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L’etonnement et la surprise sont des moteurs de reliaison psychique. Par la prime de plaisir que ces outils techniques suscitent, ils permettent de proposer une nouvelle narration de ce qui fait probleme. Ces concepts sont d’autant plus utiles qu’ils s’inscrivent dans le cadre de la puberte. Le psychotherapeute a avantage a conserver une grande capacite d’etonnement et de surprise au benefice de nouvelles possibilites de liaison psychique et a l’ecart du risque toujours present de l’effroi.

Kesterite Cu2ZnSn( S x Se 1 − x )4 is an attractive earth-abundant material for low-cost thin film photovoltaics with the capability to achieve power production in the terawatt range and therefore to supply a significant part of the global electricity needs. Despite its advantageous optical and electrical properties for photovoltaic applications, the large band tailing causes voltage losses that limit the efficiency of kesterite-based devices. Here we show that the band-tailing originates mainly from band-gap fluctuations attributable to chemical composition variations at nanoscale; while electrostatic fluctuations play a lesser role. Absorption measurement reveal that the Cu-Zn disorder, always present in kesterite Cu2ZnSn( S x Se 1 − x )4, is not the main source of the large band tailing. Instead defect clusters having a significant impact on the band-edge energies, e.g. [2 Cu Zn − + Sn Zn 2 + ], are proposed as the main origin for the kesterite band tail.

We have calculated the electrical conductivity of the solid oxide fuel cell (SOFC) cathode contact material La1–xSrxCoO3−δ at 900 K. Experimental trends in conductivity against x, and against δ for fixed x, are correctly reproduced for x ≲ 0.8. Furthermore, we have studied the chemistry of neutral and charged intrinsic and extrinsic defects (dopants) in La0.5Sr0.5CoO3 and have calculated the conductivity of the doped systems. In particular, we find that doping with Sm on the La site should enhance the conductivity, a prediction that is subsequently confirmed by electrical conductivity measurements.

The low photovoltaic efficiency of iron pyrite-based solar cells is often related to the presence of sulfur deficiencies. In this paper surfur-rich iron pyrite nanocrystals (FeS2 NCs) are synthesized by the hot injection method and deposited using layer by layer deposition. Optical absorption measurements show substantial sub-bandgap absorption, which is attributed to a sulfur-rich, thin surface layer. Microwave photoconductance measurements show very little signal of films with the original long ligands, while an approximately 100-fold higher signal is observed for films treated with FeCl2 and 1,2-ethanedithiol (EDT) solutions. In mesoporous hybrid systems of FeS2/SnO2 both sub-band-gap and above-band-gap photons lead to electron injection from FeS2 into the SnO2 conduction band. We explain these findings by proposing that pinning of the Fermi level by the surface layer leads to a downward band bending in the direction of the surface within the FeS2 NC. Hence, photoexcited electrons will first move towar...

In our recently published work, the positive effect of a Ge nanolayer introduced into the processing of Cu2ZnSnSe4 absorbers (CZTSe) was demonstrated. In this contribution, the complete optimizatio ...

Paracostibite (CoSbS) has recently been identified as a promising thermoelectric (TE) material, yet its full potential remains to be attained. We present herein an integrated method based on high throughput DFT computations validated with experiments that has allowed us to identify tellurium on antimony sites as a much more effective dopant than the formerly used nickel on cobalt sites. By carrying out a systematic adjustment optimization of the experimental parameters, we achieve a power factor as high as 2.7 mW m−1 K−2 at 543 K, which is maintained up to 730 K. This is, to the best of our knowledge, the largest value reported for polycrystalline metal sulfides.

Predicting a novel thermoelectric material requires the simultaneous optimization of several different factors. In this work we use two material design strategies to identify a new n-doped ternary sulfide thermoelectric using a high throughput framework. We have investigated a total of 234 ternary sulfides. Out of these, we identify five candidates that are thermodynamically stable and have bandstructures leading to favourable transport properties. We then predict the likelihood of n-doping, based on a high throughput defect analysis that characterizes the stability of the most favorable compensating intrinsic defects. This proved to be a crucial step which filters only one candidate without any stable electron killer defects. We also explore the possibility of improving the thermoelectric properties with thermal expansion, resulting in carrier pocket alignment. We demonstrate that in CoSbS several positive factors are simultaneously effective, i.e. good thermoelectric properties, correct bandgap, no intrinsic doping limit and an alignment of carrier pockets with volume increase.

In order to reduce the thermal conductivity of CoSbS, a newly developed thermoelectric semiconductor, we have aimed at intentionally induce atomic disorder in its structure. This endeavor was guided by Density Functional Theory(DFT) calculations which indicated that substituting sulfur with selenium might be easily achievable experimentally because of the low formation energy of this point defect. Thereby, CoSbS1−xSex compounds having 0 ≤ x ≤ 1 have been synthesized by solid state reaction. Besides the expected semiconducting paracostibite phase, we have observed the appearance of a semimetallic costibite phase, never reported experimentally before. This cross-fertilized theoretical and experimental approach allowed us to reduce by 50% the thermal conductivity of paracostibite and therefore reach a maximum zT of 0.62 at 730 K. This makes this entirely new CoSbS1−xSex alloy very attractive for further optimizations and potential usage in thermoelectric applications.

Accelerating the discovery of new materials is crucial for realizing the vision of need-driven materials development. In the present study we employ an integrated computational and experimental approach to search for new thermoelectric materials. High-throughput first principles calculations of thermoelectric transport coefficients are used to screen sulfide compounds conforming to the boundary conditions of abundant and innocuous components. A further computational screening step of substitutional defects is introduced, whereby SnS doped with monovalent cations is identified as having favorable transport properties. By silver doping of SnS under S-rich conditions an electric conductivity more than an order of magnitude higher than reported previously is realized. The obtained thermoelectric power-factor at room temperature is comparable to the state of the art for thermoelectric materials based on earth abundant, non-toxic elements. The high-throughput screening of extrinsic defects solves a long standing bottleneck in search of new thermoelectric materials. We show how the intrinsic carrier concentration in the low-temperature phase of SnSe is two orders of magnitude higher than in SnS. We furthermore find that the carrier concentration in SnSe can still be further optimized by silver doping.

Efficient copper zinc tin sulphide (Cu2ZnSnS4) thin film photovoltaic devices were fabricated with a new, fast, and simple preparation method using environmentally friendly solvents. Our process is based upon a versatile and instantaneous synthesis of a Cu–Zn–Sn–S colloid. Dispersing this colloid in a mixture of water (90%) and ethanol (10%), spraying it, and annealing sequentially the samples in two different gases allowed us to grow large grain, crystalline layers of promising photovoltaic quality. We measured cell efficiencies up to 5.0% under simulated AM1.5G (cell area 0.25 cm2). To the best of our knowledge, this is the highest reported efficiency reached with Cu2ZnSnS4 using a spray deposition technique with innocuous solvents.

Extremely thin absorber solar cells are built in which an Sb2S3 absorber coating is created by atomic layer deposition (ALD). The material is distributed homogeneously along the depth axis and is free of oxide. Under our conditions, an optimal thickness of 10 nm, Sb2S3, yields efficiencies of up to 2.6%.

In order to reduce the thermal conductivity of CoSbS, a newly developed thermoelectric semiconductor, we have aimed at intentionally induce atomic disorder in its structure. This endeavor was guided by Density Functional Theory(DFT) calculations which indicated that substituting sulfur with selenium might be easily achievable experimentally because of the low formation energy of this point defect. Thereby, CoSbS1−xSex compounds having 0 ≤ x ≤ 1 have been synthesized by solid state reaction. Besides the expected semiconducting paracostibite phase, we have observed the appearance of a semimetallic costibite phase, never reported experimentally before. This cross-fertilized theoretical and experimental approach allowed us to reduce by 50% the thermal conductivity of paracostibite and therefore reach a maximum zT of 0.62 at 730 K. This makes this entirely new CoSbS1−xSex alloy very attractive for further optimizations and potential usage in thermoelectric applications.

We track charge carriers dynamics from femtoseconds to nanoseconds in Cu 2 ZnSn(S/Se) 4 thin films by time resolved terahertz spectroscopy (TRTS) and time resolved micro wave conductivity measurements (TRMC). This includes trapping of photo carriers into band tail states followed by recombination with a time constant of 9.1 ns. The relatively long life time is likely caused by the localization into long living trap states rather than by a low concentration of recombination centers.

Photovoltaic thin film solar cells based on kesterite Cu2ZnSn(Sx,Se1–x)4 compounds (CZTSSe) have reached >12% sunlight-to-electricity conversion efficiency. This is still far from the >20% record devices known in Cu(In1–y,Gay)Se2 and CdTe parent technologies. A selection of >9% CZTSSe devices reported in the literature is examined to review the progress achieved over the past few years. These devices suffer from a low open-circuit voltage (Voc) never better than 60% of the Voc max, which is expected from the Shockley-Queisser radiative limit (S-Q limit). The possible role of anionic (S/Se) distribution and of cationic (Cu/Zn) disorder on the Voc deficit and on the ultimate photovoltaic performance of kesterite devices, are clarified here. While the S/Se anionic distribution is expected to be homogeneous for any ratio x, some grain-to-grain and other non-uniformity over larger area can be found, as quantified on our CZTSSe films. Nevertheless, these anionic distributions can be considered to have a negligible impact on the Voc deficit. On the Cu/Zn order side, even though significant bandgap changes (>10%) can be observed, a similar conclusion is brought from experimental devices and from calculations, still within the radiative S-Q limit. The implications and future ways for improvement are discussed.

Organic photovoltaic devices based on the donor:acceptor blend of poly[ N -9″-heptadecanyl-2,7-carbazole- alt -5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C 61 butyric acid methyl ester (PCBM) have received considerable attention in recent years due to their high power conversion efficiencies and the ability to achieve close to 100% internal quantum efficiency. However, the highest efficiencies were all attained using active layers of less than 100 nm, which is not ideal for either maximised potential performance or commercial viability. Furthermore, more recent reports have documented significant charge carrier trapping in these devices. In this paper two charge extraction techniques (photo-CELIV and time-of-flight) have been used to investigate the mobility and recombination behaviour in a series of PCDTBT:PCBM devices. The results not only confirm significant charge carrier trapping in this system, but also reveal close to Langevin-type bimolecular recombination. The Langevin recombination causes a short charge carrier lifetime that results in a short drift length. The combination of these two characteristics (trapping and fast bimolecular recombination) has a detrimental effect on the charge extraction efficiency when active layers greater than ∼100 nm are used. This accounts for the pronounced decrease in fill factor with increasing active layer thickness that is typically observed in PCDTBT:PCBM devices.

The silole-based non-Langevin conjugated polymer KP115 has been used to demonstrate that circuit resistance is a crucial parameter in time-of-flight measurements of organic photovoltaic cells, providing a resistance-dependent bimolecular recombination coefficient. The origin of this behaviour is the biphasic decay dynamics present in KP115:PCBM devices (observed using a novel time-dependent charge extraction technique), which time-of-flight cannot accurately characterise.

We have studied organic bulk heterojunction photovoltaic devices based on a bridged-bithiophene donor-acceptor type low-band gap polymer blended with PCBM and bis-PCBM. The impact of the molecular arrangement is discussed in terms of the correlation between the solar-cell performance and the degree of crystallization. Differential scanning calorimetry (DSC) and grazing-incidence X-ray diffraction (GIXRD) prove that films with bis-PCBM typically result in more amorphous blends than comparable films with PCBM. Electron tomography (ET) is used to visualize the three dimensional morphology of photoactive layers, confirming the presence of nanofibers, formed in different scales through the thickness in the blended films with mono and bis-fullerenes. (C) 2012 Elsevier B.V. All rights reserved

Here we report on organic photovoltaic's (OPV) suitable for low light applications. In this paper, we illustrate the impact of Rs and Rp for indoor and outdoor applications. In addition, we propose a simple physics approach to predict the behavior of organic solar cells under various illumination intensities through electrical modeling. The combination of simulation and modeling allows to define a set of design rules for OPVs under low light illumination. The performance of various organic solar cells under low light intensity is compared with our predictions and excellent correlation is found. OPV shows high performance under low light conditions.

Semitransparent inverted organic photodiodes are fabricated with a Baytron PH500 ethylene-glycol layer/silver grid as the top electrode. Reasonable performances are obtained under both rear- and front-side illumination and efficiencies up to 2% are achieved. Some light is shed on visual prospects through optical simulations for a semitransparent device of poly(3-hexylthiophene) (P3HT) and the C60 derivative 1-(3-methoxycarbonyl)propyl-1-phenyl[6,6]C71 (PC70BM) in the inverted structure. These calculations allow the maximum efficiency achievable to be predicted for semitransparent cells based on P3HT:PC70BM versus the transparency perception for a human eye. The simulations suggest that low-bandgap materials such as poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) have a better potential for semitransparent devices. In addition, the color range recognized by the human eye is predicted by the optical simulation for some semitransparent devices including different active layers.

Carbon bridged (C-PCPDTBT) and silicon-bridged (Si-PCPDTBT) dithiophene donor-acceptor copolymers belong to a promising class of low bandgap materials. Their higher field-effect mobility, as high as 10 -2 cm 2 V -1 s -1 in pristine films, and their more balanced charge transport in blends with fullerenes make silicon-bridged materials better candidates for use in photovoltaic devices. Striking morphological changes are observed in polymer:fullerene bulk heterojunctions upon the substitution of the bridging atom. XRD investigation indicates increased π-π stacking in Si-PCPDTBT compared to the carbon-bridged analogue. The fluorescence of this polymer and that of its counterpart C-PCPDTBT indicates that the higher photogeneration achieved in Si-PCPDTBT:fullerene films (with either [C60]PCBM or [C70]PCBM) can be correlated to the inactivation of a charge-transfer complex and to a favorable length of the donor-acceptor phase separation. TEM studies of Si-PCPDTBT:fullerene blended films suggest the formation of an interpenetrating network whose phase distribution is comparable to the one achieved in C-PCPDTBT-fullerene using 1,8-octanedithiol as an additive. In order to achieve a balanced hole and electron transport, Si-PCPDTBT requires a lower fullerene content (between 50 to 60 wt%) than C-PCPDTBT (more than 70 wt%). The Si-PCPDTBT:[C70]PCBM OBHJ solar cells deliver power conversion efficiencies of over 5%.

The spectroscopic response of a poly(3-hexylthiophene)/[6,6]-phenyl-C 61 -butyric acid methyl ester (P3HT/PCBM)-based bulk heterojunction solar cell is extended into the near infrared region (NIR) of the spectrum by adding the low bandgap polymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-ryclopenta[2,1-b;3,4-6]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] [PCPDTBT] to the blend. The dominant mechanism behind the enhanced photosensitivity ofthe ternary blend is found to be a two-step process: first, an ultrafast and efficient photoinduced charge transfer generates positive charges on P3HT and PCPDTBT and a negative charge on PCBM. In a second step, the positive charge on PCPDTBT is transferred to P3HT. Thus, P3HT serves two purposes. On the one hand it is involved in the generation of charge carriers by the photoinduced electron transfer to PCBM, and, on the other hand, it forms the charge transport matrix for the positive carriers transferred from PCPDTBT. Other mechanisms, such as energy transfer or photoinduced charge transfer directly between the two polymers, are found to be absent or negligible.

The characteristics of a power producing flexible wire based on organic photovoltaics (OPV) and the processes by which they are produced are described in this paper. A set of materials and coating formulations used on the electrode wires are very similar to those used in the development of two dimensional photovoltaic cells and modules. The active layer of the primary electrode wire comprises the bulk heterojunction-forming P3HT/PCBM (1:1 weight ratio) that has been extensively studied in planar cells. A second wire, which is wrapped around the coated, primary electrode wire, serves as the counter electrode. Ray tracing analysis indicates that light incident on the wires is focused by the cladding onto to the active layer, coated, primary electrode wire even when it is completely shadowed by the counter electrode. Furthermore, when the counter electrode is in a position that partially shadows the primary wire, a significant percentage of the light is reflected by the counter electrode onto the primary ele...

The realization of highly efficient organic solar cells requires the understanding of all optical losses in the solar cell. In this paper, we demonstrate the use of a nano-replicated moth eye anti-reflection coating which functions as an effective medium at the air-substrate interface. We show that the reflection losses of the substrate are compensated, yielding an increase of the peak EQE values by 3.5%. This improvement is valid for a wide range of incidence angles and preserves the insensitivity of organic solar cells against oblique incident light.

By annealing bulk-heterojunction solar cells made from blends of regioregular poly(3-hexylthiophene) (RR-PHT) and 1-(3-methoxycarbonylpropyl)-l-phenyl-[6,6] C 61 (PCBM) the quantum efficiency as well as charge carrier mobilities increases, while the bimolecular recombination coefficient decreases. We clarify the capacitance and conductivity properties of both annealed and non-annealed cells using the charge carrier extraction by linearly increasing voltage (CELIV) technique. We found that the capacitance in the annealed samples is a strong function of temperature, while the non-annealed samples show only the geometrical capacitance. The results can be explained by the demixing of the PCBM and RR-PHT and formation of high conductivity regions in the blend after the annealing process.

Kesterite semiconductors have been successfully employed in thin-film solar cells, with potential for high conversion efficiency solely from abundant materials. Although the best devices have come from mixed sulfo-selenide compounds, the underlying defect physics in this family has remained mysterious. The authors present a comprehensive study of electronic defects as a function of chalcogenide composition, providing a much needed, consistent view of shallow and deep levels in Cu${}_{2}$ZnSn(S,Se)${}_{4}$ and their consequences for device performance.

Intra grain charge carrier mobilities measured by time resolved terahertz spectroscopy TRTS in state of the art Cu2ZnSn S,Se 4 kesterite thin films are found to increase from 32 to 140 cm2V 1s 1 with increasing Se content. The mobilities are limited by carrier localization on the nanometer scale which takes place within the first 2 ps after carrier excitation. The localization strength obtained from the Drude Smith model is found to be independent of the excited photocarrier density. This is in accordance with bandgap fluctuations as cause of the localized transport. Charge carrier localization is a general issue in the probed kesterite thin films which were deposited by coevaporation, colloidal inks and sputtering followed by annealing with varying Se S contents and yield 4.9 to 10.0 efficiency in the completed device

The article traces the developments in the area of organic tandem solar cells. By piling several solar devices one over the other, a tandem cell is obtained. The light which is not absorbed in the lower cell can be absorbed in the upper cell. The thermalization losses are lowered due to the usage of materials having different bandgaps. By finding the appropriate dopants for both the p and the n region the efficiency of the stacked device can be boosted to 3.8%, which is 80% larger than that of a single device. It is postulated that efficiencies as high as 15% can be achieved.

As an answer to the increasing energy demand of mobile battery-powered electronic devices, we propose a new approach offering an autonomous power source. Comprising a thin film organic or hybrid solar cell connected to a Lithium-polymer (Li-polymer) battery, the so-called EURO-PSB device possesses attractive characteristics like low weight (

We report herein large area (>10 cm 2 ), interconnected organic solar cell modules both on glass substrates as well as on flexible ultra-high barrier foils, reaching 1.5% and 0.5% overall power conversion efficiency under AM1.5 conditions. Series connection is described, as these modules consist of up to three cells. Using our flexible barrier material, a shelf lifetime of polythiophene-based solar cells of 6000 h could be realized. Furthermore, we compare the photovoltaic performance of efficient conjugated polymer:fullerene solar cell modules with established technologies. Under typical indoor-office lighting, our modules are competitive with these systems.

Crystalline powders of the photovoltaic material candidate copper zinc tin sulfoselenide Cu2ZnSn(SxSe1–x)4 (CZTSSe) with x = S/(S + Se) from 0 to 1 were characterized by 119Sn solid state nuclear magnetic resonance (NMR) and by powder X-ray diffraction (PXRD). Two series of powders were characterized: one synthesized by a ceramic route and having cationic stoichiometry 2:1:1 and another one synthesized by a colloidal route, having a cationic Cu-poor Zn-rich composition and used as precursors for photovoltaic active films. The homogeneous anionic composition of the samples, which is a feature needed for the NMR analysis of the anionic distribution, has been proved by PXRD. The x values determined from the quantitative analysis of the 119Sn spectra are in very good agreement with those deduced by PXRD. In addition, the 119Sn spectra reveal, for the first time, the random distribution of the chalcogen atoms, which seems to be a general process. Finally, a qualitative, but thorough, analysis of the line width...

In order to comprehend the main limitations occurring in our 8.6% CZTSSe devices spray-coated from a water/ethanol ink, we have employed temperature dependent admittance spectroscopy and capacitance-voltage profiling. This technique has revealed a large density of charge carriers in the dark (1016–1017 cm−3) and two main defect levels: One fairly close to the middle of the band-gap, and another one much shallower (130 eV from the valence band maximum). A controlled tuning of the Sn content in the sprayed ink appears to offer an efficient leverage on the density of these defects: By adding only a few percent of Sn, the density of charge carriers in the dark can be reduced by more than one order of magnitude. This improvement of our process has led us to the fabrication of devices showing efficiencies close to 10% under AM1.5G.

Electronic and transport properties of Bi2S3 with various dopants are studied using density functional theory and experimental characterizations. First, principle calculations of thermoelectric properties are used to evaluate the thermoelectric potential of the orthorhombic Bi2S3 structure. The computational screening of extrinsic defects is used to select the most favorable n-type dopants. Among all the dopants considered, hafnium and chlorine are identified as prospective dopants, whereas, e.g., germanium is found to be unfavorable. This is confirmed by experiment. Seebeck coefficient (S) and electrical conductivity (σ) measurements are performed at room temperature on pellets obtained by spark plasma sintering. An increase of power factors (S2·σ) from around 50 up to 500 μW K−2 m−1 is observed for differently doped compounds. In several series of samples, we observed an optimum of power factor above 500 μW K−2 m−1 at room temperature for a chlorine equivalence of 0.25 mol. % BiCl3. The obtained results...

Tin(II)sulfide, SnS, is a commercially viable and environmentally friendly thermoelectric material. Recently it was shown how the carrier concentration and the thermoelectric power factor can be optimized by Ag-doping in a sulphur rich environment. Theoretical calculations lead to a fairly accurate estimation of the carrier concentration, whereas the potential of doping with Li(+) is strongly overestimated. Two principally ubiquitous effects that can result in decreasing the hole concentration, namely the formation of coupled defect complexes and oxidation of the dopant, are discussed as possible origins of this disagreement. It is shown that oxidation limits the chemical potential of Li beyond that already set by the formation of Li2S. This work serves as a comprehensive guide to achieve an efficient p-doped SnS thermoelectric material.

Charge carrier mobility (μ), recombination kinetics, and lifetime (τ) have been investigated with the photo-induced charge carrier extraction by linearly increasing voltage technique (photo-CELIV) in blends of poly[2-methoxy-5-(3,7-dimethyloctyloxy)-phenylene vinylene] (MDMO-PPV) and 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)-C61(PCBM). Different MDMO-PPV/PCBM ratios have been studied showing that increasing the PCBM content induces an increase of the photo-CELIV mobility up to two orders of magnitude. Simultaneously, the lifetime of the charge carriers decreases in such a way that the product μ × τ appears almost constant independently of the blend composition. Recombination kinetics close to the Langevin one is observed for all PCBM concentrations studied.

Results on photoresponsive organic field-effect transistors (photOFETs) based on conjugated polymer/fullerene solid-state mixtures as active semiconductor layer and poly-vinyl-alcohol (PVA) or divinyltetramethyldisiloxane-bis(benzocyclobutene) (BCB) as gate dielectrics are presented. With LiF/Al top source–drain contacts all devices show dominantly n-type transistor behaviour. Devices fabricated with PVA as gate insulator reveal gate voltage induced saturation upon illumination but low photostability. Contrary, devices fabricated with BCB as gate insulator show transistor amplification in a wide range of illumination intensities. The increase of the drain–source current by more than two orders of magnitudes upon illumination is explained by the generation of a large carrier concentration due to photoinduced charge transfer at the conjugated polymer/fullerene bulk heterojunction upon illumination (photodoping). After illumination, a change of the dark transfer characteristics with respect to the initial transfer characteristics was observed. The initial dark state is achieved either by applying a large negative gate bias or by annealing.

We report herein a shelf lifetime study of poly(2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene-vinylene) (MDMO-PPV) : 1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C61 (PCBM) solar cells encapsulated in a new flexible and transparent poly(ethylene naphthalate) (PEN)-based ultra-high barrier material entirely fabricated by plasma enhanced chemical vapor deposition (PECVD). We have found in this preliminary work that the encapsulation raises the shelf lifetime (50% of the initial efficiency) of 30 × 57 mm2 solar cells from a few hours into the range beyond 3000 h, or more than four months.

Hydrogenated nanocrystalline silicon (nc-Si:H) was deposited by plasma-enhanced chemical vapor deposition (PECVD) on transparent polymers in order to qualify these for possible use as electronic substrates. As a first step, plasma etch experiments in pure H 2 revealed small etch rates for these materials. Thin films of nc-Si:H were then deposited on samples placed on the grounded electrode of a Reinberg-type parallel plate RF (13.56 MHz) PBCVD reactor, at various substrate temperatures (25 °C < Ts ≤ 250 °C), using SiH4 diluted in H 2 as the feed-gas. Thermally induced failure of the nc-Si:H/polymer composite was avoided within a certain range of deposition conditions, permitting structural and electrical characterization of the deposits.

Conjugated polymers are widely used as electroactive materials because of their morphological changes induced by redox cycling. But this type of materials was recently shown to induce several other electromechanical actuations. While undoped conjugated polymer based diodes undergo common Maxwell stress and electro-thermal actuation under reverse and forward polarization, respectively, devices based on doped active material exhibit an unusual type of electromechanical strain. This strain, in between piezoelectricity and electrostriction, opens new routes for material investigation and potential applications in “smart” actuators.

Organic solar cells based on conjugated polymer:fullerene blends show nowadays efficiencies above 4%. After briefly presenting the science of bulk-heterojunction solar cells, we report herein a shelf lifetime study performed by encapsulating the cells in a flexible and transparent gas barrier material. This method allows lifetimes as reported for glass encapsulation. Moreover, we propose a new approach to pattern organic solar cells and design large-scale modules. This technique, based on selective Nd:yttrium aluminum garnet (YAG) laser etching, potentially enables low-cost, high-speed roll-to-roll operation.

Polyimide (PI) foils were coated with thin SiO x films for surface wettability improvement. The deposition was carried out in a microwave DECR (Distributed Electron Cyclotron Resonance) plasma reactor from a mixture of HMDSO/O 2 . During deposition, the PI substrate was located downstream, exposed to long-lived reactive precursors and to VUV radiation (position I) or located again downstream but shielded from VUV radiation (position II). Deposition time was varied in order to observe different stages of the film growth. The surfaces of the deposited films were investigated by means of contact angle, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) measurements. According to contact angle measurements, the coated PI surface became hydrophilic already at a thickness of about 2.8 nm and stayed nearly at the same level still for thicker coating. The plasma deposition of the ultra-thin SiO x layer increased significantly the polar component of the surface energy from 9 to 53 mJ . m - 2 and consequently enhanced the wettability of the material. The treated surfaces were only moderately affected after eight weeks storage time in air, indicating stable surface treatments. AFM images revealed that during deposition, the PI surface topography remains relatively smooth when coated in position I. However, for PI coated in position II, the surface roughness becomes more pronounced as thickness is increased. XPS analysis showed that VUV irradiation of the PI surface leads to the formation of a high proportion of polar species which enhance the wettability of the surface. Curve fitting of the Si2p peak showed that, as the film thickness increases, the deposited film becomes more oxidized.

Triggered by the outstanding worldwide growth of the photovoltaic market as well as by the need of alternative energy sources in future, organic solar cells are the object of vivid interest from both industrial and academic sides. Based on the semiconducting properties of organic conjugated macromolecules, these devices possess the potential to be processed by common printing techniques. Besides being easily upscalable on rigid as well as on flexible substrates, they open the route of roll-to-roll production of low cost renewable energy sources. Today, up to 5% power conversion efficiencies are reported in this kind of plastic solar cells.

Cu 2 ZnSn(S,Se) 4 thin film devices fabricated with a new, fast and environmental friendly preparation method are investigated by defect spectroscopy and transport measurements. Defect levels in sulfide-based as well as sulfur-selenide based kesterite devices are studied using admittance, temperature-dependent current-voltage analysis and photoluminescence. We find that the series resistance of the devices is activated with an energy of 80–100meV while the defect activation energies from admittance analysis shows activation energies of 200meV and 260meV for sulfur-based and Cu 2 ZnSn(S 0.6 Se 0.4 ) 4 devices, respectively. These admittance derived energies are consistent with the photoluminescence transition at a room temperature. The photoluminescence quenching activation energies of 130–140meV were determined for both devices and attributed to donor level of the quasi donor acceptor pair transition observed at low temperature.

Transparent inorganic oxide coatings on polymers are playing an increasingly important role in pharmaceutical, food, and beverage packaging, and more recently in encapsulation of organic, light-emitting display devices. Such coatings are being prepared by physical or by chemical vacuum-deposition methods. They possess barrier properties against permeation of gases or vapors when they are thicker than a certain critical thickness, dc; for d

International audience; Sb2S3 is widely considered to be an attractive photovoltaic material based on abundant, nontoxic elements. However, the maximum efficiency reported for solar cells based on this semiconductor does not exceed 6.5%. We have measured light intensity-dependent J-V curves, transient microwave photoconductivity, steady-state photocurrent grating, modulated photocurrent, and photoconductivity on Sb2S3-based samples. All techniques converge toward the same observation: the main recombination route controlling the density of charge carriers in the absorber is of an order greater than one and appears to stem from an exponentially decaying density of tail states within the conduction band of the material. This conclusion has direct and drastic implications for the performance of Sb2S3-based solar cells.

Incremental increase in dimethyl sulfoxide (or dimethyl formamide) in ortho-dichlorobenzene solution of poly [N -heptadecanyl-2,7-carbazole-alt-5,5- (4′, 7′ -di-2-thienyl- 2′, 1′, 3′ -benzothiadiazole)] (PCDTBT) gradually reduces the polymer-solvent interaction, the attraction forces between polymer chains become more dominant, and the polymer chains adopt a tight and contracted conformation with more interchain interactions, resulting in a progressive aggregation in both solutions and films. This was used to fine tune the morphology of PCDTBT/ PC71 BM based solar cells, leading to improved domain structure and hole mobility in the active layer, and significantly improved photovoltaic performance. The power conversion efficiency increased from 6.0% to 7.1% on devices with an active area of 1.0 cm2. © 2011 Crown.