Search

In the last few years, there has been an unprecedented progress in the increase of the power conversion efficiency of perovskite solar cells. Evidently, further advances in the efficiency of these devices will depend on the constraints imposed by the optical and electronic properties of their constituents. Quite apparently during the manufacturing process of a solar cell, there is an inevitable variation in the thicknesses of various functional layers, which affects the optoelectronic characteristics of the final sample. In this work, a possible strategy of the analysis of the solar cell performance is suggested, based on statistically averaging procedure of experimental data. We present a case study, in which the optoelectronic properties of the meso-structured perovskite solar cell (with a mesoporous TiO2 layer) are analyzed within the method providing a deeper understanding of the device operation. This method enables an assessment of the overall quality of the device, pointing pathways towards the maximum efficiency design of a perovskite solar cell by material properties tuning.

The unprecedented increase of photovoltaic perovskites performance metrics has been obscured by the puzzling phenomenology underlying the device's anomalous ionic/electronic landscape. Thus, the establishment of a reliable measurement protocol of efficiency measurements, unanimously adopted by the perovskite's community, is indeed necessary to ensure comparability of device performance between different research laboratories. Here, we report a control strategy of ionic-electronic cooperative relaxation phenomena, eliminating the “hysteria around hysteresis”. The procedure, based on mixed engineering strategies, solves the problem that arises from the difficulty of providing steady-state device operation conditions, capturing in turn the anomalous capacitive behavior. From the determination of an optimal scan rate for J–V modeling, we provide an experimental visualization of the interplay between perovskites' ionic and electronic responses. The results of this combined theoretical and experimental study identify key guidelines about assessment procedural of device performance that should be taken into account in future publications to further improve reproducibility in the research field.

Understanding defects is of paramount importance for the development of stable halide perovskite solar cells (PSCs). However, isolating their distinctive effects on device efficiency and stability is currently a challenge. We report that adding the organic molecule 3-phosphonopropionic acid (H3pp) to the halide perovskite results in unchanged overall optoelectronic performance while having a tremendous effect on device stability. We obtained PSCs with ∼21% efficiency that retain ∼100% of the initial efficiency after 1,000 h at the maximum power point under simulated AM1.5G illumination. The strong interaction between the perovskite and the H3pp molecule through two types of hydrogen bonds (HI and OH) leads to shallow point defect passivation that has a significant effect on device stability but not on the non-radiative recombination and device efficiency. We expect that our work will have important implications for the current understanding and advancement of operational PSCs.

Halide perovskite solar cells (PSCs) have already demonstrated power conversion efficiencies above 25%, which makes them one of the most attractive photovoltaic technologies. However, one of the main bottlenecks towards their commercialization is their long-term stability, which should exceed the 20-year mark. Additive engineering is an effective pathway for the enhancement of device lifetime. Additives applied as organic or inorganic compounds, improve crystal grain growth enhancing power conversion efficiency. The interaction of their functional groups with the halide perovskite (HP) absorber, as well as with the transport layers, results in defect passivation and ion immobilization improving device performance and stability. In this review, we briefly summarize the different types of additives recently applied in PSC to enhance not only efficiency but also long-term stability. We discuss the different mechanism behind additive engineering and the role of the functional groups of these additives for defect passivation. Special emphasis is given to their effect on the stability of PSCs under environmental conditions such as humidity, atmosphere, light irradiation (UV, visible) or heat, taking into account the recently reported ISOS protocols. We also discuss the relation between deep-defect passivation, non-radiative recombination and device efficiency, as well as the possible relation between shallow-defect passivation, ion immobilization and device operational stability. Finally, insights into the challenge and criteria for additive selection are provided for the further stability enhancement of PSCs.

We report a cooperative study conducted between different laboratories to investigate organic solar cell degradation with respect to P3HT material properties and different solar cell architectures. Various batches of P3HT were collected from different suppliers reflecting commercial availability as well as properties variability. Among the materials properties explicitly considered were the molar mass, dispersity, regio-regularity, impurities by trace metals and intrinsic doping evaluated from radical concentrations. Each of the participating laboratories contributing test devices applied their own layer stack, i.e. their own device architecture and layout. This variation was appreciated as another parameter for evaluation. Even though a large amount of devices failed due to extrinsic degradation effects, indeed, some materials properties were found to be more important than others for obtaining long lifetimes and high stability of P3HT-based polymer solar cells.

At the end of a rush lasting over half a century, in which CMOS technology has been experiencing a constant and breathtaking increase of device speed and density, Moore’s law is approaching the insurmountable barrier given by the ultimate atomic nature of matter. A major challenge for 21st century scientists is finding novel strategies, concepts and materials for replacing silicon-based CMOS semiconductor technologies and guaranteeing a continued and steady technological progress in next decades. Among the materials classes candidate to contribute to this momentous challenge, oxide films and heterostructures are a particularly appealing hunting ground. The vastity, intended in pure chemical terms, of this class of compounds, the complexity of their correlated behaviour, and the wealth of functional properties they display, has already made these systems the subject of choice, worldwide, of a strongly networked, dynamic and interdisciplinary research community. Oxide science and technology has been the target of a wide four-year project, named Towards Oxide-Based Electronics (TO-BE), that has been recently running in Europe and has involved as participants several hundred scientists from 29 EU countries. In this review and perspective paper, published as a final deliverable of the TO-BE Action, the opportunities of oxides as future electronic materials for Information and Communication Technologies ICT and Energy are discussed. The paper is organized as a set of contributions, all selected and ordered as individual building blocks of a wider general scheme. After a brief preface by the editors and an introductory contribution, two sections follow. The first is mainly devoted to providing a perspective on the latest theoretical and experimental methods that are employed to investigate oxides and to produce oxide-based films, heterostructures and devices. In the second, all contributions are dedicated to different specific fields of applications of oxide thin films and

Semiconductor oxides have been applied in photovoltaic technologies for many years. The remarkable versatility of their properties and the feasibility to be fabricated by simple, low-cost and easily scalable fabrication methods confers oxides a unique place in next generation photovoltaics (NGPVs). Their outstanding ability to preserve or improve device characteristics, even as a noncrystalline (amorphous) material, allows their application in flexible and semitransparent PVs devices and printed electronics. Basic (doped and undoped) semiconductor oxides have demonstrated to provide enhanced lifetime stability to state-of-the-art PVs such as Organic (OPV) and halide perovskite solar cells (PSCs), which is a significant step toward NGPVs industrialization and commercialization. But semiconductor oxides, in their more complex form, can also provide properties like magnetism, ferroelectricity, or pyroelectricity (among others), that collectively with the most classical materials, can deliver novel and innovative features. This chapter documents the most recent results observed when semiconductor oxides are applied in different NGPVs technologies. The chapter covers technologies like all-oxide solar cells where the oxide is not only part of the device but also acts as the main light harvesting material. The chapter also describes the application of oxides as part of OPV and PSCs where semiconductor oxides are mostly applied as barrier layers eliminating the use of expensive and unstable organic semiconductors, enhancing device lifetime.

We demonstrate for the first time, the real lifetime response of mixed halide perovskite solar cells (PSCs) for >1000 h under outdoor conditions and the exceptional photoresponse observed at low-light intensities attributed to the ionic-electronic nature of the material. The investigated devices were fabricated by utilizing mixed perovskites containing formamidinium (FA) and methylammonium (MA) cations, in a one step solution-process method through a solvent engineering approach. The devices’ architecture is FTO/TiO (blocking layer) TiO (mesoporous)/FAPbIMAPbBr/Spiro-OMeTAD/Au. Notably, low short circuit current (J) was observed at low light intensities (<50 W/m) together with high open circuit potential build-up, which resulted in high PCEs. This response is in agreement with a “double electronic-ionic transport” model of the halide perovskite where the ionic component dominates at low light intensities and the electronic component dictates at high light irradiances. Our results highlight the exceptional stability of mixed MA/FA mesoscopic PSCs when operated for >1000 h under real outdoor conditions and the strong ionic component observed at low light irradiation.

In this work, nanostructured thin films of ZnO were electrochemically grown on FTO substrates. The morphology was tuned by modifying the synthesis parameters. The synthesis was carried out by applying Zn(NO3)·6H2O as the sole component of the aqueous electrolyte, avoiding the use of capping agents. The composition and morphology of the prepared ZnO were characterized by energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM), respectively. The as-deposited films were applied as electrodes in dye sensitized solar cells (DSCs). The performance of the cells was investigated by J×V curves and IPCE (incident photon to charge carrier efficiency) measurements. The SEM analysis demonstrated a direct relationship between ZnO morphology and Zn precursor concentration. It has been shown that the lower the concentration is, the more porous the morphology is. Increasing the amount of dye adsorbed on the ZnO decreased the power conversion efficiency of the final DSCs. The best cell presented the following parameters: open circuit voltage VOC=0.59V, short circuit current JSC=7.64mA/cm2, fill factor FF=50.41%, and power conversion efficiency PCE=2.27%.

Accurate characterization and reporting of organic photovoltaic (OPV) device performance remains one of the important challenges in the field. The large spread among the efficiencies of devices with the same structure reported by different groups is significantly caused by different procedures and equipment used during testing. The presented article addresses this issue by offering a new method of device testing using >suitcase sample> approach combined with outdoor testing that limits the diversity of the equipment, and a strict measurement protocol. A round robin outdoor characterization of roll-to-roll coated OPV cells and modules conducted among 46 laboratories worldwide is presented, where the samples and the testing equipment were integrated in a compact suitcase that served both as a sample transportation tool and as a holder and test equipment during testing. In addition, an internet based coordination was used via plasticphotovoltaics.org that allowed fast and efficient communication among participants and provided a controlled reporting format for the results that eased the analysis of the data. The reported deviations among the laboratories were limited to 5% when compared to the Si reference device integrated in the suitcase and were up to 8% when calculated using the local irradiance data. Therefore, this method offers a fast, cheap and efficient tool for sample sharing and testing that allows conducting outdoor measurements of OPV devices in a reproducible manner.

Titania (TiO2) nanoparticles have been synthesized using organic precursor technique. The titania nanoparticles were characterized. The results indicated that the prepared titanium oxalate and citrate precursors were transformed to anatase TiO2 phase at temperature 400 °C for 2 h. Dye-sensitized solar cells were assembled using the prepared nanocrystalline TiO2 with large surface area. The specific surface area SBET was 80.9 and 78.6 m2/g using oxalic and citric acids, respectively. The power efficiency was 3.5 and 2.4%. A brief discussion on the possible reasons behind the low power conversion efficiency observed for these type of solar cells was reported.

In this work, a single-step synthesis route to prepare lauryl gallate capped TiO 2 nanoparticles has been established. Powder X-Ray diffraction analysis shows anatase as the predominant inorganic phase. UV-vis and FT-IR spectroscopy characterization denotes that lauryl gallate molecules are covalently linked to the particulate titania core through the enediolate group. The as prepared powder is easily dispersable in common organic solvents, such as tetrahydrofurane, methylethylketone and n-butanol, showing good stability under ambient atmosphere. This solution processable precursor facilitates thin film deposition on glass substrates. The capping gallate derivative also facilitates preparing translucent TiO 2-polystyrene composites. © 2012 Elsevier B.V.

A new encapsulation method for organic solar cells has been tested on flexible solar modules and cells embedded in polyurethane, sandwiched between a tempered glass plate and a polycarbonate plate. Panels, each containing 10 organic solar modules/cells, were fabricated and installed for outdoor exposure in eight different countries for 4½ months. In order to minimize potential deviations in procedures and equipment, one person was responsible for the fabrication, installation and initial and final IV-measurements of the panels using the same equipment for all measurements and calibrations. The encapsulated modules/cells showed significantly reduced degradation compared with previous studies, with final average efficiencies around 40% of the original after 4½ months outdoor exposure. Photodegradation was furthermore found not to be the primary source of degradation.

In this work, we study the effect of the transparent conducting oxide (TCO) and the polymer applied (MEH-PPV or P3HT) on the photovoltaic properties of TCO/TiO2/polymer/Ag bi-layer solar cells. The solar cells were analyzed under inert atmosphere conditions resembling an encapsulated or sealed device. We demonstrate that the substrate applied, ITO or FTO, modifies the crystalline structure of the TiO2: on an ITO substrate, TiO2 is present in its anatase phase, on an FTO, the rutile phase predominates. Devices fabricated on an FTO, where the rutile phase is present, show better stability under inert atmospheres than devices fabricated on an ITO, anatase phase. With respect to the polymer, devices based on MEH-PPV show higher Voc (as high as 1 V), while the application of P3HT results in lower Voc, but higher Jsc and longer device stability. These observations have been associated to (a), the crystalline structure of TiO2 and (b) to the form the polymer is bonded to the TiO2 surface. In-situ IPCE analyses of P3HT-based solar cells show a red shift on the peak corresponding to TiO2, which is not present on the MEH-PPV-based solar cells. The latter suggest that P3HT can be linked to the TiO2 though the S-end atom, which results in devices with lower Voc. All these observations are also valid for devices, where the bare TiO2 is replaced by an Nb–TiO2. The application of an Nb–TiO2 with rutile structure in these polymer/oxide solar cells is the reason for their higher stability under inert atmospheres. We conclude that the application of TiO2 in its rutile phase is beneficial for long-term stability devices. Moreover there is an interplay between low Voc and Jsc in devices applying P3HT, since power conversion efficiency can be partially canceled by their lower Voc in comparison with MEH-PPV. These findings are important for polymer/oxide solar cells, but also for organic solar cells, where a layer of semiconductor oxides are in direct contact with a polymer, like in an i

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.

Titanium dioxide based tubular nanocomposites containing long-chain amines were prepared by hydrothermal reaction of anatase with neutral surfactants, dodecylamine and octadecylamine, under strong alkaline conditions. Morphologically pure phases are obtained after reaction times of about 50 h at 130 °C. Dodecylamine derivates are structural and thermally more fragile than those with octadecylamine. Under more drastic reaction conditions, 72 h at 150 °C, amine is segregated leading to almost pure inorganic nanotubes or fibers for octadecyl and dodecyl derivatives respectively. The products characterized by electron microscopy, X-ray diffraction, FT-IR and elemental analysis are constituted by the hydrogen titanat H2Ti3O7. Diffuse reflectance spectra reveal the products present typical size-dependent optical properties. The photoluminescence spectra are qualitatively similar to that of anatase dominated by the presence of traps located in the band gap. The electrochemical lithium intercalation and lithium diffusion coefficients of the products were studied by intermittent galvanostatic method and galvanostatic pulse relaxation technique respectively. Products were tested in a lithium cell using the nanocomposites as the active material of the positive electrode. The hybrid dodecylamine derivative shows a first cycle irreversible capacity of 219 mAh/g, and a capacity of 113 mAh/g after the 7th cycle which results improved in comparison with those reported for H2Ti3O7 electrodes, thus pointing to a protective effect of the amine.

Hybrid Solar Cells (HSC) applying Nb-TiO2 in direct contact with a conducting organic polymer, MEH-PPV, show higher stability than the bare TiO2-based HSC when analyzed under inert atmosphere conditions. IPCE analyses revealed that inert atmospheres affect directly the semiconductor oxide in the first stages of the analyses but photovoltaic performance stabilizes after several hours. A 20 wt% Nb-doped TiO2 presented the highest stability and photovoltaic properties. The behavior has been attributed to the solubility limit of Nb within the TiO2 beyond 20 wt% doping level where the co-existence of NbO2 is observed. The HSCs were analyzed under controlled N2 atmosphere and 1000 W/m2 (AM 1.5) irradiation.

With the aim of improving the electrochemical properties of this candidate cathodic material for lithium ion batteries, a vanadium oxide (V2O5) and polypyrrole (Ppy) hybrid was prepared using pyridinesulfonic acid (PSA) as additive. The hybrid synthesis has been carried out in the literature by chemical polymerization of pyrrole in the host inorganic matrix, using the V2O5 dispersed in an acidic solution as an oxidizing agent. In this work the hybrid has been synthesised with PSA giving good results compared to other samples of the pristine V2O5 and to the Ppy/V2O5 hybrid without additive. An improvement of about 20% in the charge storage capacity has been achieved. The reasons for this improvement are discussed and analyzed using different experimental techniques. The hybrid material has the added advantage of an improved performance without the addition of any binder or conducting element as a cathode in a lithium ion battery.

Vanadium oxide (V2O5) is a candidate as cathodic material for lithium ion batteries. With the aim of improving the electrode performance, Polypyrrole (Ppy) has been proposed as binder and conducting element in the oxide structure. The hybrid synthesis has been carried out in the literature by chemical polymerization of Pyrrole in the host inorganic matrix, in some cases using the V2O5 dispersed in an acidic solution as an oxidizing agent. The hybrid material can be prepared using different acidic solutions that can influence the polymerization process affecting the electrochemical properties of the final hybrid material. The reasons and consequences for this influence are discussed and analyzed using different experimental techniques.

In order to prepare poly(N-vinyl carbazole) (PVK) and carbon nanotube (CNs) based composites, electrochemical polymerization of N-vinyl carbazole (NVK) was studied by cyclic voltammetry (CV) in LiClO4/acetonitrile solutions. Cyclic voltammograms recorded on a blank Pt electrode and those obtained when single or multi-walled carbon nanotubes (SWNTs or MWNTs) films were previously deposited onto the Pt electrode show a down-shift of the VK reduction peak potential in the latter case. The influence of monomer concentration and supporting electrolyte on the polymerization conditions and electrochemical properties of these composite materials were also investigated. Morphologic aspects as well as the photoluminescence properties of the PVK/CNs composite were also investigated. A covalent functionalization of carbon nanotubes with PVK is suggested on the basis of infrared (IR) spectroscopic studies. Using the PVK/CN composite as a positive electrode and an electrolytic solution containing LiPF6, a higher specific discharge capacity of the rechargeable lithium cells, 45 and 115 mA h g−1, are reported for PVK functionalized SWNTs and MWNTs, respectively.

Electrochemical polymerization of N-vinyl carbazole (VK) on carbon nanotube (CN) films was studied by cyclic voltammetry in LiClO4/acetonitrile solutions. Cyclic voltammograms recorded on a blank Pt electrode were compared with those obtained when single or multi-walled CN films were deposited on the Pt electrode; in the latter case, a down-shift of the VK reduction peak potential was observed. Functionalization of CNs with poly(N-vinyl carbazole) (PVK) was invoked by Raman scattering and UV–VIS–NIR spectroscopic studies. The influence of sweep rate on the electrochemical properties of the PVK/CN nanocomposite and the performance of supercapacitors constructed using PVK-functionalized single-walled carbon nanotube electrodes were also evaluated.

Hybrid organic–inorganic materials based on conjugated polymers constitute state-of-the-art compounds with recognized technological implications. In the area of energy conversion, production and storage devices, these materials have been applied as electrodes for batteries, supercapacitors, fuel cells or solar cells, among others. Their importance relies on the wide variety of organic and inorganic counterparts that these hybrids can be made of. The properties from each part can be tailored in order to contribute to a final desired characteristic or the combined properties from both. The unique combination of useful properties found in these materials include electronic conductivity (e− or h+), ionic transport, reversible electroactivity, electrooptical properties typical of semiconductors as well as electrochromic, pH- and composition-dependent properties, all of them to add to their polymeric nature. This is an excellent basis for the design of hybrid materials in which either of these properties or their combinations work to enhance or combine with those of a myriad inorganic phases with electronic, magnetic, photochemical, electrochemical, optical or catalytic properties. A large variety of functional hybrid materials can thus be designed and fabricated in which multifunctionality can be easily built to address specific technological needs. In this work we present our most recent results on new synthesis methodology developed for the chemical synthesis of the hybrid PAni/PMo12 and their application as electrochemical supercapacitors. We also report the synthesis of a new hybrid material of PEDOT/PMo12 synthesized for the first time by chemical methods and applied also in electrochemical supercapacitors. Initial results shows capacitance values as high as 168 F/g for the hybrid PAni/PMo12 and about 130 F/g for the hybrid PEDOT/PMo12.

We report the electrochemical deposition of nanostructured nickel-based solar absorber coatings on stainless steel AISI type 316L. A sol–gel silica-based antireflection coating, from TEOS, was also applied to the solar surface by the dip-coating method. We report our initial results and analyze the influence of the stainless steel substrate on the final total reflectance properties of the solar absorber. The relation between surface morphology, observed by SEM and AFM, the composition of the electrodeposited surfaces analyzed by X-ray powder diffraction and the study of different electrodeposition conditions and silica sol–gel coatings is described. The best solar absorptance and thermal emittance values obtained on stainless steel substrates were 0.91and 0.1, respectively.

Integration into a conducting polymer matrix to form a hybrid material is an effective way to harness the electrochemical activity of nanosized oxide clusters. By anchoring them into polyaniline, the reversible redox chemistry of the otherwise soluble polyoxometalate clusters can be combined with that of the conducting polymer and be put to work in energy storage applications. We present here preliminary results that show how the resulting hybrid polymer displays the combined activity of its organic and inorganic components to store and release charge in a solid state electrochemical capacitor device.

The application of a hybrid PAni-V2O5 cathode material in reversible lithium electrochemical cells is reported. We have studied the influence of synthesis conditions and subsequent treatments of the hybrid under oxygen in order to optimize its performance as a lithium-insertion cathode. The temperature and length of this treatment is a key parameter in determining the final specific charge of the cathode. The optimal material yielded a specific charge as high as 302 Ahkg-1 measured at low discharge rate (C/48) corresponding to the insertion of 2.72 lithium ions per formula unit (C6H4N)0.6V2O5-0.3H 2O). Higher scan rates of C/12 lead to specific capacities of 200 Ahkg-1. The thermal and electrochemical stability of the hybrid, especially in relation to the decomposition of the organic polymer and their effect on battery performance and cyclability are also discussed.

The synthesis, and spectroscopic and structural characterization of a series of hybrid PAni/V2O5 materials are reported. We have performed a systematic study of the synthesis of the hybrids by direct in situ reaction of aniline with V2O5 hydrogels and have determined key parameters for the reproducibility of the materials obtained. We have established the existence of two phases in the PAni/V2O5 system corresponding to the intercalation of one and two monolayers of PAni into V2O5. The characterization of these materials includes FTIR spectroscopy, X-ray diffraction, Thermogravimetric analyses, and resistivity measurements

The oxidative polymerization of aniline or pyrrole by phosphomolybdic acid (H3PMo12O40) is described. These reactions take place in the absence of other anions and result in the incorporation of the photoactive and electroactive PMo12O403− anion into the lattice of the polymer. The resulting hybrid materials present the good conductivity and polymeric nature of the matrix plus the added electroactivity of the inorganic cluster, which is anchored in the polymer and not exchanged upon reduction. The hybrids can work as electrodes harnessing the electrochemical properties of the polyoxometalic clusters

We have synthesized mixed-valence derivatives of the layered oxide HLa Nb2O7, structurally related to perovskite, by chemical reduction, either at room temperature or at 650°C. The thermal behavior of this compound, its structure and change in transport properties upon high temperature doping are discussed. High temperature reduction turns the white insulating precursor into a mixed-valence blue bronze with a layered structure and semiconducting-like properties.