In this study, the effect of electrochemical etching time on the layer thickness, electrical, optical, and physical properties of fluorine-doped tin oxide (FTO) films are reported. The electrochemical etching was carried out for various durations, up to 40 min, using an electrolyte composed of zinc acetate dihydrate dissolved in hydrochloric acid. The etching kinetics, which are defined by the gradual decrease in layer thickness, were thoroughly examined and correlated to the material's electrical, optical, and wetting properties as well as surface chemistry. Surface passivation progressively impedes FTO dissolution, causing the etching rate to decrease exponentially. During the first 5 min of FTO etching, the sheet resistivity and surface energy increased from 13.2 to 109.0 Omega/square and from 27.4 to 29.3 mN/m, respectively, accompanied by a gradual increase in charge-transfer resistance. This indicates the need of an optimized etching time that balances electrical, optical, and surface properties. A detailed analysis of FTO's optical characteristics at various etching periods was conducted. The gradual alterations in the FTO surface chemistry and surface-related characteristics that were dependent on the etching time were primarily responsible for the observed changes in the physical, electrical, wetting, and optical properties. Additionally, a stronger surface-related influence on the charge carrier dynamics and recombination in the perovskite layer was demonstrated by the exponential decline in photoluminescence intensity of the MAPbI3 films on the etched FTO substrates with increasing etching time. This study provides a deeper understanding of the electrochemical etching of FTO and highlights the potential for enhancing its structural, electrical, and wetting properties to improve performance in optoelectronic devices.

The noticeable growth in the power conversion efficiency of solution-processed organo-inorganic halide perovskite solar cells (OIHPSCs) incited the photovoltaic community to look for limitations that hurdle the commercialization process. The surface and interface defects between the perovskite and electron transport layers are among the main challenges that cause significant non-radiative recombination losses, thereby they result in poor performance and stability. In this work, tetracyanoquinodimethane (TCNQ), a strong electron acceptor molecule, is applied at the interface between the photoactive perovskite and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) layers to modify the interface, and enhance device performance and stability. Steady-state and time-resolved photoluminescence measurements were used to characterize the role of the TCNQ passivation in reducing non-radiative recombination of charge carriers. Current density versus voltage (J-V) measurements show improvement in devices open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF) for devices with TCNQ interface passivation, which is attributed to suppressed non-radiative recombination. In addition, a noticeable improvement in the device’s stability was observed. This study reveals the dual role of TCNQ passivation in improving the photoelectric properties and stability of ambient air processed perovskite devices with the pin architecture.

Noble metal nanoparticles are known to act as redox catalysts or cocatalysts in important reactions including water splitting, nitrogen fixation, or CO2 reduction. In case their diameter falls below about 10 nm, the literature is split between, on the one hand, reports of ever-increasing catalytic activity with decreasing diameter and, on the other hand, reports about an optimal diameter of about 3-6 nm, below which the catalytic activity decreases rapidly. In our study, we use the model reduction of ferricyanide to ferrocyanide catalyzed by gold nanoparticles to demonstrate that, determined by the oxidative counter-reaction, different dependencies of the catalytic activity on diminishing nanoparticle diameter exist. If no intermediate charge storage takes place, the catalytic activity increases monotonically roughly with the inverse of the diameter, down to 2 nm. If, however, a strong reductant is present, the nanoparticles act as an intermediate storage of electrons, so-called nanocathodes, which is compromised by Coulomb repulsion. This leads to an optimal diameter of 4-5 nm. It is the strength of this study that exactly the same batches of gold nanoparticles and the same model reduction are used so that the parameter space for the different size dependence of the catalytic activity is limited to the differences in oxidative counter-reactions.

As photosensitizers for harvesting solar energy, dyes play a major role in the operation and photochemical performance of dye-sensitized solar cells (DSSCs). DSSCs are usually fabricated using non-biodegradable, synthetic dyes, which often contain toxic heavy metals. However, replacing synthetic dyes with cheap and biodegradable natural dyes can produce cost-effective and eco-friendly DSSCs. In this study, we investigate the suitability of natural dye extracts of Vernonia amygdalina, Goeppertia macrosepala leaves and Cnestis ferruginea fruit as photosensitizers in DSSCs. The influence of solvents on the performance of these three natural dye extracts is also examined. The natural dyes are extracted using acetone and ethanol solvents and characterized by Fourier-transform infrared (FTIR), UV–Vis, and photoluminescence (PL) spectroscopy. The FTIR spectrometry results for all the dye samples demonstrate the presence of three functional groups: the hydroxyl, amine, and carbonyl groups, a strong indication of good adsorption by the semiconductor metal oxides in DSSCs. The UV-Vis and PL spectra show that the natural dyes of V. amygdalina, G. macrosepala, and C. ferruginea extracted with acetone and ethanol exhibit stable and strong optical absorption in the visible region of the electromagnetic spectrum. Thus, the three natural dyes examined are potential candidates for photosensitizers in DSSCs. The DSSC fabricated with V. amygdalina dye extracted using acetone delivers the highest solar conversion efficiency with performance parameters Jsc, Voc, FF, and η as 330.51 µA/cm2, 522 mV, 0.7, and 0.12

This study presents molecular boron subphthalocyanine complex precursors ((Cl-B-SubPc) 1 and (Cl-B-SubPc-OC12H23) 2) designed for efficient CO2 reduction. The resulting heterogeneous catalysts exhibit remarkable total faradaic efficiencies of up to 98%, integrated into practical cell assemblies. Optimizations encompass not only catalyst design but also operational conditions, facilitating prolonged CO2 electrolysis across various current densities. Varied C1-, C2-, and C3-product yields are observed at different reductive potentials, with electrocatalysis experiments conducted up to 200 mA cm-2. Comparative electrochemical analyses across H-cell and zero-gap cell electrolyzers show the potential for industrial scale-up. Mechanistic elucidation via in situ UV-vis spectroelectrochemistry, DFT calculations, and ESR spectroscopy demonstrates the involvement of boron N-C sites, initiating radical formation and utilizing boron's Lewis acid behavior in CO2 capture, followed by proton-coupled electron transfer. Overall, the study underscores the transformative potential of boron subphthalocyanine systems in advancing CO2 utilization technologies.

Hydrogen peroxide (H2O2) is identified as a promising reagent for fuel cells, reducing the dependency on carbon-based fuels. In this work, electrochemically synthesized polymers are employed to improve the efficiency of the oxygen (O2) reduction reaction, thus producing H2O2 in an environmentally friendly way. Two aminoanthraquinones, as well as riboflavin (vitamin B2), are successfully immobilized via oxidative electropolymerization onto both glassy carbon and carbon paper. Of the investigated compounds, polyriboflavin shows a high Faradaic efficiency toward O2 reduction, even at a very low potential of only -0.1 V versus SHE. This catalytic effect is present in neutral and alkaline conditions, using both glassy carbon and carbon paper, but highly pronounced in neutral, aqueous solutions. Two aminoanthraquinones, as well as riboflavin (vitamin B2), are immobilized via oxidative electropolymerization onto both glassy carbon and carbon paper. Polyriboflavin shows a high Faradaic efficiency toward O2 reduction, even at a low potential of -0.1 V versus SHE. This catalytic effect is present in neutral and alkaline conditions.image

Emerging photovoltaic (PV) technologies are considered to be excellent candidates to be used as power sources for indoor and low‐light applications. The already demonstrated high power conversion efficiencies (PCEs) and the potential to manufacture perovskite, organic, or dye‐sensitized solar cells at low cost make them particularly interesting. In this work, the maximum PCE of PV devices under low‐light conditions is explored. The role of spectral mismatch, non‐radiative recombination, and parasitic Ohmic losses is investigated. The performed calculation provides guidelines to improve the low‐light performance of PV devices for ambient light. In addition, a simple measurement procedure for the indoor PCE is discussed.

Perovskite solar cells are a promising technology for emerging photovoltaic applications that require mechanical compliance and high specific power. However, the devices suffer from poor operational stability. Here we develop lightweight, thin (<2.5 mu m), flexible and transparent-conductive-oxide-free quasi-two-dimensional perovskite solar cells by incorporating alpha-methylbenzyl ammonium iodide into the photoactive perovskite layer. We fabricate the devices directly on an ultrathin polymer foil coated with an alumina barrier layer to ensure environmental and mechanical stability without compromising weight and flexibility. We demonstrate a champion specific power of 44 W g(-1) (average: 41 W g(-1)), an open-circuit voltage of 1.15 V and a champion efficiency of 20.1% (average: 18.1%). To show scalability, we fabricate a photovoltaic module consisting of 24 interconnected 1 cm(2) solar cells and demonstrate energy-autonomous operation of a hybrid solar-powered quadcopter, while constituting only 1/400 of the drone's weight. Our performance and stability demonstration of ultra-lightweight perovskite solar cells highlight their potential as portable and cost-effective sustainable energy harvesting devices.

The development of ambient-air-processable organic-inorganic halide perovskite solar cells (OIHPSCs) is a challenge necessary for the transfer of laboratory-scale technology to large-scale and low-cost manufacturing of such devices. Different approaches like additives, antisolvents, composition engineering, and different deposition techniques have been employed to improve the morphology of the perovskite films. Additives that can form Lewis acid-base adducts are known to minimize extrinsic impacts that trigger defects in ambient air. In this work, we used the 3-thiophenemalonic acid (3-TMA) additive, which possesses thiol and carboxyl functional groups, to convert PbI2, PbCl2, and CH3NH3I to CH3NH3PbI3 completely. This strategy is effective in regulating the kinetics of crystallization and improving the crystallinity of the light-absorbing layer under high relative humidity (RH) conditions (30-50%). As a result, the 3-TMA additive increases the yield of the power conversion efficiency (PCE) from 14.9 to 16.5% and its stability under the maximum power point. Finally, we found that the results of this work are highly relevant and provide additional inputs to the ongoing research progress related to additive engineering as one of the efficient strategies to reduce parasitic recombination and enhance the stability of inverted OIHPSCs in ambient environment processing.

The advanced development of optoelectronic devices requires a methodical knowledge of the fundamental material properties of the key active components. Systematic investigations and correlations of such basic optical properties can lead to new insights for the design of more potent materials. In this perspective, we provide a systematic overview of the uniaxial anisotropic complex refractive indices and the absorption coefficients obtained by ellipsometry as well as the optical band gap energies derived from Tauc plots of six selected solution-processed polymer thin films. While the optical band gap energies are intentionally distributed over the visible spectral range, we found that the absorption strength of all polymer samples are grouped in a random distribution within a rather uniform range of values.

AbstractThe unprecedented increase in power conversion efficiency (PCE) of low‐cost organo‐inorganic halide perovskite solar cells (OIHPSCs) toward its Shockley‐Queisser limit intriguingly has prompted researchers to investigate the disadvantages of these devices. The issue of operational stability is the main hurdle challenging the way forward for commercialization. To address this, various engineering processes like composition, additives, anti‐solvents, bulk and interface passivation, and deposition techniques have been widely applied to manage both extrinsic and intrinsic factors that induce degradation of the OIHPSCs. In this work, we employed interface passivation, which is an efficient approach to reduce nonradiative recombination. An ultrathin layer of electron donor diketopyrrolopyrrole‐oligothiophene copolymer (DPP860) was applied as an interface passivator between the photoactive layer and [6,6]‐phenyl C61 butyric acid methyl ester (PCBM). The role of the interface passivation on optoelectronic properties of the OIHPSCs was assessed using current density versus voltage (J‐V) characteristics, photoluminescence spectroscopy and time‐resolved photoluminescence spectroscopy. The findings show devices treated with DPP860 exhibit enhanced current density (Jsc) and fill factor, attributing for suppressed nonradiative recombination. Moreover, it shows relative improvement in the stability of the device. The results of this finding reveal that using oligothiophene copolymer can enhance the photovoltaic performance and the stability of inverted OIHPSCs in the ambient environment.

Using the reverse micelle synthesis route, polystyrene-b-2vinylpyridine (PS-b-P2VP) diblock copolymers are used to synthesize hybrid perovskite nanoparticles with an ionic organic liquid five-membered heterocycle cation, pyrrolidinium (Py) (C4H8NH). Uniform, well-dispersed, and luminescent nanoparticles were fabricated with high stability due to the hydrophobic nature of Py and polymer encapsulation. The substitution of bromine for iodine induces a bathochromic shift, resulting in a substantial Stokes shift of 764 meV (211 nm) for mixed halide phase nanoparticles, contrary to the anticipated hypsochromic shift with bromine doping. This unique attribute of Py-based perovskites positions them as promising candidates for down-conversion applications in low-band-gap organic solar cells. Incorporating Py-based perovskite nanoparticles into bulk heterojunction organic photovoltaics (OPVs) as down-conversion layers selectively enhances the short-circuit current from UV components in the illumination source. The observed improvements in stability, uniformity, and luminescence, coupled with the distinct Stokes shift, underscore the potential of Py-based perovskite nanoparticles as a valuable component in improving the efficiency of OPVs.

Thin-film organic photovoltaic (OPV) devices represent an attractive alternative to conventional silicon solar cells due to their lightweight, flexibility, and low cost. However, the relatively low optical absorption of the OPV active layers still represents an open issue in view of efficient devices that cannot be addressed by adopting conventional light coupling strategies derived from thick PV absorbers. The light coupling to thin-film solar cells can be boosted by nanostructuring the device interfaces at the subwavelength scale. Here, we demonstrate broadband and omnidirectional photon harvesting in thin-film OPV devices enabled by highly ordered one-dimensional (1D) arrays of nanogrooves. Laser interference lithography, in combination with reactive ion etching (RIE), provides the controlled tailoring of the height and periodicity of the silica grooves, enabling effective tuning of the anti-reflection properties in the active organic layer (PTB7:PCBM). With this strategy, we demonstrate a strong enhancement of the optical absorption, as high as 19% with respect to a flat device, over a broadband visible and near-infrared spectrum. The OPV device supported on these optimized nanogrooved substrates yields a 14% increase in short-circuit current over the corresponding flat device, highlighting the potential of this large-scale light-harvesting strategy in the broader context of thin-film technologies.

AbstractSurface‐enhanced Raman scattering (SERS) is a sensitive and fast technique for sensing applications such as chemical trace analysis. However, a successful, high‐throughput practical implementation necessitates the availability of simple‐to‐use and economical SERS substrates. In this work, we present a robust, reproducible, flexible and yet cost‐effective SERS substrate suited for the sensitive detection of analytes at near‐infrared (NIR) excitation wavelengths. The fabrication is based on a simple dropcast deposition of silver or gold nanomaterials on an aluminium foil support, making the design suitable for mass production. The fabricated SERS substrates can withstand very high average Raman laser power of up to 400 mW in the NIR wavelength range while maintaining a linear signal response of the analyte. This enables a combined high signal enhancement potential provided by (i) the field enhancement via the localized surface plasmon resonance introduced by the noble metal nanomaterials and (ii) additional enhancement proportional to an increase of the applicable Raman laser power without causing the thermal decomposition of the analyte. The application of the SERS substrates for the trace detection of melamine and rhodamine 6G is demonstrated, which shows limits of detection smaller than 0.1 ppm and analytical enhancement factors on the order of 104 as compared to bare aluminium foil.

Perylene monoimide based electron acceptors have great properties for use in organic solar cells, like thermal stability, strong absorption, and simple synthesis. However, they typically exhibit low values for the dielectric permittivity. This hinders efficient exciton dissociation, limiting the achievable power conversion efficiencies. In this work, we present the synthesis and utilization of two new acceptor–donor-acceptor (A-D-A) molecules, comprising perylene monoimide as electron withdrawing A unit. Oligo ethylene glycol side chain modified carbazole (PMI-[C-OEG]) and fluorene (PMI-[F-OEG]) linkers were used as electron rich D units, respectively. The polar side chains are expected to increase the polarizability of the molecules and, thus, their permittivity according to the Clausius–Mossotti relationship. We found that the incorporation of glycol chains improved the dielectric properties of both materials in comparison to the reference compounds with alkyl chains. The permittivity increased by 18

Terminal acceptor atoms and side-chain functionalization play a vital role in the construction of efficient nonfullerene small-molecule acceptors (NF-SMAs) for AM1.5G/indoor organic photovoltaic (OPV) applications. In this work, we report three dithienosilicon-bridged carbazole-based (DTSiC) ladder-type (A-DD'D-A) NF-SMAs for AM1.5G/indoor OPVs. First, we synthesize DTSiC-4F and DTSiC-2M, which are composed of a fused DTSiC-based central core with difluorinated 1,1-dicyanomethylene-3-indanone (2F-IC) and methylated IC (M-IC) end groups, respectively. Then, alkoxy chains are introduced in the fused carbazole backbone of DTSiC-4F to form DTSiCODe-4F. From solution to film absorption, DTSiC-4F exhibits a bathochromic shift with strong π-π interactions, which improves the short-circuit current density (Jsc) and the fill factor (FF). On the other hand, DTSiC-2M and DTSiCODe-4F display up-shifting lowest unoccupied molecular orbital (LUMO) energy levels, which enhances the open-circuit voltage (Voc). As a result, under both AM1.5G/indoor conditions, the devices based on PM7:DTSiC-4F, PM7:DTSiC-2M, and PM7:DTSiCOCe-4F show power conversion efficiencies (PCEs) of 13.13/21.80%, 8.62/20.02, and 9.41/20.56%, respectively. Furthermore, the addition of a third component to the active layer of binary devices is also a simple and efficient strategy to achieve higher photovoltaic efficiencies. Therefore, the conjugated polymer donor PTO2 is introduced into the PM7:DTSiC-4F active layer because of the hypsochromically shifted complementary absorption, deep highest occupied molecular orbital (HOMO) energy level, good miscibility with PM7 and DTSiC-4F, and optimal film morphology. The resulting ternary OSC device based on PTO2:PM7:DTSiC-4F can improve exciton generation, phase separation, charge transport, and charge extraction. As a consequence, the PTO2:PM7:DTSiC-4F-based ternary device achieves an outstanding PCE of 13.33/25.70% under AM1.5G/indoor conditions. As far as we know, the obtained PCE results under indoor conditions are one of the best binary/ternary-based systems processed from eco-friendly solvents.

Hybrid organic-inorganic perovskite photovoltaic has achieved unmatched power conversion efficiency (PCE) improvement in the last decade. Nevertheless, nonradiative recombination of charge carriers due to bulk and interface defects reduces the open-circuit voltage (V-oc) and PCE of perovskite solar cells. Incorporating additives, process optimization, and interface engineering are among the effective approaches employed to reduce such issues. Herein, quasi-2D p-i-n perovskite solar cells incorporating alpha-methylbenzyl ammonium iodide (MBAI) cation with outstanding photovoltaic performance and stability are developed. MBAI incorporation results in films with excellent optical and electrical properties, leading to higher V-OC of approximate to 1.15V, fill factor of above 77%, and stability of the device. A high open-circuit voltage and fill factor and corrected power conversion efficiencies in the range of 15% are obtained for the prepared devices. The encapsulated solar cells show excellent operational stability under white light illumination in ambient air for >500h. Due to the simple and robust preparation process, the investigated inverted perovskite solar cell can easily be combined with other solution-processed thin film solar cells to form multijunction devices and can easily be integrated into different lightweight and flexible products.

Alkoxy side chain engineering on the beta-position of the thienothiophene units of Y6 derivatives plays a vital role in improving photovoltaic performances with simultaneously increasing open-circuit voltage (V-oc) and fill factor (FF). In this work, we prepared a series of asymmetric non-fullerene acceptors (NFAs) by introducing alkoxy side chains and phenoxy groups on the state-of-the-art Y6-derivative BTP-BO-4F. For the comparison, 2O-BO-4F with a symmetric alkoxy side chain on the outer thiophene units and BTP-PBO-4F with an asymmetric N-attached phenoxy alkyl chain on the pyrrole ring are synthesized from BTP-BO-4F. Thereafter, we construct four asymmetric NFAs by introducing different lengths of linear/branched alkoxy chains on the beta-position of the thienothiophene units of BTP-PBO-4F. The resulting NFAs, named L10-PBO, L12-PBO, B12-PBO, and B16-PBO (L = linear and B = branched alkoxy side chains), are collectively called OR-PBO-series. Unexpectedly, all OR-PBO NFAs exhibit strong edge-on molecular packing and weaker pi-pi interactions in the film state, which diminish the charge transfer in organic solar cell (OSC) devices. As a consequence, the optimal devices of OR-PBO-based binary blends show poor photovoltaic performances [power conversion efficiency (PCE) = 6.52-9.62%] in comparison with 2O-BO-4F (PCE = 12.42%) and BTP-PBO-4F (PCE = 15.30%) reference blends. Nevertheless, the OR-PBO-based binary devices show a higher V-oc and smaller V-loss. Especially, B12-PBO- and B16-PBO-based devices achieve V-oc over 1.00 V, which is the highest value of Y-series OSC devices to the best of our knowledge. Therefore, by utilizing higher V-oc of OR-PBO binary blends, B12-PBO and B16-PBO are incorporated into the PM6:BTP-PBO-4F-based binary blend and fabricated ternary devices. As a result, the PM6:BTP-PBO-4F:B12-PBO ternary device delivers the best PCE of 15.60% with an increasing V-oc and FF concurrently.

Perovskite Solar Cells In article 2208061, Lukas E. Lehner, Martin Kaltenbrunner, and co-workers report the controlled nucleation of quasi-2D perovskites at the liquid–air interface of the precursor solution. Restricting the initial crystal growth to the surface of the liquid results in highly aligned perovskite thin films with improved charge transport, enabling efficient solar cells with excellent stability.

Wide-band gap absorber materials are prerequisites for well-performing tandem photovoltaic devices. Especially, perovskites received huge attention due to their tunable band gap and outstanding optoelectronic properties. Although perovskite solar cells are known to be highly efficient, high-open-circuit voltage losses remain a prevalent issue for wide-band gap perovskites. Within this work, we have investigated the application of the cross-linkable fullerene derivative [6,6]-phenyl-C61-butyric styryl dendron ester (c-PCBSD) as a cathodic interlayer in wide-band gap perovskite solar cells. We could obtain increased open-circuit voltage compared to pristine devices, attributed to fast electron transfer between the perovskite and the interlayer. The changed charge carrier dynamics result in a reduction of non-radiative losses, which consequently decreases the open-circuit voltage loss. Graphical abstract