Facile Synthesis of Novel Conducting Copolymers Based on N-Furfuryl Pyrrole and 3,4-Ethylenedioxythiophene with Enhanced Optoelectrochemical Performances Towards Electrochromic Application.

In this article, a series of novel conducting copolymers P(FuPy--EDOT) are prepared via cyclic voltammetry electropolymerization method by using N-furfuryl pyrrole (FuPy) and 3,4-ethylenedioxythiophene (EDOT) as comonomers. The molecular structure, surface morphology, electrochemical, and optical properties of the resulting copolymers are characterized in detail upon varying the feed ratios of FuPy/EDOT in the range of 1/1 to 1/9. The results demonstrate that the prepared P(FuPy--EDOT) copolymers with a higher proportion of EDOT units (FuPy/EDOT: 2/8~1/9) possess good redox activity, tunable optical absorption performances, and low band gaps (1.

Manipulating Intramolecular Charge Transfer in Terpyridine Derivatives Towards "Turn-On" Fluorescence Chemosensors for Zn.

A series of donor-acceptor (D-A) terpyridine derivatives with various intramolecular charge transfer interactions have been successfully synthesized bearing phenyl, methoxyphenyl, N-butyldiphenylamine (DPA), and triphenylamine (TPA) as electron-donors and terpyridine (TPY), 2,6-di(pyrazin-2-yl)pyridine (PYDPZ), and N,N-dimethylated PYDPZ (PYDPZ-2CH) as electron acceptors. Upon the introduction of pyrazine rings instead of pyridine ones and further selective N,N'-dimethylation, the intramolecular D-A interactions are significantly enhanced, resulting in the remarkable reduced intramolecular charge transfer (ICT) transitions and quenched PL emissions in CHCl solution. However, their ICT emissions are clearly recovered upon adding Zn.

Multifunctional Effects of Biguanide Derivative in the Application of Highly Efficient Tin-Lead Perovskite Solar Cells.

Tin-lead (Sn-Pb) mixed perovskites is beneficial to a single-junction or all-perovskite tandem device. However, the poor quality of the perovskite surface resulting from Sn oxidation and uncontrollable crystallization degrades device performance and stability. Herein, based on interface engineering, a novel biguanide derivative of PZBGACl is employed that integrates different types of N-related groups to reconstruct the surface/grain boundaries of Sn-Pb perovskite.

A Newly Crosslinked-double Network PEDOT:PSS@PEGDMA toward Highly-Efficient and Stable Tin-Lead Perovskite Solar Cells.

Until now, poly(3,4-ethylenedioxythiophene):poly(styrensulfonate) (PEDOT:PSS) is widely used in Sn-Pb perovskite solar cells (PSCs) due to its many advantages, including high optical transparency, suitable conductivity, superior wettability, and so on. However, the acidic and hydroscopic properties of the PSS component, as well as the incongruous energy level of the hole transport layer (HTL), may lead to unsatisfying interface properties and decreased device performance. Herein, by adding polyethylene glycol dimethacrylate (PEGDMA) into PEDOT:PSS, a newly crosslinked-double-network obtain of PEDOT:PSS@PEGDMA film, which could not only optimize nucleation and crystallinity of Sn-Pb perovskite films, but also suppress defect density and optimize energy level alignment at the HTL/perovskite interface.

Multifunctional Ionic Liquid as an Interfacial Modifier for High-Performance and Stable NiO-Based Inverted Perovskite Solar Cells.

Interface instability has evolved into the primary aspect that limits the durability improvement of perovskite solar cells (PSCs). Interface modification with suitable molecules is widely considered an effective path for improving the interface state. Herein, an ionic liquid modified layer, 1-ethyl-3-methylimidazolium aminoacetate (EMIMAE), is brought to modify NiO/perovskite interface.

In Situ Perovskitoid Engineering at SnO Interface toward Highly Efficient and Stable Formamidinium Lead Triiodide Perovskite Solar Cells.

The black-phase formamidinium lead triiodide (α-FAPbI) perovskite has turned out to be one of the most efficient light harvesting materials. However, the phase stability of FAPbI is a long-standing issue. Herein, we introduce a layer of tetrabutylammonium fluoride (TBAF) on SnO, which would form an in situ layer of TBAPbI perovskitoid at the SnO/FAPbI interface by interacting with PbI.

Stable Layered 2D Perovskite Solar Cells with an Efficiency of over 19% via Multifunctional Interfacial Engineering.

Layered 2D perovskites have been extensively investigated by scientists with photovoltaics (PV) expertise due to their good environmental stability. However, a random phase distribution in the perovskite film could affect both the performance and stability of the devices. To overcome this problem, we propose multifunctional interface engineering of 2D GAMAPbI perovskite by employing guanidinium bromide (GABr) on top of it to optimize the secondary crystallization process.

Multifunctional molecular modulators for perovskite solar cells with over 20% efficiency and high operational stability.

Perovskite solar cells present one of the most prominent photovoltaic technologies, yet their stability, scalability, and engineering at the molecular level remain challenging. We demonstrate a concept of multifunctional molecular modulation of scalable and operationally stable perovskite solar cells that exhibit exceptional solar-to-electric power conversion efficiencies. The judiciously designed bifunctional molecular modulator SN links the mercapto-tetrazolium (S) and phenylammonium (N) moieties, which passivate the surface defects, while displaying a structure-directing function through interaction with the perovskite that induces the formation of large grain crystals of high electronic quality of the most thermally stable formamidinium cesium mixed lead iodide perovskite formulation.

Formation of Stable Mixed Guanidinium-Methylammonium Phases with Exceptionally Long Carrier Lifetimes for High-Efficiency Lead Iodide-Based Perovskite Photovoltaics.

Methylammonium (MA)- and formamidinium (FA)-based organic-inorganic lead halide perovskites provide outstanding performance as photovoltaic materials, due to their versatility of fabrication and their power conversion efficiencies reaching over 22%. The proposition of guanidinium (GUA)-doped perovskite materials generated considerable interest due to their potential to increase carrier lifetimes and open-circuit voltages as compared to pure MAPbI. However, simple size considerations based on the Goldschmidt tolerance factor suggest that guanidinium is too big to completely replace methylammonium as an A cation in the APbI perovskite lattice, and its effect was thus ascribed to passivation of surface trap states at grain boundaries.

Isomer-Pure Bis-PCBM-Assisted Crystal Engineering of Perovskite Solar Cells Showing Excellent Efficiency and Stability.

A fullerene derivative (α-bis-PCBM) is purified from an as-produced bis-phenyl-C -butyric acid methyl ester (bis-[60]PCBM) isomer mixture by preparative peak-recycling, high-performance liquid chromatography, and is employed as a templating agent for solution processing of metal halide perovskite films via an antisolvent method. The resulting α-bis-PCBM-containing perovskite solar cells achieve better stability, efficiency, and reproducibility when compared with analogous cells containing PCBM. α-bis-PCBM fills the vacancies and grain boundaries of the perovskite film, enhancing the crystallization of perovskites and addressing the issue of slow electron extraction.

Morphology Engineering: A Route to Highly Reproducible and High Efficiency Perovskite Solar Cells.

Despite the rapid increase in the performance of perovskite solar cells (PSC), they still suffer from low lab-to-lab or people-to-people reproducibility. Aiming for a universal condition to high-performance devices, we investigated the morphology evolution of a composite perovskite by tuning annealing temperature and precursor concentration of the perovskite film. Here, we introduce thermal annealing as a powerful tool to generate a well-controlled excess of PbI in the perovskite formulation and show that this benefits the photovoltaic performance.

Dopant-Free Donor (D)-π-D-π-D Conjugated Hole-Transport Materials for Efficient and Stable Perovskite Solar Cells.

Three novel hole-transporting materials (HTMs) using the 4-methoxytriphenylamine (MeOTPA) core were designed and synthesized. The energy levels of the HTMs were tuned to match the perovskite energy levels by introducing symmetrical electron-donating groups linked with olefinic bonds as the π bridge. The methylammonium lead triiodide (MAPbI ) perovskite solar cells based on the new HTM Z34 (see main text for structure) exhibited a remarkable overall power conversion efficiency (PCE) of 16.

A vacuum flash-assisted solution process for high-efficiency large-area perovskite solar cells.

Metal halide perovskite solar cells (PSCs) currently attract enormous research interest because of their high solar-to-electric power conversion efficiency (PCE) and low fabrication costs, but their practical development is hampered by difficulties in achieving high performance with large-size devices. We devised a simple vacuum flash-assisted solution processing method to obtain shiny, smooth, crystalline perovskite films of high electronic quality over large areas. This enabled us to fabricate solar cells with an aperture area exceeding 1 square centimeter, a maximum efficiency of 20.

High-Performance Perovskite Solar Cells with Enhanced Environmental Stability Based on Amphiphile-Modified CH3 NH3 PbI3.

A new aliphatic fluorinated amphiphilic additive is added to CH3 NH3 PbI3 perovskite to tune the morphology and enhance the environmental stability without sacrificing the performance of the devices. Judicious screening of the perovskite precursor solution realizes a power conversion efficiency of 18.0% for mesoporous perovskite solar cells as a result of improved surface coverage.

High-Efficiency Perovskite Solar Cells Employing a S,N-Heteropentacene-based D-A Hole-Transport Material.

We developed a new donor-π-acceptor-type hole-transport material (HTMs) incorporating S,N-heteropentacene as π-spacer, triarylamine as donor, and dicyanovinylene as acceptor. In addition to appropriate frontier molecular orbital energies, the new HTM showed high photo absorptivity in the visible region. Without the use of p-dopants, solution-processed mixed perovskite devices using the HTM achieved power conversion efficiencies of up to 16.

Efficient luminescent solar cells based on tailored mixed-cation perovskites.

We report on a new metal halide perovskite photovoltaic cell that exhibits both very high solar-to-electric power-conversion efficiency and intense electroluminescence. We produce the perovskite films in a single step from a solution containing a mixture of FAI, PbI2, MABr, and PbBr2 (where FA stands for formamidinium cations and MA stands for methylammonium cations). Using mesoporous TiO2 and Spiro-OMeTAD as electron- and hole-specific contacts, respectively, we fabricate perovskite solar cells that achieve a maximum power-conversion efficiency of 20.

Improved morphology control using a modified two-step method for efficient perovskite solar cells.

A two-step wet chemical synthesis method for methylammonium lead(II) triiodide (CH3NH3PbI3) perovskite is further developed for the preparation of highly reproducible solar cells, with the following structure: fluorine-doped tin oxide (FTO)/TiO2 (compact)/TiO2 (mesoporous)/CH3NH3PbI3/spiro-OMeTAD/Ag. The morphology of the perovskite layer could be controlled by careful variation of the processing conditions. Specifically, by modifying the drying process and inclusion of a dichloromethane treatment, more uniform films could be prepared, with longer emission lifetime in the perovskite material and longer electron lifetime in solar cell devices, as well as faster electron transport and enhanced charge collection at the selective contacts.

Electronic Structure of TiO2/CH3NH3PbI3 Perovskite Solar Cell Interfaces.

The electronic structure and chemical composition of efficient CH3NH3PbI3 perovskite solar cell materials deposited onto mesoporous TiO2 were studied using photoelectron spectroscopy with hard X-rays. With this technique, it is possible to directly measure the occupied energy levels of the perovskite as well as the TiO2 buried beneath and thereby determine the energy level matching of the interface. The measurements of the valence levels were in good agreement with simulated density of states, and the investigation gives information on the character of the valence levels.

Efficient and stable CH3NH3PbI3-sensitized ZnO nanorod array solid-state solar cells.

We report for the first time the use of a perovskite (CH3NH3PbI3) absorber in combination with ZnO nanorod arrays (NRAs) for solar cell applications. The perovskite material has a higher absorption coefficient than molecular dye sensitizers, gives better solar cell stability, and is therefore more suited as a sensitizer for ZnO NRAs. A solar cell efficiency of 5.

Effect of Different Hole Transport Materials on Recombination in CH3NH3PbI3 Perovskite-Sensitized Mesoscopic Solar Cells.

We report on perovskite (CH3NH3)PbI3-sensitized solid-state solar cells using spiro-OMeTAD, poly(3-hexylthiophene-2,5-diyl) (P3HT) and 4-(diethylamino)benzaldehyde diphenylhydrazone (DEH) as hole transport materials (HTMs) with a light to electricity power conversion efficiency of 8.5%, 4.5%, and 1.

Initial light soaking treatment enables hole transport material to outperform spiro-OMeTAD in solid-state dye-sensitized solar cells.

Efficient solid state dye-sensitized solar cells (sDSCs) were obtained using a small hole transport material, MeO-TPD (N,N,N',N'-tetrakis(4-methoxyphenyl)benzidine), after an initial light soaking treatment. It was discovered that the light soaking treatment for the MeO-TPD based solar cells is essential in order to achieve the high efficiency (4.9%), which outperforms spiro-OMeTAD based sDSCs using the same dye and device preparation parameters.

Iodine-sensitized degradation of 2,4,6-trichlorophenol under visible light.

Molecular iodine has been studied, for the first time, as a sensitizer for the degradation of 2,4,6-trichlorophenol (TCP) in aqueous solution under visible light (λ ≥ 450 nm). TCP was degraded in the presence of commercial I(2), but the reaction rate decreased significantly after 2 h. When a solution of NaI and H(2)O(2) was used as an iodine source with phosphotungstic acid (PW) as a catalyst, TCP degradation was not only fast but also followed zero-order kinetics.

Improved photocatalytic activity of WO3 through clustered Fe2O3 for organic degradation in the presence of H2O2.

Photocatalytic degradation of organic substrates over WO(3) in an aerated aqueous suspension is very slow due to the difficulty of O(2) reduction by the conduction band electron on WO(3). In this work, we report on H(2)O(2) as an electron scavenger significantly accelerating the photodegradation of phenol and azo-dye X3B in water under UV or visible light. More importantly, an iron-containing WO(3) (FeW) synthesized through thermal decomposition of a ferrotungstenic acid displayed a much higher activity than pure WO(3) (HW) prepared in parallel.