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To realize the practical application of energy conversion and storage devices for a sustainable future, improving their durability is critically important. The main problem with their durability is the chemical degradation of the active polymers used as material transport layers, photoactive layers, membranes, etc., for the device functions, mainly caused by detrimental radical species from unwanted side reactions. Introducing additives that scavenge radicals before their attack of the device‐configuring polymers is one of the promising strategies to significantly improve their life. In particular, Ce‐based radical scavengers including free Ce3+ are considered to be highly efficient radical scavengers, with a rapid and regenerative redox reaction. However, those radical scavengers possess detrimental interaction with the active materials in the devices, which hinders charge carrier and material transport for the device function, thereby reducing the device efficiency. Herein, an organometallic complex of Ce3+ is applied, and is coordinated by dipicolinate ligands as a radical scavenger for the chemical stability of polymers employed and durability enhancement in fuel cell and organic photovoltaic (OPV) device applications. Owing to the stabilizing effect of dipicolinate ligands toward Ce3+, disadvantageous interaction between radical scavenger and polymer material is suppressed, which results in the improved device stability without reducing the initial performance.

The performances of polymer solar cells (PSCs) based on non-fullerene acceptors (NFAs) have improved remarkably in recent years, but such devices are insufficiently stable for practical applications. Here, we investigated the effects of NFAs on PSC long-term stability. We found that high performance PBDBT : ITIC solar cells exhibit much lower stability than PTB7 : PC71BM devices in the 1 sunlight-soaking test; when compared with their initial performances, the performance of PTB7 : PCBM-based solar cells remains above 60% for over 4000 h, whereas that of PBDB-T : ITIC-based devices is reduced to one fifth after 1000 h. We demonstrated that the ITIC-based PSCs exhibit poor photo-stability because ITIC at the interface of the ZnO/active film is readily decomposed by a photocatalytic reaction; this poor stability arises because the vinyl group of ITIC is chemically more vulnerable than the stable aromatic units in the organic active materials. The decomposition of ITIC results in the degradation of the electron transport properties of the active materials located close to ZnO, which leads to severe burn-in degradation and reduced FF and VOC under illumination. It is thus highly important to develop intrinsically stable organic materials composed of chemically stable building blocks in order to realize stable and high efficiency PSCs. [ABSTRACT FROM AUTHOR]

The effects of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) doping on diketopyrrolo-pyrrole-based polymeric semiconductors in terms of charge transport behavior and structural ordering are systematically investigated. Although the energy level offset between the polymeric semiconductor and the F4TCNQ acceptor was not particularly large, ultraviolet photoelectron spectroscopy analyses revealed that a low doping ratio of 1 wt. % is sufficient to tune the energy distance between the Fermi level and the HOMO level, reaching saturation at roughly 5 wt. %, which is further confirmed by the depletion mode measurements of field effect transistors (FETs). Structural analyses using grazing-incidence X-ray diffraction (GIXD) show that the overall degree of edge-on orientation is disturbed by the addition of dopants, with significant influence appearing at high doping ratios (>3 wt. %). The calculated charge carrier mobility from accumulation mode measurements of FETs showed a maximum value of 2 cm²/V·s at the optimized doping ratio of 1%, enabled by additional holes in the channel region, which results in a roughly 40% increase relative to the undoped device. Further increases in the doping ratio, however, resulted in worse FET performance, which can be attributed to structural deformation. This result suggests that the electrochemical doping method can be also applied to donor-acceptor copolymers to further enhance their charge transport characteristics, once the optimized doping condition has been established. [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid tandem solar cells attract a considerable amount of attention due to their potential for realizing high efficiency photovoltaic devices at a low cost. Here, highly efficient triple-junction (TJ) hybrid tandem solar cells consisting of a double-junction (DJ) amorphous silicon (a-Si) cell and an organic photovoltaic (OPV) rear cell were developed. In order to design the TJ device in a logical manner, a simulation was carried out based on optical absorption and internal quantum efficiency. In the TJ architecture, the high-energy photons were utilized in a more efficient way than in the previously reported a-Si/OPV DJ devices, leading to a significant improvement in the overall efficiency by means of a voltage gain. The interface engineering such as tin-doped In2O3 deposition as an interlayer and its UV-ozone treatment resulted in the further improvement in the performance of the TJ solar cells. As a result, a power conversion efficiency of 7.81% was achieved with an open-circuit voltage of 2.35 V. The wavelength-resolved absorption profile provides deeper insight into the detailed optical response of the TJ hybrid solar cells. [ABSTRACT FROM AUTHOR]

Here we present synthesis and electronic properties of a new alternating copolymer composed of dithieno[2,3-d;2',3'-d']benzo[1,2-b;4,5-b']dithiophene (DTBDT) and diketopyrrolopyrrole units, poly dithienobenzodithiophene-co-diketopyrrolopyrrolebithiophene (PDPDBD). The resulting polymer showed hysteresis free, fast switching and highly reliable organic thin-film transistor properties comparable to a-Si. Hole mobility of the polymer is about 2.7 cm²V-1s-1, which is remarkably improved compared with its benzodithiophene (BDT)-analougue that contains a smaller aromatic ring of BDT in the place of DTBDT. This is mainly due to much increased intramolecular charge transport originated from PDPDBD's rigid molecular backbone. Furthermore, photoconductor devices fabricated by using PDPDBD as an active layer showed a high performance with the highest photoconductive gain of ~105. Taken together, the successful PDPDBD's transistor and photoconductor performances with high device stability demonstrated practical applicability of PDPDBD in low-cost and flexible optoelectronic devices. [ABSTRACT FROM AUTHOR]

Intense pulsed white light (IPWL) sintering was carried out at room temperature, which is suitable dye-sensitized solar cells (DSSCs) fabrication process on plastic substrates for the mass production. Five seconds irradiation of IPWL on TiO2 electrode significantly improves the photocurrent density and power conversion efficiency of DSSCs by more than 110% and 115%, respectively, compared to the DSSCs without IPWL treatment. These improvements were mainly attributed to the enhanced interconnection between the TiO2 nanoparticles induced by IPWL illumination, which is confirmed by the impedance spectra analysis. [ABSTRACT FROM AUTHOR]

Over the last ten years, polymer solar cells have been developed as an attractive alternative to the traditional silicon photovoltaic devices. Remarkable progress has been made in polymer-fullerene solar cells and several polymers have shown power conversion efficiencies (PCEs) greater than 7%. The most important recent development has been the synthesis of new low bandgap polymers with optimal properties for the solar cells. Herein we provide an overview of the key strategies of optimization of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels in the design of new low bandgap conjugated polymers. Detailed examples of representative donor polymers, the current state of the art in their solar cell performances and possible future directions for development of new polymers with improved efficiencies are discussed. [ABSTRACT FROM AUTHOR]

Herein, we describe the synthesis of fluorinated polythienothiophene-co-benzodithiophenes (PTBFs) and the characterization of their physical properties, especially their performance in solar cells. Fluorination of the polymer backbone lowered both the HOMO and LUMO energy levels and simultaneously widened the energy bandgap of the polymer (0.1-0.2 eV). Incorporation of fluorine into the various positions of the polymer backbone significantly affected the solar cells' power conversion efficiency from 2.3% to 7.2%. Detailed studies revealed that the polymer containing mono-fluorinated thienothiophene gave the best solar cell performance. Perfluorination of the polymer backbone led to poor compatibility with PC71BM molecules, thus poor solar energy conversion efficiency. This is possibly due to the enhanced self-organization properties of the polymer chains and the fluorophobicity effect. Furthermore, it was found that perfluorination of the polymer backbone resulted in poor photochemical stability against singlet oxygen attack. Theoretical studies indicated that the internal polarization caused enhancement of the negative charge density on thienothiophene rings, which rendered them vulnerable to [2+4] cycloaddition reaction with singlet oxygen. [ABSTRACT FROM AUTHOR]

Photocatalytic layers of amorphous TiO2 and polyvinyl alcohol were used for the patterning of low-resistivity metals such as copper and silver without using high cost materials and equipment. [ABSTRACT FROM AUTHOR]

The paper focuses on the description of a new low band gap semiconducting polymer for high performance polymer solar cells. The polymer, PTB 1 is synthesized by the Stille polycondensation between an ester substituted 2,5-dibromothieno[3,4-b]thiophene and dialkoxyl benzodithiophene distannane monomers. The solar cells prepared from the blend of this polymer and fullerene derivatives shows a high solar energy conversion efficiency of 5.6% and high fill factor of about 65%.