrid devices produce far lower photocurrent, making improvement of the photocurrent the highest priority. This points to a less than optimized polymer/metal oxide interface for carrier separation. In this article, we summarize recent work on examining the polymer structure, electron transfer, and recombination at the polythiophene-ZnO interface in hybrid solar cells. Additionally, the impact of chemical modification at the donor-acceptor interface on the device characteristics is reviewed.

The integration of zinc oxide (ZnO) and cadmium sulfide (CdS) has shown promise in applications such as sensing and photovoltaics. We describe here a room temperature, aqueous synthetic strategy to selectively grow nanocrystalline CdS on ZnO. In particular, we describe an experimentally simple process that selectively grows a conformal nanocrystalline coating only 1 nanocrystal (10−20 nm) thick on planar and three-dimensional extended ZnO structures. We explore the synthesis, characterization, and mechanisms involved in the formation of this composite material, and we demonstrate a promising optical response from these composite structures that may prove valuable for future optoelectronic applications.

Hybrid inorganic oxide/conjugated polymer photovoltaic devices using ZnO nanorod arrays (NRAs) instead of planar films as the electron-transport layer exhibit significant improvements in performance that have been attributed to increased heterojunction surface area, although the relationship has not been quantitatively established. Here, we independently measure the surface area of ZnO NRAs and quantify its effect on the performance of ZnO NRA/poly(3-hexylthiophene) (P3HT) photovoltaic devices. We find that a device utilizing a vertically aligned 180 nm ZnO NRA exhibits an ∼2.7× enhancement in the short-circuit current compared with that of a bilayer device, in excellent agreement with the increase in surface area. In addition, we show that a subtle difference in the NRA morphology can impact P3HT crystallinity in the photoactive region. Improved P3HT crystallinity leads to an ∼25% enhancement in the short-circuit current for devices with the same surface area. On the basis of these findings, we modify th...

Solution-processable small molecules have attractive features for application in photovoltaic cells. They offer the facile processing associated with polymers, yet are easier to synthesize and purify, are monodisperse, and typically show higher charge carrier mobilities. Recent progress in solution-processable small molecule blends has yielded photovoltaic cells with efficiencies exceeding 1%. This article reviews progress in this nascent field and discusses the requirements imposed by the need for charge separation within an interpenetrating network, energy level tuning for light absorption and voltage output, and processing techniques to achieve phase separation on excitonic length scales. Design criteria for next-generation materials are provided.

A novel, easy processable n-type polythiophene derivative poly(3-cyano-4-hexylthiophene) (P3CN4HT) was synthesized and characterized with different spectroscopic techniques such as 1H NMR, size exclusion chromatography, Fourier transformed infrared spectroscopy (FT-IR), UV−vis, photoluminescence, and cyclic voltammetry. P3CN4HT is very soluble in common organic solvents (tetrahydrofyran, chloroform) and has high electron affinity. Systematic photoluminescence measurements were used to characterize several electron donating polymers such as poly(2-methoxy-5-[3‘,7‘-dimethyloctyloxy]-p-phenylene vinylene) (MDMO-PPV), regioregular poly(3-octylthiophene) (P3OT), and poly(4,4‘-dihexylcyclopentadithiophene) (PCPDT). When P3CN4HT was employed in blends as the electron acceptor, we observed complete photoluminescence quenching for both MDMO-PPV:P3CN4HT and P3OT:P3CN4HT mixtures. Preliminary photovoltaic measurements demonstrated power conversion efficiency as high as 0.014% for the MDMO-PPV:P3CN4HT blend without a...

Multilayer heterojunction photovoltaic cells were fabricated using a solution processable pentacene derivative as the donor layer. Upon annealing of these devices, the open circuit voltage was found to gradually increase with temperature up to 265 °C. Further improvement in the photovoltaic performance was achieved with the incorporation of mobile ions into the donor material for concentrations of lithium triflate up to 1.4 mg/ml. Finally, after introducing an exciton blocking layer, an optimized white-light (100 mW/cm2) power conversion efficiency of 0.52% was achieved.

Solvent evaporation rate, ionic conductivity, and photovoltaic response were used to compare a traditional organic liquid electrolyte to a gel electrolyte and a nanocomposite gel electrolyte consisting of poly(vinylidenefluoride- co -hexafluoropropylene) (PVdF-HFP) and 12.5 wt.% synthetic layered silicate particles. The addition of layered silicate nanoparticles to the pure gel electrolyte markedly increased solvent retention and improved mechanical strength. The nanocomposite gel electrolyte had a conductivity of 2.6 × 10 −3 S/cm and a power conversion efficiency matching that of the liquid electrolyte.

We studied the effects of postfabrication annealing on heterojunction photovoltaic cells made from vacuum deposited pentacene and C60. The maximum power conversion efficiency under 115mW∕cm2 illumination increases from 0.45% to 1.07% after annealing the cells at 200°C. The increased performance is a result of better molecular ordering, which leads to an increased shunt resistance and built-in potential.

Trabajo presentado como comunicación al "Reliability of Photovoltaic Cells, Modules, Components, and Systems V" celebrada del 13 al 16 de Agosto del 2012 en San Diego (USA).-- et al., This work is part of the inter-laboratory collaboration to study the stability of seven distinct sets of state-of-the-art organic photovoltaic (OPVs) devices prepared by leading research laboratories. All devices have been shipped to and degraded at the Danish Technical University (DTU, formerly RISO-DTU) up to 1830 hours in accordance with established ISOS-3 protocols under defined illumination conditions. In this work we present a summary of the degradation response observed for the NREL sample, an inverted OPV of the type ITO/ZnO/P3HT:PCBM/PEDOT:PSS/Ag/Al, under full sun stability test. The results reported from the combination of the different characterization techniques results in a proposed degradation mechanism. The final conclusion is that the failure of the photovoltaic response of the device is mainly due to the degradation of the electrodes and not to the active materials of the solar cell. © (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Trabajo presentado como comunicación al "XIII Organic Photovoltaics" celebrado del 14 al 16 de Agosto del 2012 en San Diego (USA).-- et al., Seven distinct sets (n > 12) of state of the art organic photovoltaic devices were prepared by leading research laboratories in a collaboration planned at the Third International Summit on Organic Photovoltaic Stability (ISOS-3). All devices were shipped to DTU and characterized simultaneously up to 1830 h in accordance with established ISOS-3 protocols under three distinct illumination conditions: accelerated full sun simulation; low level indoor fluorescent lighting; and dark storage with daily measurement under full sun simulation. Three nominally identical devices were used in each experiment both to provide an assessment of the homogeneity of the samples and to distribute samples for a variety of post soaking analytical measurements at six distinct laboratories enabling comparison at various stages in the degradation of the devices. Characterization includes current-voltage curves, light beam induced current (LBIC) imaging, dark lock-in thermography (DLIT), photoluminescence (PL), electroluminescence (EL), in situ incident photon-to-electron conversion efficiency (IPCE), time of flight secondary ion mass spectrometry (TOF-SIMS), cross sectional electron microscopy (SEM), UV visible spectroscopy, fluorescence microscopy, and atomic force microscopy (AFM). Over 100 devices with more than 300 cells were used in the study. We present here design of the device sets, results both on individual devices and uniformity of device sets from the wide range of characterization methods applied at different stages of aging under the three illumination conditions. We will discuss how these data can help elucidate the degradation mechanisms as well as the benefits and challenges associated with the unprecedented size of the collaboration.

The present work is the fourth (and final) contribution to an inter-laboratory collaboration that was planned at the 3rd International Summit on Organic Photovoltaic Stability (ISOS-3). The collaboration involved six laboratories capable of producing seven distinct sets of OPV devices that were degraded under well-defined conditions in accordance with the ISOS-3 protocols. The degradation experiments lasted up to 1830 hours and involved more than 300 cells on more than 100 devices. The devices were analyzed and characterized at different points of their lifetimes by a large number of non-destructive and destructive techniques in order to identify specific degradation mechanisms responsible for the deterioration of the photovoltaic response. Work presented herein involves time-of-flight secondary ion mass spectrometry (TOF-SIMS) in order to study chemical degradation in-plane as well as in-depth in the organic solar cells. Various degradation mechanisms were investigated and correlated with cell performance. For example, photo-oxidation of the active material was quantitatively studied as a function of cell performance. The large variety of cell architectures used (some with and some without encapsulation) enabled valuable comparisons and important conclusions to be drawn on degradation behaviour. This comprehensive investigation of OPV stability has significantly advanced the understanding of degradation behaviour in OPV devices, which is an important step towards large scale application of organic solar cells. © 2012 the Owner Societies., This work has been supported by the Danish Strategic Research Council (2104-07-0022), EUDP (j.no. 64009-0050, 64009-0051) and the Danish National Research Foundation. Partial financial support was also received from the European Commission as part of the Framework 7 ICT 2009 collaborative project HIFLEX (grant no. 248678), partial financial support from the EUIndian framework of the ‘‘Largecells’’ project that received funding from the European Commission’s Seventh Framework Programme (FP7/2007–2013. grant no. 261936), partial financial support was also received from the European Commission as part of the Framework 7 ICT 2009 collaborative project ROTROT (grant no. 288565) and from PVERA-NET (project acronym POLYSTAR). are due to CONACYT (México) for the PhD scholarship awarded to G. T.-E; to the Spanish Ministry of Science and Innovation, MICINN-FEDER project ENE2008-04373; to the Consolider NANOSELECT project CSD2007-00041; to the Xarxa de Referència en Materials Avançats per a l’Energia, XaRMAE of the Catalonia Government (Spain). RR and HH are grateful for financial support from the Thuringian Ministry of Culture and the German Federal Ministry of Education and Research in the frameworks of FIPV II and PPP (contract number 13N9843), respectively. DMT acknowledges generous support from the Inger and Jens Bruun Foundation through The American-Scandinavian Foundation.

This work is part of the inter-laboratory collaboration to study the stability of seven distinct sets of state-of-the-art organic photovoltaic (OPV) devices prepared by leading research laboratories. All devices have been shipped to and degraded at RISO-DTU up to 1830 hours in accordance with established ISOS-3 protocols under defined illumination conditions. In this work, we apply the Incident Photon-to-Electron Conversion Efficiency (IPCE) and the in situ IPCE techniques to determine the relation between solar cell performance and solar cell stability. Different ageing conditions were considered: accelerated full sun simulation, low level indoor fluorescent lighting and dark storage. The devices were also monitored under conditions of ambient and inert (N 2) atmospheres, which allows for the identification of the solar cell materials more susceptible to degradation by ambient air (oxygen and moisture). The different OPVs configurations permitted the study of the intrinsic stability of the devices depending on: two different ITO-replacement alternatives, two different hole extraction layers (PEDOT:PSS and MoO 3), and two different P3HT-based polymers. The response of un-encapsulated devices to ambient atmosphere offered insight into the importance of moisture in solar cell performance. Our results demonstrate that the IPCE and the in situ IPCE techniques are valuable analytical methods to understand device degradation and solar cell lifetime. © 2012 the Owner Societies., This work has been supported by the Danish Strategic Research Council (2104-07-0022), EUDP (j.no. 64009-0050), and the Danish National Research Foundation. Partial financial support was also received from the European Commission as part of the Framework 7 ICT 2009 collaborative project HIFLEX (grant no. 248678), partial financial support from the EUIndian framework of the ‘‘Largecells’’ project that received funding from the European Commission’s Seventh Framework Programme (FP7/2007–2013. grant no. 261936), partial financial support was also received from the European Commission as part of the Framework 7 ICT 2009 collaborative project ROTROT (grant no. 288565) and from PVERA-NET (project acronym POLYSTAR). To CONACYT (México) for the Ph.D. scholarship awarded to G. T.-E, to the Spanish Ministry of Science and Innovation, MICINN-FEDER project ENE2008-04373, to the Consolider NANOSELECT project CSD2007-00041, to the Xarxa de Referència en Materials Avançats per a l’Energia, XaRMAE of the Catalonia Government (Spain). RR and HH are grateful for financial support from the Thuringian Ministry of Culture and the German Federal Ministry of Education and Research in the frameworks of FIPV II and PPP (contract number 13N9843), respectively. DMT acknowledges generous support from the Inger and Jens Bruun Foundation through The American–Scandinavian Foundation.

The investigation of degradation of seven distinct sets (with a number of individual cells of n ≥ 12) of state of the art organic photovoltaic devices prepared by leading research laboratories with a combination of imaging methods is reported. All devices have been shipped to and degraded at Risø DTU up to 1830 hours in accordance with established ISOS-3 protocols under defined illumination conditions. Imaging of device function at different stages of degradation was performed by laser-beam induced current (LBIC) scanning; luminescence imaging, specifically photoluminescence (PLI) and electroluminescence (ELI); as well as by lock-in thermography (LIT). Each of the imaging techniques exhibits its specific advantages with respect to sensing certain degradation features, which will be compared and discussed here in detail. As a consequence, a combination of several imaging techniques yields very conclusive information about the degradation processes controlling device function. The large variety of device architectures in turn enables valuable progress in the proper interpretation of imaging results - hence revealing the benefits of this large scale cooperation in making a step forward in the understanding of organic solar cell aging and its interpretation by state-of-the-art imaging methods. This journal is © 2012 The Royal Society of Chemistry., RR, MS, MB and HH are grateful for financial support from the Thuringian Ministry of Culture and the German Federal Ministry of Education and Research in the frameworks of FIPV II and PPP (contract number 13N9843), respectively. This work has been supported by the Danish Strategic Research Council (2104-07-0022), EUDP (j.no. 64009-0050) and the Danish National Research Foundation. Partial financial support was also received from the European Commission as part of the Framework 7 ICT 2009 collaborative project HIFLEX (grant no. 248678), partial financial support from the EUIndian framework of the ‘‘Largecells’’ project that received funding from the European Commission’s Seventh Framework Programme (FP7/2007–2013. grant no. 261936), partial financial support was also received from the European Commission as part of the Framework 7 ICT 2009 collaborative project ROTROT (grant no. 288565) and from PVERA-NET (project acronym POLYSTAR). To the Spanish Ministry of Science and Innovation, MICINN-FEDER project ENE2008-04373, to the Consolider NANOSELECT project CSD2007-00041, to the Xarxa de Refer encia en Materials Avanc¸ats per a l’Energia, XaRMAE of the Catalonia Government (Spain). To CONACYT (M exico) for the PhD scholarship awarded to GT-E. DMT acknowledges support from the Inger and Jens Bruun Foundation through The American–Scandinavian Foundation.

Seven distinct sets (n ≥ 12) of state of the art organic photovoltaic devices were prepared by leading research laboratories in a collaboration planned at the Third International Summit on Organic Photovoltaic Stability (ISOS-3). All devices were shipped to RISØ DTU and characterized simultaneously up to 1830 h in accordance with established ISOS-3 protocols under three distinct illumination conditions: accelerated full sun simulation; low level indoor fluorescent lighting; and dark storage with daily measurement under full sun simulation. Three nominally identical devices were used in each experiment both to provide an assessment of the homogeneity of the samples and to distribute samples for a variety of post soaking analytical measurements at six distinct laboratories enabling comparison at various stages in the degradation of the devices. Over 100 devices with more than 300 cells were used in the study. We present here design and fabrication details for the seven device sets, benefits and challenges associated with the unprecedented size of the collaboration, characterization protocols, and results both on individual device stability and uniformity of device sets, in the three illumination conditions. © 2012 The Royal Society of Chemistry., This work has been supported by the Danish Strategic Research Council (2104-07-0022), EUDP (j.no. 64009-0050) and the Danish National Research Foundation. Partial financial support was also received from the European Commission as part of the Framework 7 ICT 2009 collaborative project HIFLEX (grant no. 248678), partial financial support from the EUIndian framework of the ‘‘Largecells’’ project that received funding from the European Commission’s Seventh Framework Programme (FP7/2007–2013. grant no. 261936), partial financial support was also received from the European Commission as part of the Framework 7 ICT 2009 collaborative project ROTROT (grant no. 288565) and from PVERA-NET (project acronym POLYSTAR).

Photobleaching rates are investigated for thin films of poly(3-hexylthiophene) (P3HT) blends employing either an indene-C 60 bisadduct (ICBA) or [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) as the electron acceptor. Relative to the bisindene, PCBM significantly enhances resistance to photobleaching of the P3HT donor polymer. We tentatively attribute a decrease in the charge transfer rate as the mechanism responsible for the more rapid photobleaching in the sample containing the bisindene adduct. In order to elucidate the influence of the photobleaching rate on the initial performance of unencapsulated devices, we also monitored the time-dependent behavior for P3HT:fullerene inverted devices. Under conditions of constant illumination, we observe essentially identical behavior in device performance parameters regardless of the energy levels of the electron acceptor. We conclude that over the time frame measured for these devices, the primary degradation mechanism of the active layer is independent of the electron acceptor, despite the enhanced tolerance to photobleaching it may impart to the donor material.

The spectral characterization system presented in this work is one based on a monochromator and it is able to deliver an under — millimeter spot size. The system is fully controlled by computer, shows good repeatability and high accuracy in spectral characterization of photovoltaic devices by the determination of internal quantum efficiency over an extended wavelength range. Two solutions for extended range detectors are explored in this study: pyroelectric and sandwich detectors. Most of the results shown in this abstract were obtained using a pyroelectric detector. The full version of the paper will show a comparison between the two types of detectors. Scanning images (maps) of internal quantum efficiency (IQE) and of external quantum efficiency (QE) can be obtained with high spatial resolution both in AC and DC mode. I-V curves can be obtained in monochromatic or white light in the same location as the IQE curves without a supplemental repositioning. Because IQE curves and I-V curves are obtained in the same location and using the same optics, a full characterization of the photovoltaic device under test is possible in a single run.

19 páginas, 16 figuras, 16 tablas.-- El pdf del artículo es la versión pre-print.-- Trabajo presentado al "3rd International Summit on OPV Stability".-- et al., A large number of flexible polymer solar modules comprising 16 serially connected individual cells was prepared at the experimental workshop at Risø DTU. The photoactive layer was prepared from several varieties of P3HT (Merck, Plextronics, BASF and Risø DTU) and two varieties of ZnO (nanoparticulate, thin film) were employed as electron transport layers. The devices were all tested at Risø DTU and the functional devices were subjected to an inter-laboratory study involving the performance and the stability of modules over time in the dark, under light soaking and outdoor conditions. 24 laboratories from 10 countries and across four different continents were involved in the studies. The reported results allowed for analysis of the variability between different groups in performing lifetime studies as well as performing a comparison of different testing procedures. These studies constitute the first steps toward establishing standard procedures for an OPV lifetime characterization., This work was supported by: the Danish Strategic Research Council (DSF2104-07-0022), EUDP(j.nr.64009-0050), PV-ERA-NET (project acronym POLYSTAR),the Spanish Ministry of Science and Innovation, MICINN for the project ENE2008-04373 and CSIC for the PIE-200860I134. Financial support by the Austrian Research Promotion Agency (FFG), the Christian Doppler Research Association (CDG), the Austrian Federal Ministry of Economy, Family and Youth (BMWFJ) and the ISOVOLTAIC Gmb His gratefully acknowledged. Part of this work was supported by the PCCL(ProjectIV-1.02) with in the frame-work of the COMET-program of the Austrian Government. MH, TM, KL and MR would like to thank the Bundesministerium fuer Bildung und Forschung in the frame works of the InnoProfile project (03IP602), the OPEG project(13N9720) and the OPA project (13N9872). HH gratefully acknowledges funding with in the frame of BMBFOPV program. This work was partially supported by the King Abdullah University of Science and Technology and the Department of Energy, by KIST internal research fund under the Contract no. of 2E21831; by the European Commission as part of the Framework 7ICT2009 collaborative project HIFLEX(Grant Agreement no. 248678). RR, MS&HH acknowledge financial support from German Federal Ministry of Education and Research (BMBF)within‘‘Polymer Photovoltaics Processing’’(PPP) project (support code 13N9843).Part of this work was supported by the Victorian Organic Solar Cell Consortium.

Procedures for testing organic solar cell devices and modules with respect to stability and operational lifetime are described. The descriptions represent a consensus of the discussion and conclusions reached during the first 3 years of the international summit on OPV stability (ISOS). The procedures include directions for shelf life testing, outdoor testing, laboratory weathering testing and thermal cycling testing, as well as guidelines for reporting data. These procedures are not meant to be qualification tests, but rather generally agreed test conditions and practices to allow ready comparison between laboratories and to help improving the reliability of reported values. Failure mechanisms and detailed degradation mechanisms are not covered in this report. © 2011 Elsevier B.V. All rights reserved.

We provide the first NREL-certified efficiency measurement on an all-inorganic, solution-processed, nanocrystal solar cell. The 3% efficient device is composed of ZnO nanocrystals and 1.3 eV PbS quantum dots with gold as the top contact. This configuration yields a stable device, retaining 95% of the starting efficiency after a 1000-hour light soak in air without encapsulation.

The use of oxide materials as a hole transport layers (HTL) offers the opportunity to optimize hole collection in a bulk heterojunction organic photovoltaic (OPV) device. We discuss the use of NiO x deposited by three different methods, pulsed laser deposition, sputtering and a solution precursor as an alternative to the standard OPV HTL. We also examine the ability of the HTL to improve device performance in a bulk heterojunction device utilizing a donor that has a deeper highest occupied molecular orbital (HOMO) level‥

Organic photovoltaics (OPVs) are realizing power conversion efficiencies that are of interest for commercial production. Consequently, understanding device lifetime and mitigating degradation pathways have become vital to the success of a new industry. Historically, the active organic components are considered vulnerable to photo-oxidation and represent the primary degradation channel. We present several (shelf life and light soaking) studies pointing to the relative stability of the active layers and instabilities in commonly used electrode materials. We show that engineering of the metal electrode and hole/electron injection layer can lead to environmentally stable devices without encapsulation.

We report photovoltaic cells based on solution-processed blends using a novel anthradithiophene derivative as the donor and a fullerene derivative as the acceptor. Solvent vapor annealing of these blends leads to the formation of spherulites, which consist of a network of anthradithiophene crystallites dispersed in an amorphous matrix composed primarily of fullerene. We observe a direct correlation between coverage of a device with spherulites and its performance. Devices with 82% spherulite coverage reach a power conversion efficiency of 1%, which makes them one of the highest performing solution-processed small molecule photovoltaic cells to date.

We have utilized a commercially available metal–organic precursor to develop a new, low-temperature, solution-processed molybdenum oxide (MoOx) hole-collection layer (HCL) for organic photovoltaic (OPV) devices that is compatible with high-throughput roll-to-roll manufacturing. Thermogravimetric analysis indicates complete decomposition of the metal–organic precursor by 115 °C in air. Acetonitrile solutions spin-cast in a N2 atmosphere and annealed in air yield continuous thin films of MoOx. Ultraviolet, inverse, and X-ray photoemission spectroscopies confirm the formation of MoOx and, along with Kelvin probe measurements, provide detailed information about the energetics of the MoOx thin films. Incorporation of these films into conventional architecture bulk heterojunction OPV devices with poly(3-hexylthiophene) and [6,6]-phenyl-C61 butyric acid methyl ester afford comparable power conversion efficiencies to those obtained with the industry-standard material for hole injection and collection: poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The MoOx HCL devices exhibit slightly reduced open circuit voltages and short circuit current densities with respect to the PEDOT:PSS HCL devices, likely due in part to charge recombination at Mo5+ gap states in the MoOx HCL, and demonstrate enhanced fill factors due to reduced series resistance in the MoOx HCL.