Photoactive System Research Articles

Co-adsorbed self-assembled monolayer enables high-performance perovskite and organic solar cells

Self-assembled monolayers (SAMs) have become pivotal in achieving high-performance perovskite solar cells (PSCs) and organic solar cells (OSCs) by significantly minimizing interfacial energy losses. In this study, we propose a co-adsorb (CA) strategy employing a novel small molecule, 2-chloro-5-(trifluoromethyl)isonicotinic acid (PyCA-3F), introducing at the buried interface between 2PACz and the perovskite/organic layers. This approach effectively diminishes 2PACz’s aggregation, enhancing surface smoothness and increasing work function for the modified SAM layer, thereby providing a flattened buried interface with a favorable heterointerface for perovskite. The resultant improvements in crystallinity, minimized trap states, and augmented hole extraction and transfer capabilities have propelled power conversion efficiencies (PCEs) beyond 25% in PSCs with a p-i-n structure (certified at 24.68%). OSCs employing the CA strategy achieve remarkable PCEs of 19.51% based on PM1:PTQ10:m-BTP-PhC6 photoactive system. Notably, universal improvements have also been achieved for the other two popular OSC systems. After a 1000-hour maximal power point tracking, the encapsulated PSCs and OSCs retain approximately 90% and 80% of their initial PCEs, respectively. This work introduces a facile, rational, and effective method to enhance the performance of SAMs, realizing efficiency breakthroughs in both PSCs and OSCs with a favorable p-i-n device structure, along with improved operational stability.

Solvothermally Grown Oriented WO3 Nanoflakes for the Photocatalytic Degradation of Pharmaceuticals in a Flow Reactor.

Contamination by pharmaceuticals adversely affects the quality of natural water, causing environmental and health concerns. In this study, target drugs (oxazepam, OZ, 17-α-ethinylestradiol, EE2, and drospirenone, DRO), which have been extensively detected in the effluents of WWTPs over the past decades, were selected. We report here a new photoactive system, operating under visible light, capable of degrading EE2, OZ and DRO in water. The photocatalytic system comprised glass spheres coated with nanostructured, solvothermally treated WO3 that improves the ease of handling of the photocatalyst and allows for the implementation of a continuous flow process. The photocatalytic system based on solvothermal WO3 shows much better results in terms of photocurrent generation and photocatalyst stability with respect to state-of-the-art WO3 nanoparticles. Results herein obtained demonstrate that the proposed flow system is a promising prototype for enhanced contaminant degradation exploiting advanced oxidation processes.

Effect of two-fold single-atom substitutions (S, Se; C, N) in band gap engineered donor-acceptor conjugated microporous polymers on the efficient aerobic photooxidation of aryl sulfides.

Substitution of a single atom in a photoactive system is capable of vastly altering its optoelectronic properties leading to the generation of an efficient photocatalyst. In this study, we explore the impact of two-fold single-atom substitutions on the optoelectronic properties and photocatalytic performance of donor-acceptor type conjugated microporous polymers (D-A CMPs). For this, three isostructural triphenylamine (TPA)-based D-A CMPs were synthesized namely PTPA-BT, PTPA-BS, and PTPA-PS containing 2,1,3-benzothiadiazole, 2,1,3-benzoselenadiazole and [1,2,5]selenadiazolo[3,4-c]pyridine as the acceptor moieties, respectively. Firstly, PTPA-BT and PTPA-BS were synthesized using the S to Se single-atom substitution strategy, followed by the synthesis of PTPA-PS employing a second C to N single-atom substitution. The effect of single-atom substitution demonstrated drastic changes in their band gap, conductivity, and charge carrier dynamics, which in turn impacted their photocatalytic activity, although the change in their porosity was not much pronounced. In terms of photocatalytic detoxification of sulfur mustards, the activities of D-A CMPs follow the trend: PTPA-BS > PTPA-PS > PTPA-BT. In comparison with PTPA-BT (containing C, S) and PTPA-PS (containing N, Se), PTPA-BS (containing C, Se) exhibits a higher photocatalytic activity towards the photooxidation of thioanisole with >99% conversion and ∼93% isolated yield under visible-light illumination, which is attributed to its lower interfacial charge transfer resistance, stronger photocurrent response, optimal band gap and higher activity to generate superoxide anion radicals. Therefore, the two-fold single-atom substitution strategy is crucial for optimizing D-A CMPs for the photocatalytic oxidation of aryl sulfides. This approach allows fine-tuning of the optoelectronic properties to enhance photocatalytic efficiency and performance.

Potential energy interpolation with target-customized weighting coordinates: application to excited-state dynamics of photoactive yellow protein chromophore in water.

Interpolation of potential energy surfaces (PESs) can provide a practical route to performing molecular dynamics simulations with a reliability matching a high-level quantum chemical calculation. An obstacle to its widespread use is perhaps the lack of general and optimal interpolation settings that can be applied in a black-box manner for any given molecular system. How to set up the weights for interpolation is one such task, and we still need to diversify the approaches in order to treat various systems. Here, we develop a new interpolation weighting scheme, which allows us to choose the weighting coordinates in a system-specific manner, by amplifying the contribution from specific internal coordinates. The new weighting scheme with an appropriate selection of coordinates is proved to be effective in reducing the interpolation error along the reaction pathway. As a demonstration, we consider the photoactive yellow protein chromophore system, as it constitutes itself as an interesting target that bears long-standing questions related to excited-state dynamics inside protein environments. We build its two-state diabatic interpolated PES with the new weighting scheme. We indeed see the utility of our scheme by conducting nonadiabatic molecular dynamics simulations with the required semi-global PES based on a limited number of data points.

Free base porphyrin-cyanine dye conjugate: synthesis and optical properties.

The covalent combination of a cyanine dye (IR-783) with a tetraphenyl porphyrin unit through an ether linkage results in a photoactive system capable of producing singlet oxygen. The synthesis, characterization and photophysical properties of the resulting novel free base porphyrin-cyanine conjugate named TPPO-IR-783 (TOI) is reported. Excited state properties were studied in various solvents with differing polarity. The fluorescence is strongly solvent dependent, however this is not the case for singlet oxygen phosphorescence, which is only observed in tetrahydrofuran (THF), when comparing 8 different polar, non-polar and medium-polarity solvents. This novel type of porphyrin-cyanine photosensitizer has the ability to produce singlet oxygen and absorbs light at NIR wavelengths.

Achieving an excellent efficiency of 11.57% in a polymer solar cell submodule with a 55 cm2 active area using 1D/2A terpolymers and environmentally friendly nonhalogenated solvents

AbstractThe transition of polymer solar cells (PSCs) from laboratory‐scale unit cells to industrial‐scale modules requires the development of new p‐type polymers for high‐performance large‐area PSC modules based on environmentally friendly processes. Herein, a series of 1D/2A terpolymers (PBTPttBD) composed of benzo[1,2‐b:4,5‐b’]dithiophene (BDT‐F), thieno[3,4‐c]pyrrole‐4,6(5H)‐dione (TPD‐TT), and benzo‐[1,2‐c:4,5‐c’]dithiophene‐4,8‐dione (BDD) is synthesized for nonhalogenated solvent processed PSC submodules. The optical, electrochemical, charge‐transport, and nano‐morphological properties of the PBTPttBD terpolymers are modulated by adjusting the molar ratio of the TPD‐TT and BDD components. PBTPttBD‐75:BTP‐eC11‐based PSC submodules, processed with o‐xylene, achieve a notable PCE of 11.57% over a 55 cm2 active area. This PCE value is among the highest reported using a nonhalogenated solvent over a 55 cm2 active area module. The optimized PSC submodule exhibits minimal cell‐to‐module loss, which can be attributed to the optimized crystallinity of the PBTPttBD‐75:BTP‐eC11 photoactive layer system and favorable film formation kinetics.image

Light-Induced Intramolecular Electron Transfer in a 1D [CuFe] Coordination Polymer Containing the [Fe(C2O4)3]3- Core.

A one-dimensional (1D) ladder-like coordination polymer {NH4[{Cu(bpy)}2(C2O4)Fe(C2O4)3]·H2O}n (1; bpy = 2,2'-bipyridine) containing [Cu(bpy)(μ-C2O4)Cu(bpy)]2+ cationic units linked by oxalate groups of [Fe(C2O4)3]3- building blocks was investigated as a new type of photoactive solid-state system. It exhibits a photocoloration effect when exposed to direct sunlight or UV/vis irradiation. The photochromic properties and mechanism were studied by powder and single-crystal X-ray diffraction, UV/vis diffuse reflectance, IR and electron paramagnetic resonance spectroscopy, magnetization and impedance measurements, and density functional theory calculations. The process of photochromism involves simultaneous intramolecular electron transfers from the oxalate ligand to Fe(III) and to [CuII(bpy)(μ-C2O4)CuII(bpy)]2+, leading to the reduction of the metal centers to the electronic states Fe(II) and Cu(I), accompanied by the release of gaseous CO2.

Photopically Transparent Organic Solar Cells with Tungsten Oxide-Based Multilayer Electrodes.

The tailoring of the average photopic transmittance (APT) of transparent organic solar cells (T-OSCs) has been the greatest challenge in building-integrated photovoltaic applications for future smart solar windows to regulate indoor brightness, maintain a human circadian rhythm, and positively impact human emotions by allowing the observation of the external environment. However, a notorious trade-off exists between the APT and power conversion efficiency (PCE) of T-OSCs, mainly due to the absence of highly conductive and transparent top electrodes, which are a key building block determining the PCE and APT. Herein, we demonstrate a new tungsten oxide (WO3)-based multilayer as a highly conductive and transparent top electrode that provides an excellent APT while maintaining a high PCE in T-OSCs. With the assistance of optical simulation based on a transfer matrix method to calculate the optimum thicknesses of the multilayer electrodes, we achieve the best-performing T-OSC with a PCE of 7.0% and a full device APT of 46.7%, resulting in a high light utilization efficiency of 3.27%, which is superior to that of T-OSCs based on the same photoactive system. Furthermore, superior thermal stability at 85 °C in an N2 atmosphere is observed in WO3-based T-OSCs, maintaining 98% of the initial PCE after about 231 h. Our findings provide new insights into the development of T-OSCs with high efficiency and transparency.

Polymer-derived Ni/SiOC materials structured by vat-based photopolymerization with catalytic activity in CO2 methanation

A new concept for the additive manufacturing of nickel-modified polymer-derived ceramics via vat-based photopolymerization is presented. A photoactive polysiloxane resin system modified by nickel nitrate via methacrylic acid complexation was developed and modified to facilitate vat-based photopolymerization. Through pyrolysis of the Ni-modified preceramic polymer at temperatures between 600 and 800 °C, amorphous SiOC components with well-dispersed Ni nanoparticles can be obtained. The modified polymer and the fabricated structures were characterized by photorheology, thermal analysis, scanning and transmission electron microscopy, optical coherence tomography, and powder X-ray diffraction. In addition, the effect of pyrolysis temperature on specific surface area, crystallinity, and shrinkage was investigated. The developed material systems enable additive manufacturing of porous SiOC structures containing crystalline, uniformly distributed, and bimodally sized Ni nanoparticles, exhibiting catalytic activity suitable for CO2 methanation. The developed printable SiOC/Ni materials represent a promising approach for combining metal-modified polymer-derived ceramic systems and additive manufacturing for prospective catalysis applications.

Phototransduction in a supramolecular cascade: a mimic for essential features of the vision process.

The tailored design of a light-triggered supramolecular cascade results in an artificial machinery that assimilates the transduction of photons into chemical communication and the final release of a neurotransmitter. This is reminiscent of key steps in the natural vision process.

The coupled photocycle of phenyl-p-benzoquinone and Light-Harvesting Complex II (LHCII) within the biohybrid system

The combination of trimeric form of the light-harvesting complex II (LHCII3), a porous graphite electrode (GE), and the application of phenyl-p-benzoquinone (PPBQ), the quinone derivative, allow the construction of a new type of biohybrid photoactive system. The Chl fluorescence decay and voltammetric analyzes revealed that PPBQ impacts LHCII3 proportionally to accessible quenching sites and that PPBQ forms redox complexes with Chl in both ground and excited states. As a result, photocurrent generation is directly dependent on PPBQ-induced quenching of Chl fluorescence. Since PPBQ also undergoes photoactivation, the action of GE-LHCII3-PPBQ depends on the mutual coupling of LHCII3 and PPBQ photocycles. The GE-LHCII3-PPBQ generates a photocurrent of up to 4.5 µA and exhibits considerable stability during operation. The three-dimensional arrangement of graphite scraps in GE builds an active electrode surface and stabilizes LHCII3 in its native form in low-density multilayers. The results indicate the future usability of such designed photoactive device.

Dye-sensitized perovskite/organic semiconductor ternary transistors for artificial synapses

Artificial intelligence (AI) is attractive due to its brain-like working pattern and efficient task processing. Light-stimulated synaptic devices show enormous potential in the field of neuromorphic computing. Here, we develop a kind of optical synaptic devices with a ternary photoactive material system consisting of organometal halide perovskite CH3NH3-PbBr3, organic dye Rhodamine B (RhB), and organic semiconductor pentacene. We found that the introduction of RhB can significantly improve the light absorption and photo-responsivity of the composite devices. The devices exhibit acceptable synaptic behaviors and realize a brain-like learning pattern toward various input signals. Notably, the devices can respond to light signals with a low intensity of 1.1 µW cm−2 and be operated at low working voltages. The devices achieve a low energy consumption of 1.25 fJ at a drain-source voltage of −50 µV, comparable to that of a biological synaptic event. Moreover, the devices simulate a self-learning process, indicating their significantly improved learning efficiency. Also, the devices can recognize subtle differences in Morse codes, showing potential in the practical application of information encryption. The excellent optoelectronic performance demonstrates that the proposed ternary synaptic devices are advantageous in developing new AI.

Photoelectrochemical biosensor for DNA formylation based on WS2 nanosheets@polydopamine and MoS2 nanosheets

The photoresponse ability of MoS2 was excellently improved by polydopamine (PDA) coated WS2 composite (WS2@PDA) based on the matched energy band and solid electron donor property of PDA, which significantly blocked the recombination of photogenerated electron-hole pair. Taking the enhanced photoactivity performance of MoS2 and WS2@PDA compound, a simply and sensitively photoelectrochemical biosensor was developed for DNA formation detection, where DNA fragment with 5-formylcytosine (5fC-DNA) was employed as detection target. In the photoactive system, PDA was used as photoactive accelerant and 5fC recognized reagent. After immobilization of MoS2/WS2@PDA, the DNA fragment containing 5-formylcytosine was further captured through the formation of amide bond between the –NH2 of PDA and the –CHO of 5fC, causing the decreased photocurrent due to the electrostatic repulsion effect of negative DNA to photogenerated electron. The biosensor in this work presented wide linear range for 5fC-DNA detection from 0.005 to 200 nM with low detection limit of 3.7 pM (3σ). The developed method not only showed good detection selectivity, but also can discriminate cytosine, 5-methylcitosine and 5-hydroxymethylcytosine to increase its specificity. The applicability of this work was demonstrated by investigating the effect of environmental pollutants on 5fC expression in genomic DNA of maize and wheat seedling leaves respectively.

An efficient photocatalyst based on H5PMo10V2O40/UiO-66-NH2 for direct hydroxylation of benzene to phenol by H2O2.

To realize the direct hydroxylation of benzene to phenol by hydrogen peroxide, an efficient photoactive catalyst system was prepared by the recombination of H5PMo10V2O40 and UiO-66-NH2. The heterpolyacid was uniformly distributed on the UiO-66-NH2, and the combination was stable. The composite could effectively photocatalyze the direct hydroxylation of benzene to phenol by H2O2 in the mixture solution of acetonitrile and acetic acid. The yield and selectivity were 14.08% and 98.8% under the optimum condition, respectively. The performance of the catalyst still maintained well after 5 catalytic cycles. Hence, the investigated catalyst system might be applied in the field of hydroxylation of benzene to phenol.

Air‐Processed Organic Photovoltaics for Outdoor and Indoor Use Based upon a Tin Oxide‐Perylene Diimide Electron Transporting Bilayer

AbstractEfficient organic photovoltaics (OPV) based on SnO2 | perylene diimide (PDI) bilayer as an electron transport layer (ETL) is fabricated and tested in an ambient environment. The PTQ10:Y6 photoactive system is used as the primary bulk‐heterojunction. Without any surface treatment, the power conversion efficiency (PCE) of SnO2‐based OPV devices is 1.5%. Treating the SnO2 nano‐particles with UV‐ozone and then applying a layer of N‐annulated PDI with a functional NH bond (PDIN‐H) on top increase device PCEs to 9.2%. For indoor applications, the OPV device PCE rises from 8.1% to 12.3% when PDIN‐H is employed on SnO2 and tested under low light conditions, without the need for light soaking. The SnO2 | PDIN‐H ETL bilayer is slot‐die coated and corresponding OPV devices have a PCE of 7.9%, demonstrating utility for OPV scale‐up. The hybrid ETL is tested with other photoactive systems employing Y6, Y7, and IDIC as acceptors, as well as PM6 donor, and all these cases yield OPV devices with improved PCE when compared to OPV devices with SnO2‐only ETLs. These results show the successful implementation of SnO2 | PDIN‐H as an ETL for OPV.

Expanding Opportunities for Urea Electro-oxidation for Both Hydrogen Energy Storage and Cleaner Water

Oxidation of urea over nickel-catalysts is capable of such activity as to potentially disrupt several industrial and scientific fields, such as fuel cell power, and environmental pollution remediation. Though well suited for photoelectrochemical applications the reaction has commonly observed a loss in activity coinciding with the onset of oxygen evolution, leaving a narrow ~0.3 V electrochemical window. This narrow window limits many options for semiconductor substrates in a photoactive system. By adsorbing Ni-ions onto high surface area carbon black (CB) electrodes, instead of using metallic Ni catalysts, the loss in activity is avoided. The resulting oxidation window is expanded to over 1 V positive of urea’s oxidation onset potential. In addition to the expanded oxidation window, the use of a specially designed rotating-ring disc electrode is explored to electrochemically modify the local pH environment to limit the alkalinity of the bulk aqueous system. It is shown that with proper system parameters urea electro-oxidation is able to operate at 1 mA/cm2 despite the bulk solution’s neutral pH. This allows for a potentially additive-free use of this technology in environmental applications, or austere locations.

Thiol-end-functionalized Regioregular Poly(3-hexylthiophene) for PbS Quantum Dot Dispersions

Inorganic nanoparticles hybridized with π-conjugated polymers were successfully synthesized by the ligand exchange reaction of thiol-end-functionalized regioregular poly(3-hexylthiophene) (P3HT-SH) with lead sulfide (PbS) quantum dots (QDs). The hybrid material (P3HT-SH/PbS-QD) shows good dispersibility in organic solvents even after 6 months due to the decreased intermolecular interaction of PbS nanoparticles coated by highly soluble P3HT. The ultraviolet–visible–near infrared absorption spectra show a clear difference in PbS-QDs hybridized with oleic acid and P3HT-SH, depending on the size of the PbS-QDs. By using transmission electron microscopy, small clusters of PbS-QDs are observed at the nanolevel when hybridized with P3HT-SH, indicating the formation of nanoscale aggregates of PbS-QDs in the hybrid material. Preliminary results for fullerene-free photovoltaic applications showed that P3HT-SH/PbS-QD can deliver almost two times higher power conversion efficiency (PCE) than P3HT when paired with an n-type naphthalene-diimide-based semiconducting polymer (N2200) as the photoactive system. Such an increase in PCE can be attributed to the increased dielectric constant exerted by PbS-QDs, which facilitates charge dissociation. This study not only describes a method for synthesizing PbS-QD-based organic–inorganic hybrids but also reveals an interesting design direction for photovoltaic materials.

High-efficiency organic solar cells prepared using a halogen-free solution process

Although the power conversion efficiency (PCE) of organic photovoltaic (OPV) devices has recently improved to more than 16%, halogenated solution processes are typically employed to obtain optimal performance. However, halogenated processing is harmful to health and the environment, which can be a significant obstacle to commercialization. Therefore, development of active materials processable under halogen-free conditions is of great importance in this field. In this study, a 16.04% OPV device, processed under halogen-free conditions, is developed by employing a new active-blend system, PBDTTPD-HT:BTP-2F-BO. It is highly soluble in halogen-free solvents, forming a preferential bulk-heterojunction morphology. The PBDTTPD-HT:BTP-2F-BO device achieves a PCE comparable with current state-of-the-art devices based on PBDB-TF:BTP-4F (also known as PM6:Y6) using a conventional halogenated process (16.40% versus 16.33%). Furthermore, it demonstrates a significantly higher PCE than the PBDB-TF:BTP-4F device with a halogen-free process (16.04% versus 9.70%). • A halogen-free processable OPV device with a PCE of 16.04% is demonstrated • The device achieves a comparable PCE under halogenated and halogen-free processing conditions • The reported device with an active area of ∼1 cm 2 achieves a PCE of 14.93% • Preferential energy levels, solubility, and miscibility enhance performance of device In many cases, processing of organic photovoltaics uses conventional halogenated solvents, such as chloroform and chlorobenzene, which are significantly harmful to health and the environment. Wibowo et al. report a photoactive system that is processable under halogen-free conditions, showing that the active-blend system achieves similar performance under halogenated and halogen-free processing (16.40% versus 16.04%).

Carbon–titanium dioxide (C/TiO2) nanofiber composites for chemical oxidation of emerging organic contaminants in reactive filtration applications

Electrospun carbon nanofibers with integrated titanium dioxide nanoparticles are used for water treatment in a photoactive membrane filtration system.

Highly efficient inverted polymer solar cells by using solution processed MgO/ZnO composite interfacial layers

A highly efficient inverted polymer solar cell (PSC) has been successfully demonstrated by utilizing a wide bandgap magnesium oxide (MgO) film and ZnO stacked structure as an effective cathode interfacial layer. The MgO/ZnO bilayer structure is designed to combine the superiorities of both ZnO ETL and MgO film, based on the efficiency comparison of the PSCs without and with MgO interlayer. The ZnO film can serve as an efficient electron transport layer (ETL), while the MgO layer can reduce the surface defects of FTO and block the holes effectively, leading to an elevated electron collection and suppressed carrier recombination at the interface. With the excellent dual functions interface characteristics induced by the MgO/ZnO stacked films, the corresponding inverted PSC device based on the PTB7-Th:PC71BM photoactive layer system presents a superior power conversion efficiency (PCE) of 11.02%, which is higher than that of the PSC without MgO (8.79%). We believe that the MgO/ZnO bilayer structure is a superior interfacial contender for the organic photovoltaics and other photoelectric devices requiring cathode interfacial layers.