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[Hybrid halide perovskite solar cells generally show differences in the power output depending on the voltage sweep direction, an undesired phenomenon termed hysteresis. Although the causes of this behavior have not yet been univocally determined, commonly, hysteresis heavily affects solar cells based on flat TiO2 as electron extracting layer. Herein, it is shown how perovskite material quality has a preeminent impact on hysteresis, and how combined deposition and post-deposition engineered manufacturing could lead to highly efficient and hysteresis-less solar cells, notwithstanding a planar TiO2-based layout. This methodology relies on solvent engineering during the casting process, leading to an ultra-flat, uniform, and thick film ensuring an optimal interface connection with the charge-extracting layer combined with post-deposition thermal and vacuum treatments, which merge the crystalline domains and cure the defects at the grain boundaries. This method allows obtaining perovskite active layer with superior optical properties, explaining the ideal device behavior and performances, therefore, a simple optimization of perovskite processing conditions can efficiently stem hysteresis targeting different device layouts. Power conversion efficiency of 15.4% and reduced hysteresis are achieved. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA., Weinheim.]

Hybrid perovskites are among the most promising materials for optoelectronic applications. Their 2D crystalline form is even more interesting since the alternating inorganic and organic layers naturally forge a multiple quantum-well structure, leading to the formation of stable excitonic resonances. Nevertheless, a controlled modulation of the quantum well width, which is defined by the number of inorganic layers (n) between two organic ones, is not trivial and represents the main synthetic challenge in the field. Here, a conceptually innovative approach to easily tune n in lead iodide perovskite single-crystalline flakes is presented. The judicious use of potassium iodide is found to modulate the supersaturation levels of the precursors solution without being part of the final products. This allows to obtain a fine tuning of the n value. The excellent optical quality of the as synthesized flakes guarantees an in-depth analysis by Fourier-space microscopy, revealing that the excitons orientation can be manipulated by modifying the number of inorganic layers. Excitonic out-of-plane component, indeed, is enhanced when "n" is increased. The combined advances in the synthesis and optical characterization fill in the picture of the exciton behavior in low-dimensional perovskite, paving the way to the design of materials with improved optoelectronic characteristics.

Nowadays it is well-accepted to attribute bulk-like optical absorption properties to colloidal PbS quantum dots (QDs) at wavelengths above 400 nm. This assumption permits to describe PbS QD light absorption by using bulk optical constants and to determine QD concentration in colloidal solutions from simple spectrophotometric measurements. Here we demonstrate that PbS QDs experience the quantum confinement regime across the entire near UV-vis-NIR spectral range, therefore also between 350 and 400 nm already proposed to be sufficiently far above the band gap to suppress quantum confinement. This effect is particularly relevant for small PbS QDs (with diameter of ≤4 nm) leading to absorption coefficients that largely differ from bulk values (up to ∼40% less). As a result of the broadband quantum confinement and of the high surface-to-volume ratio peculiar of nanocrystals, suitable surface chemical modification of PbS QDs is exploited to achieve a marked, size-dependent enhancement of the absorption coefficients compared to bulk values (up to ∼250%). We provide empirical relations to determine the absorption coefficients at 400 nm of as-synthesized and ligand-exchanged PbS QDs, accounting for the broadband quantum confinement and suggesting a heuristic approach to qualitatively predict the ligand effects on the optical absorption properties of PbS QDs. Our findings go beyond formalisms derived from Maxwell Garnett effective medium theory to describe QD optical properties and permit to spectrophotometrically calculate the concentration of PbS QD solutions avoiding underestimation due to deviations from the bulk. In perspective, we envisage the use of extended π-conjugated ligands bearing electronically active substituents to enhance light-harvesting in QD solids and suggest the inadequacy of the representation of ligands at the QD surface as mere electric dipoles.

We present a large area trifunctional glass prototype combining a photo-electrochromic (PEC) device and an organic light-emitting diode (OLED), interfaced through a properly designed electronic control system. A 12×17 cm2 PEC glass-on-glass module was realized, containing four dyesensitized solar cells (DSSCs) and a central electrochromic (EC) section deposited on the same glass panel. All PEC layers are screen-printed, including the mesoporous electrochromic layer, obtained from a custommade tungsten paste. DSSCs show an efficiency of 2.4%, while the coloration efficiency of the EC section reaches a value of 40 cm2C−1 at 700 nm. A 10×8 cm2 transparent white OLED was also realized, designed and tailored in order to unbalance the emission of light, i.e. maximizing the bottom emission. The efficiency of large area OLED section reaches 8 cd A-1 in the operative conditions and without light outcoupling enhancement systems. The OLED device is clamped on the back of the PEC module and all sections are electrically connected to an external electronic control system. The energy collected by the DSSCs is stored in supercapacitors and used when requested, either applied to the EC section to produce a light shading effect in the daytime, or to the OLED for illumination at night.

Herein, we present, for the first time, the features of a full solid-state electrochromic (EC) device fabricated on a single substrate, made of glass as well as flexible plastic, adopting a low-cost, eco-friendly, and facile fabrication process. By combining a solution processing of Nafion electrolyte film and RF sputtering deposition at room temperature (RT) on Nafion, we obtained monolithic systems with a simplified architecture (substrate/ITO/WO3/Nafion/ITO) in which a suitable Nafion film (8 µm thick) tightly shares its interfaces with the WO3 layer and the highly transparent and conductive RF-sputtered ITO film. Compared to conventional sandwich-type EC devices using semi-solid or liquid electrolytes, the resulting devices exhibited a strong enhancement in terms of interface properties, robustness, cyclic stability, and long-term durability (at least 1000 chronoamperometric cycles). Moreover, electro-optical characterizations highlighted high transmittance modulation (49% at 650 nm), astonishing results in terms of coloration efficiency (139 cm2/C), and low energy absorption (80 mW s/cm2).

Herein, an insulating biopolymer is exploited to guide the controlled formation of micro/nano-structure and physical confinement of alpha-delta mixed phase crystalline grains of formamidinium lead iodide (FAPbI(3)) perovskite, functioning as charge carrier concentrators and ensuring improved radiative recombination and photoluminescence quantum yield (PLQY). This composite material is used to build highly efficient near-infrared (NIR) FAPbI(3) Perovskite light-emitting diodes (PeLEDs) that exhibit a high radiance of 206.7 W/sr*m(2), among the highest reported for NIR-PeLEDs, obtained at a very high current density of 1000 mA/cm(2), while importantly avoiding the efficiency roll-off effect. In depth photophysical characterization allows to identify the possible role of the biopolymer in i) enhancing the radiative recombination coefficient, improving light extraction by reducing the refractive index, or ii) enhancing the effective optical absorption because of dielectric scattering at the polymer-perovskite interfaces. Our study reveals how the use of insulating matrixes for the growth of perovskites represents a step towards high power applications of PeLEDs. Funding Agencies|Regione Puglia through Samset2018 [r_puglia/A00_137/PROT/17/07/2017/001578]; MIUR (Italian Ministry of University and Research) through PRIN PERovskite-based Solar cells: towards high Efficiency and lOng-term stability (PERSEO) [20155LECAJ]; Fondazione di Sardegna - Convenzione triennale tra la Fondazione di Sardegna e gli Atenei Sardi Regione Sardegna [L.R. 7/2007, F72F16003040002]; SIR project "Two-Dimensional Colloidal Metal Dichalcogenides based Energy-Conversion Photovoltaics" (2D ECO), Bando SIR (Scientific Independence of young Researchers) 2014 MIUR Decreto Direttoriale 23 gennaio 2014 [197, RBSI14FYVD, CUP: B82I15000950008]; Regione Puglia; ARTI [LSBC6N4, GOWMB21]; China Scholarship Council

Here we investigate charge carrier generation and extraction processes in hybrid polymer/nanocrystal solar cells by means of time-resolved optical and photoelectrical techniques. We addressed the role of both poly(3-hexylthiophene) and colloidal arenethiolate-capped PbS quantum dots, which constitute the hybrid composite nanomaterial, in the photoinduced processes most relevant to device operation by changing the compositional ratio and applying chemical and thermal postdeposition treatments. The carrier generation processes were found to be wavelength-dependent: excitons generated in the polymer domains led to long-lived weakly bound charge pairs upon electron transfer to PbS nanocrystals; whereas charge carrier generation in the nanocrystal domains is highly efficient, although effective separation required the application of external electric field. Overall, charge carrier generation was found efficient and almost independent of the strength of applied electric field; therefore, competition between separation of electron–hole pairs into free carriers and geminate recombination is the major factor limiting the fill factor of nanocomposite-based solar cells. Device efficiency improvements thus require faster interfacial charge transfer processes, which are deeply related to the refinement of nanocrystal surface chemistry.

Transparent conducting oxides (TCOs) are emerging as possible alternative constituent materials to replace noble metals such as silver and gold for low-loss plasmonic applications in the near-infrared (NIR) and mid-infrared (MIR) regimes. In particular, TCO-based nanostructures are extensively investigated for biospectroscopy exploiting their surface-enhanced infrared absorption (SEIRA). The latter enhances the absorption from vibrational and rotational modes of nearby biomolecules, making TCO nanostructures a promising candidate for IR sensing applications. Nevertheless, in order to produce inexpensive devices for lab-on-a-chip diagnostics, it would be favorable to achieve surface-enhanced infrared absorption with very simple microstructures not requiring nanosize control. In this work, we attempt to demonstrate a SEIRA effect with the least challenging fabrication, ?m-scale instead of nm-scale, by tailoring both device design and charge density of the indium tin oxide (ITO) film. We show that microperiodic hole arrays in a ITO film are able to produce SEIRA via grating coupling. Such a study opens the way for innovative and disrupting biosensing devices. © 2018 American Chemical Society.

The integration of energy-saving electrochromic systems with novel functions and features in a single smart multifunctional device promises to achieve remarkable technological advancements for a wide range of consumer products showing more versatility, responsivity to different external inputs, and ability to operate in interactive modes. Here, we report a novel architecture in which a solid-state electrochromic cell and a solid-state organic light emitting diode are fully integrated in a single, highly transparent, solid-state electrochromic OLED device. This multifunctional device is capable of tuning its optical properties such as transmittance (chromic transition) and of producing light by electroluminescence, simultaneously or independently. The rational design of the solid-state electrochromic cell and the highly transparent OLED enables the construction of the integrated device in a monolithic unit. In such a structure the photonic architecture of the OLED device not only guarantees high transmittance, but, operating synergically with the electrochromic component, it outperforms the optical properties and electrochromic responses by the interference phenomenon, achieveing an optical contrast of 57% (ΔTbleaching/colouring @ 650 nm), and a coloration efficiency of 169 cm2 C−1, with very low energy consumption (80 mW cm−2). The OLED component exhibits luminance above the minimum values required for display and lighting applications, which are 300 cd m−2 and above 800 cd m−2, respectively. This result represents a further step towards the development of next-generation multifunctional EC devices such as full solid-state photoelectrochromic devices, and, importantly, this can open the way for new electrochromic “smart” window systems such as retail display windows or display EC glasses for augmented reality.

We exploit TiO2 surface functionalization as a tool to induce the crystallization process of CH3NH3PbI3−xClx perovskite thin films resulting in a reduction of the degree of orientation of the (110) crystallographic planes. Notably, the variation of the film crystalline orientational order does not affect the photovoltaic performances of the perovskite-based devices, whose efficiency remains mostly unchanged. Our findings suggest that other factors are more significant in determining the device efficiency, such as the non-homogenous coverage of the TiO2 surface causing charge recombination at the organic/TiO2 interface, defect distribution on the perovskite bulk and at the interfaces, and transport in the organic or TiO2 layer. This observation represents a step towards the comprehension of the perovskite film peculiarities influencing the photovoltaic efficiency for high performance devices.

Photovoltachromic devices combine photovoltaic and electrochromic behaviours to enable adjustable transparency glazing, where the photovoltaic component supplies the power to drive the coloration. Such stand-alone, self-powered devices are of commercial interest for integration into windows and surfaces of buildings and vehicles. Here, we report for the first time a perovskite-based photovoltachromic device with self-adaptive transparency. This multifunctional device is capable of producing electrical power by solar energy conversion as well as undergoing a chromic transition from neutral-color semi-transparent to dark blue-tinted when irradiated with solar light, without any additional external bias. The combination of semi-transparent perovskite photovoltaic and solid-state electrochromic cells enables fully solid-state photovoltachromic devices with 26% (or 16%) average visible transmittance and 3.7% (or 5.5%) maximum light power conversion efficiency. Upon activating the self-tinting, the average visible transmittance drops to 8.4% (or 5.5%). These results represent a significant step towards the commercialization of photovoltachromic building envelopes.

Due to their extraordinary quality factor and extreme sensitivity to surface perturbations, Bloch surface waves (BSW) have been widely investigated for sensing applications so far. Over the last few years, on-chip control of optical signals through BSW has experienced a rapidly-expanding interest in the scientific community, attesting to BSW's position at the forefront towards on-chip optical operations. The backbone of on-chip optical devices requires the choice of integrated optical sources with peculiar optic/optoelectronic properties, the efficient in-plane propagation of the optical signal and the possibility to dynamic manipulate the signal through optical or electrical driving. In this paper, we discuss our approach in addressing these requirements. Regarding the optical source integration, we demonstrate the possibility to couple the MoS2 mono- and bi-layers emission-when integrated on top of a 1D photonic crystal-to a BSW. Afterward, we review our results on BSW-based polariton systems (BSWP). We show that the BSWPs combine long-range propagation with energy tuning of their dispersion through polariton-polariton interactions, paving the way for logic operations.

The strong coupling of an excitonic transition with an electromagnetic mode results in composite quasi-particles called exciton polaritons, which have been shown to combine the best properties of their individual components in semiconductor microcavities. However, the physics and applications of polariton flows in organic materials and at room temperature are still unexplored because of the poor photon confinement in such structures. Here, we demonstrate that polaritons formed by the hybridization of organic excitons with a Bloch surface wave are able to propagate for hundreds of microns showing remarkable third-order nonlinear interactions upon high injection density. These findings pave the way for the study of organic nonlinear light–matter fluxes and for a technologically promising route of the realization of dissipation-less on-chip polariton devices operating at room temperature. The propagation and energy renormalization of exciton-polaritons, hybrid states of exciton and photon, can be controlled in an organic semiconductor at room temperature. Giovanni Lerario of CNR NANOTEC in Italy and co-workers fabricated a distributed feedback reflector from alternating layers of titanium dioxide and silicon dioxide on a glass substrate and coated it with a 35 nm thick layer of a perylene derivative. This cavity structure supports a novel type of polariton called Bloch surface wave polariton (BSWP), which propagates for more than 100 mm with a group velocity as high as of 150 mm ps-1. The resonance wavelength of the polariton is blue-shifted with increasing pump power into the distributed feedback reflector, indicating that the energy of the BSWP can be tuned. The results give hope for realizing on-chip polariton devices working at room temperature.

Due to a still limited understanding of the reasons making 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) the state-of-the-art hole-transporting material (HTM) for emerging photovoltaic applications, the molecular tailoring of organic components for perovskite solar cells (PSCs) lacks in solid design criteria. Charge delocalization in radical cationic states can undoubtedly be considered as one of the essential prerequisites for an HTM, but this aspect has been investigated to a relatively minor extent. In marked contrast with the 3-D structure of Spiro-OMeTAD, truxene-based HTMs Trux1 and Trux2 have been employed for the first time in PSCs fabricated with a direct (n-i-p) or inverted (p-i-n) architecture, exhibiting a peculiar behavior with respect to the referential HTM. Notwithstanding the efficient hole extraction from the perovskite layer exhibited by Trux1 and Trux2 in direct configuration devices, their photovoltaic performances were detrimentally affected by their poor hole transport. Conversely, an outstanding improvement of the photovoltaic performances in dopant-free inverted configuration devices compared to Spiro-OMeTAD was recorded, ascribable to the use of thinner HTM layers. The rationalization of the photovoltaic performances exhibited by different configuration devices discussed in this paper can provide new and unexpected prospects for engineering the interface between the active layer of perovskite-based solar cells and the hole transporters.

The development of alternative deposition techniques of conjugated polymeric compounds is an important step towards the fabrication of low cost multi-layered organic light emitting diodes suitable for display or lighting applications. In this work we show a white light -emitting polymeric hetero-structured diode consisting of three-stacked blue, red and green light emitting polymers. In order to circumvent the issue of selecting orthogonal solvents in solution -deposition approaches, we combine spin-coating with the Matrix Assisted Pulsed Laser Evaporation technique, resulting in the realization of a polymeric multilayered stack. By controlling the carriers and the energy transfer across the three light emitting layers interfaces, as well as the interplay between the deposition parameters, a pure white colour emission with Commission Internationale de l'Éclairage coordinates (X=0.327, Y=0.374) and a Color Rendering Index of 70 have been achieved. Our study represents the first proof of a light emitting diode made by multilayer polymeric thin films emitting white light.

Three different families of chemically engineered rod-shaped CdSe/CdS colloidal nanocrystals have been embedded into a poly(methyl methacrylate) matrix to realize a set of color-tunable photoluminescent filters for RGB light emitting devices, which demonstrate excellent optical transparency (in the range of wavelengths not corresponding to nanocrystal absorption), efficient photoluminescence and good thermal- and photo-stability. Accurate morphological and optical characterization of nanocomposite foils is provided as a function of nanorod size and content, and their color conversion properties are investigated in combination with a blue-emitting LED source. This approach combines the tunable optical features of inorganic quantum-confined light emitters with the facile processability of the polymeric host and offers a highly versatile design tool, which can be exploited in a wide spectrum of lighting and photonic devices. The preparation procedure reported here is even compatible with the implementation of an engineered array of microlens on the front-end surface of the nanocomposite foil and thus makes possible a tailored control of the color-converted photometric pattern.

In this work, we investigate the optical and structural properties of the well-known triplet emitter bis(4',6'-difluorophenylpyridinato)-iridium(III) picolinate (FIrpic), showing that its ability to pack in two different ordered crystal structures promotes attractive photophysical properties that are useful for solid-state lighting applications. This approach allows the detrimental effects of the nonradiative pathways on the luminescence performance in highly concentrated organic active materials to be weakened. The remarkable electro-optical behavior of sky-blue phosphorescent organic light-emitting diodes incorporating crystal domains of FIrpic, dispersed into an appropriate matrix as an active layer, has also been reported as well as the X-ray diffraction, nuclear magnetic resonance, electro-ionization mass spectrometry, and scanning electron microscopy analyses of the crystalline samples. We consider this result as a crucial starting point for further research aimed at the use of a crystal triplet emitter in optoelectronic devices to overcome the long-standing issue of luminescence self-quenching.

We present a novel, facile, and cost-effective method to prepare highly transparent mesoporous films made by anatase TiO2 nanorods that have been synthesized by a single-step solvothermal process. Such nanorods have been conveniently used as prepared-without completely removing the residual organics-to obtain suitable screen-printable paste by means of the use of proper polymeric binders. This method has been successfully implemented to fabricate highly efficient nanorod-based photoelectrodes for dye-sensitized solar cells. They showed an increment of the overall quantum conversion efficiency comprised between 34% and 58% with respect to cells based oil commercial P25 titanium dioxide nanoparticles. In particular, a maximum photocurrent density and solar conversion efficiency of 16.9 mA/cm(2) and 7.9% have been obtained, respectively.

Thermal evaporation of green-light emitting perovskite (MaPbBr3) films is reported. Morphological studies show that a soft thermal treatment is needed to induce an outstanding crystal growth and film organization. Hetero-structured light-emitting diodes, embedding as-deposited and annealed MAPbBr3 films as active layers, are fabricated and their performances are compared, highlighting that the perovskite evolution is strongly dependent on the growing substrate, too.

Bottom-contact n-channel OFETs basedon spin-coated films of N,N'-1H,1H-perfluorobutyl dicyanoperylenediimide (PDI-FCN(2)) exhibit a saturation-regime mobility of 0.15 cm(2) V(-1) s(-1) in vacuum and good air stability. These performances are attributed to the high crystallinity and to the edge-on orientation promoted by the thermal treatment, as showed by confocal laser microscopy.

We have developed a totally dry technique for the deposition of colloidal semiconductor nanocrystals on organic substrates. This approach is fully compatible with current organic LED technology. It appears that the slow evaporation of drop-cast QD films is critical for the success of the transfer process. This novel approach has been utilized to fabricate a hybrid organic–inorganic red LED

none 11 no Highly soluble air-stable conjugated decamers and polymers (compounds 1−6) with alternating “sulfur-overrich” bis(3,4′-S-alkyl)-2,2′-bithiophenes as the donor units and 2,1,3- benzothiadiazoles as the acceptor units were designed and expediently synthesized with the aid of microwave and ultrasound enabling technologies. Solid-state cyclovoltammetry showed that 1−6 had oxidation and reduction potentials in the range 0.6−0.9 V and −1/−1.2 V (vs SCE), respectively, with energy gaps below 2 eV. The electronic properties of spin-coated films of pure 1−6 were investigated with nanoscale resolution by Kelvin probe force microscopy (KPFM). KPFM measurements showed that charge generation and separation were obtained for all films under illumination. Consequently, 1−6 were tested on single-material organic solar cells (SMOCs). In agreement with KPFM results, photovoltaic behavior was observed for all compounds with power conversion efficiencies in line with the best results obtained so far for the few donor−acceptor molecules already shown to perform in single-component solar cells. To our knowledge, this is the first time in which thiophene−benzothiadiazole co-oligomers and copolymers are shown to be photoactive materials in SMOCs. Di Maria, Francesca; Biasiucci, Mariano; Di Nicola, Francesco Paolo; Fabiano, Eduardo; Zanelli, Alberto; Gazzano, Massimo; Salatelli, Elisabetta; Lanzi, Massimiliano; Della Sala, Fabio; Gigli, Giuseppe; Barbarella, Giovanna Di Maria, Francesca; Biasiucci, Mariano; Di Nicola, Francesco Paolo; Fabiano, Eduardo; Zanelli, Alberto; Gazzano, Massimo; Salatelli, Elisabetta; Lanzi, Massimiliano; Della Sala, Fabio; Gigli, Giuseppe; Barbarella, Giovanna

In this work, we explore the effects of the ultrastrong coupling regime between light and molecular excitons on the electrical and optical properties of microcavity-OLEDs. We studied two different samples having a coupling value of 31% and 48%. The main effect of the ultrastrong interaction is on the electroluminescent emission linewidth which was only 28 meV, that is about 12-fold narrower than that of the corresponding photoluminescence of the uncoupled material and even half the linewidth of photonic (weak-coupled) microcavity working at the same wavelength.

The matrix assisted pulsed laser evaporation (MAPLE) technique is emerging as an alternative route to conventional deposition methods of organic materials (solution-phase and thermal evaporation approaches). However, the high surface roughness of the films deposited by MAPLE makes this technique not compatible with applications in electronics and photonics. In this paper we report the deposition of MAPLE-films of a green light emitting polymer, commercially named ADS125GE, with remarkable low roughness values, down to about 10 nm at the thickness conventionally used in photonic devices (similar to 40 nm). This issue is discussed as a function of polymer concentration, target-substrate distance and substrate rotation based on AFM topography images, roughness estimation and optical (absorption and luminescent) measurements. In addition we have fabricated an organic light emitting diode with this technique using the best deposition parameters which guarantee the lowest roughness. These results open the way to MAPLE applications in organic photonics and opto-electronics.

A spectroscopic investigation focusing on the charge generation and transport in inverted p-type perovskite-based mesoscopic (Ms) solar cells is provided in this report. Nanocrystalline nickel oxide and PCBM are employed respectively as hole transporting scaffold and hole blocking layer to sandwich a perovskite light harvester. An efficient hole transfer process from perovskite to nickel oxide is assessed, through time-resolved photoluminescence and photoinduced absorption analyses, for both the employed absorbing species, namely MAPbI(3-x)Cl(x) and MAPbI(3). A striking relevant difference between p-type and n-type perovskite-based solar cells emerges from the study.

Here we conceive an innovative nanocomposite to endow hybrid perovskites with the easy processability of polymers, providing a tool to control film quality and material crystallinity. We verify that the employed semiconducting polymer, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), controls the self-assembly of CH3NH3PbI3 (MAPbI(3)) crystalline domains and favors the deposition of a very smooth and homogenous layer in one straightforward step. This idea offers a new paradigm for the implementation of polymer/perovskite nanocomposites towards versatile optoelectronic devices combined with the feasibility of mass production. As a proof-of-concept we propose the application of such nanocomposite in polymer solar cell architecture, demonstrating a power conversion efficiency up to 3%, to date the highest reported for MEH-PPV. On-purpose designed polymers are expected to suit the nanocomposite properties for the integration in diverse optoelectronic devices via facile processing condition.

The excellent luminescence and gain properties of substituted oligothiophenes are exploited to imprint one-dimensional photonic crystals for the fabrication of printed distributed feedback (DFB) cavities. We demonstrate the dry-printing of organic semiconductor lasers, carrying out the realization of a complete device by a single nanofabrication step, which can be perfectly integrated with other existing planar semiconductor processing and etching technologies. In particular, a thiophene-based pentamer with very good amplified spontaneous emission and optical gain properties was used to fabricate a single-mode, first-order DFB lasers exhibiting an emission with a linewidth of 1.1 nm at about 636 nm for excitation fluences larger than 27 μJ/cm 2 . These results clearly indicate that substituted oligothiophene- S , S - dioxides are promising candidates for solid-state lasers realizable by emerging nanopatteming technologies.

Oligomer molecules offer a number of advantages for the study of their photo-physical properties and for the application to optoelectronic devices. We investigated the optical properties of a substituted quinquethiophene by first-principles calculations, determining the absorption and the emission energies, and compared these to the experimental data. The optical gain properties of the oligomer were exploited for the realization of a solid-state laser device exhibiting single-mode emission at 637 nm , with a full-width half-maximum of about 0.7 nm and a pump fluence threshold as low as 220 μJ / cm 2 .

We investigated the gain properties of spin coated films of a soluble substituted quinque-thiophene under ns pulsed optical excitation. The oligomer exhibits a clear line narrowing, due to amplified spontaneous emission assisted by waveguiding film slab, for excitation fluences larger than 0.8 mJ cm−2. The oligothiophene was employed as the active medium of different organic resonators. In particular, we report about directly printed organic distributed-feedback resonators, exploiting the one-dimensional periodic modulation of the organic surface. The devices exhibit single-mode emission between 630 and 640 nm, with a full width half maximum of about 1 nm and a pump threshold as low as 140 μJ/cm2 at room temperature. These results make the substituted oligothiophenes excellent candidates as active media of optically-confined nanostructures. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Novel co-sensitizers have been structurally tailored and implemented in multi-sensitized devices demonstrating synergic efficiency enhancement attributable to improved light-harvesting as well as prevention of charge recombination. This journal is © the Partner Organisations 2014.

A photovoltachromic window can potentially act as a smart glass skin which generates electric energy as a common dye-sensitized solar cell and, at the same time, control the incoming energy flux by reacting to even small modifications in the solar radiation intensity. We report here the successful implementation of a novel architecture of a photovoltachromic cell based on an engineered bifunctional counter electrode consisting of two physically separated platinum and tungsten oxide regions, which are arranged to form complementary comb-like patterns. Solar light is partially harvested by a dye-sensitized photoelectrode made on the front glass of the cell which fully overlaps a bifunctional counter electrode made on the back glass. When the cell is illuminated, the photovoltage drives electrons into the electrochromic stripes through the photoelectrochromic circuit and promotes the Li+ diffusion towards the WO3 film, which thus turns into its colored state: a photocoloration efficiency of 17 cm(2) min(-1) W-1 at a wavelength of 650 nm under 1.0 sun was reported along with fast response (coloration time

In this work, we report on similar to 4% power conversion efficiency (PCE) depleted bulk heterojunction (DBH) solar cells based on a high-quality electrode with a three-dimensional nanoscale architecture purposely designed so as to maximize light absorption and charge collection. The newly conceived architecture comprises a mesoporous electron-collecting film made of networked anisotropic metal-oxide nanostructures, which accommodates visible-to-infrared light harvesting quantum dots within the recessed regions of its volume. The three-dimensional electrodes were self-assembled by spin-coating a solution of colloidal branched anatase TiO2 NCs (BNC), followed by photocatalytic removal of the native organic capping from their surface by a mild UV-light treatment and filling with small PbS NCs via infiltration. The PCE similar to 4% of our TiO2 BNC/PbS QD DBH solar cell features an enhancement of 84% over the performance obtained for a planar device fabricated under the same conditions. Overall, the DBH device fabrication procedure is entirely carried out under mild processing conditions at room temperature, thus holding promise for low-cost and large-scale manufacturing.

An explorative dye solar cell architecture based on the implementation of a 3D micropatterned photoelectrode is disclosed here. An array of conical micropillars has been realized by laser micromachining of photosensitive glass which has been advantageously used as a substrate for deposition of a thin transparent conductive layer and a thick mesoporous TiO2electrode. A significantly higher photocurrent density has been detected as an effect of the extended overall absorbing area of the micropatterned photoelectrode with respect to a conventional 2D reference photoelectrode. This enhancement can also be partially imputable to a not negligible “waveguide effect” occurring within the glass micropillars.

A new architecture for multifunctional photoelectrochemical devices, namely photovoltachromic devices, is disclosed here, capable of producing electric energy by solar conversion also modulating the devices' optical transmittance in a smart and aesthetically sounding fashion. These devices generally consist of a titanium dioxide photoelectrode and of a bifunctional patterned counter electrode made of platinum and amorphous tungsten oxide. The innovative configuration described hereafter proposes to split the single patterned counter electrode into two distinct electrodes, physically overlapped: the central one is suitably drilled in order to allow the electrolyte to fill both communicating chambers. These three electrode devices allow three independent operating modes: photovoltaic, photoelectrochromic, and photovoltachromic. In this paper, we report the optical, electrical, and electrochemical characterization of this innovative device, varying both available catalytic surface area and the type of sensitizing dye. We eventually obtained the following conversion efficiencies, 2.75%, 2.35%, and 1.91%, in samples having different catalytic areas (397, 360, and 320 mm(2), respectively). We inferred that the higher the platinum area on the interposed platinum-poly(ethylene naphthalate)-indium tin oxide counter electrode, the higher the photovoltaic conversion efficiency. On the other hand, a decrease of the intercommunication openings generates a slowdown of bleaching processes.

An organic based microcavity showing fully reversible colour tunability has been achieved for the first time. The emission output changes according to the modulation from pure photonic to polaritonic resonant modes through UV irradiation of the light-switchable matrix.

We report photo and electroluminescence efficiency of a thiophene oligomer functionalized to enhance its solid-state efficiency. We find that the absolute PL quantum yield is up to 37% for spin-coated thin films of the compound. The material has been used as active material in organic light-emitting diodes (LEDs). EL efficiencies up to 0.9 cd/A are demonstrated in LEDs prepared with a blend indium tin oxide and Ca–Al electrodes.

We report a double emission layer structure, incorporating a double phosphorescent ldquoguest/host systemrdquo of tris (1-Phenylisoquinoline) iridium (III) (Ir(piq)3) 15wt% doped into two different host molecules, 4,4'-bis[N-(1-napthyl)-N-phenyl-amino] biphenyl (NPB) and bis-(2-methyl-8-quinolinolato)-4-(phenyl-phenolato) aluminum-(III) (BAlq). The proposed configuration reduces the efficiency rolloff, providing high stability at high operating luminance. A maximum current efficiency of 9.5 cd/A, at a driving voltage of 3 V, and a remarkably long device lifetime of more than 2500 h at a starting luminance of 6000 cd/m2 have been measured.

An engineered bi-layered photoelectrode fordyesolar cells has been developed which profitably employs two synergistic meso-ordered components, namely a thin meso-ordered TiO2film and a main microparticles-based photoelectrode. The former has been deposited as an interfacial layer at the FTO-coated substrate and suppresses the back-transport reaction by blocking direct contact between the electrolyte and conductiveoxide. The latter is made of hierarchical micro- and nano-structured building blocks prepared by template synthesis, which permits efficient light scattering without sacrificing the internal surface area. The optimization of light harvesting and charge recombination dynamics allowed us to achieve as high energy conversion efficiency as 9.7%.

We have developed a room-temperature solution processing approach to integrate colloidal anatase titanium dioxide nanorods (TiO2 NRs) and lead sulfide quantum dots (PbS QDs) into a heterostructured p-n junction device. To this aim we have exploited a post-deposition treatment to remove surface-adsorbed ligands by means of UV-light-irradiation of TiO2 NRs and a dilute acid treatment of PbS QDs. Here we report a systematic study on the optimization of the post-deposition treatments and device fabrication. Our approach is fully compatible with plastic device technology and is potentially useful for the integration of crystalline TiO2 as active component into disparate solar cell architectures and organic optoelectronic devices. © 2013 Elsevier B.V. All rights reserved.

The technology of white organic light-emitting diodes (WOLEDs) is attracting growing interest due to their potential application in indoor lighting. Nevertheless the simultaneous achievement of high luminous efficacy (LE), high color rendering index (CRI), very low manufacturing costs and compatibility with flexible thin substrates is still a great challenge. Indeed, very high efficiency devices show usually low values of CRI, not suitable for lighting applications, and use expensive indium tin oxide (ITO) electrodes which are not compatible with low cost and/or flexible products. Here we show a novel low cost ITO-free WOLED structure based on a multi-cavity architecture with increased photonic mode density and still broad white emission spectrum, which allows for simultaneous optimization of all device characteristics. Without using out-coupling optics or high refractive index substrates, CRI of 85 and LE as high as 33 lm W-1 and 14 lm W-1 have been demonstrated on ITO-free glass and flexible substrates, respectively. (C) 2013 Elsevier Ltd. All rights reserved.

A highly dense and uniform layer of Au nanoparticles (NPs) on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film has been produced by the pulsed laser deposition (PLD) technique toward the production of an improved efficiency photovoltaic device. The advantage of PLD over other techniques is the easy and precise control of the Au NPs size and spatial distribution, without needing of further NP surface functionalization. The efficiency enhancement factor related to Au NPs doping has been evaluated in a solar cell based on poly-(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) diffused bilayer. The short-circuit current density, J SC, increases by 18 % and the power conversion efficiency by 22 %, respectively, in comparison with an equivalent device without Au NPs. The optical and morphological properties of the Au NPs layer have been selected in order to evaluate the contribution of the surface plasmon resonance as enhancement factor of the solar cell efficiency, in a range size where light scattering is negligible.

An engineered photoelectrode for dye solar cells has been developed through the combination of three mesoporous stacks made of shape-tailored TiO2 anatase nanocrystals, which have been ad hoc synthesized by suitable colloidal routes. Optimization of light harvesting and charge collection efficiency allowed us to obtain a high power conversion efficiency of 10.26%.

The donor/acceptor inter-mixing in bulk heterojunction (BHJ) solar cells is a critical parameter, often leading to irreproducible performance of the finished device. An alternative solution-processed device fabrication strategy towards a better control of the micro/nano-structured morphology consists of a sequential coating of the donor (e.g., poly-(3-hexylthiophene), P3HT) and the acceptor (e.g., [6,6]-phenyl-C61-butyric acid methyl ester, PCBM) from orthogonal solvents. We demonstrate that, in spite of the solvent orthogonality, this technique does not lead to a well-defined bilayer with a sharp interface, but it rather results in a graded vertical phase-separated junction, resulting from the diffusion of the PCBM in the P3HT bottom layer. We are able to control the diffusion of PCBM, which occurs preferentially in the amorphous P3HT domains, by easily varying the ratio between crystalline/amorphous domains in the P3HT. Such a ratio can be simply modified by changing the solvent for P3HT. We show that the donor–acceptor diffused bilayer (DB) junction is an intermediate structure which combines both advantages of the well-defined bilayer and conventional BHJ configurations. Indeed, the DB device geometry ensures the good reproducibility and charge percolation, like the well-defined bilayer, while preserving the interpenetration of the donor and acceptor species, resulting in an efficient charge separation, characteristic of the BHJ. Overall the annealed DB device geometry can be assimilated to a graded BHJ with an improved reproducibility and mean power conversion efficiency (PCE) of 3.45%, higher than that of the standard BHJ devices of 3.07%. Furthermore, we demonstrate the highest performance for the as-cast DB device with a PCE of 2.58%. It is worthy to note that our DB device exhibits improved open circuit voltage, fill factor, series and shunt resistances, which denote that the vertically phase separated DB junction ensures improved charge percolation.

The integration of a plasmonic lamellar grating in a heterostructure organic solar cell as a light trapping mechanism is investigated with numerical Finite Elements simulations. A global optimization of all the geometric parameters has been performed. The obtained wide-band enhancement in optical absorption is correlated with both the propagating and the localized plasmonic modes of the structure, which have been identified and characterized in detail. (c) 2012 Optical Society of America