Materials For Photovoltaic Devices Research Articles

Carbon nanotubes as integrative materials for organic photovoltaic devices

In this Highlight article we conduct a critical evaluation of recent advances in the use of carbon nanotubes (CNT) for photocurrent generation. In particular, two strategies have been described. On one hand, CNT serve as photoactive material in photovoltaic devices. Alternatively, CNT are implemented as semitransparent conducting material in the construction of electrodes. Hereby, the following incentives are considered: flexible, transparent, more efficient, and large area organic photovoltaic devices.

High Efficiency Organic Photovoltaics Incorporating a New Family of Soluble Fullerene Derivatives

A novel class of soluble fullerenoids based on a dihydronaphthyl functionalization have been synthesized and characterized. Initial testing of these materials in photovoltaic devices identifies a new soluble fullerene derivative, which when blended with poly(3-hexylthiophene) is capable of 4.5% power conversion efficiencies under standard illumination conditions.

Linear π‐Conjugated Systems Derivatized with C60‐Fullerene as Molecular Heterojunctions for Organic Photovoltaics

AbstractFor Abstract see ChemInform Abstract in Full Text.

Linear π-conjugated systems derivatized with C60-fullerene as molecular heterojunctions for organic photovoltaics

This tutorial review covers recent contributions in the area of linear pi-conjugated systems bound to fullerenes in view of their application as active materials in photovoltaic devices. The first part discusses the concepts of double-cable polymer and molecular hetero-junction and presents several examples of chemically or electrochemically synthesized C60-derivatized conjugated polymers. The second and main part of the article concerns the various classes of C60-derivatized pi-conjugated oligomers designed in view of their utilization in single-component photovoltaic devices. Thus, C60-containing pi-conjugated systems such as oligoarylenevinylenes, oligoaryleneethynylenes and oligothiophenes are discussed on the basis of the relationships between molecular structure, photophysical properties and performances of the derived photovoltaic devices. A brief last section presents some recent examples of surface-attached molecular hetero-junctions based on self-assembled monolayers and discusses possible routes for future research.

A New Iterative Approach for the Synthesis of Oligo(phenyleneethynediyl) Derivatives and Its Application for the Preparation of FullereneOligo(phenyleneethynediyl) Conjugates as Active Photovoltaic Materials

AbstractDisymmetrically substituted oligo(phenyleneethynediyl) (OPE) derivatives were prepared from 2,5‐bis(octyloxy)‐4‐[(triisopropylsilyl)ethynyl]benzaldehyde (5) by an iterative approach using the following reaction sequence: i) Corey–Fuchs dibromoolefination, ii) treatment with an excess of lithium diisopropylamide, and iii) a metal‐catalyzed cross‐coupling reaction of the resulting terminal alkyne with 2,5‐diiodo‐1,4‐bis(octyloxy)benzene (3) (Schemes 2 and 3). Reaction of the OPE dimer 8 and trimer 13 thus obtained with N‐methylglycine and C60 in refluxing toluene gave the corresponding C60OPE conjugates 16 and 17, respectively (Scheme 4). On the other hand, treatment of the protected terminal alkynes 8 and 13 with Bu4N followed by reaction of the resulting 9 and 14 with 4‐iodo‐N,N‐dibutylaniline under Sonogashira conditions yielded 10 and 15, respectively (Schemes 2 and 3). Subsequent treatment with N‐methylglycine and C60 in refluxing toluene furnished the C60OPE derivatives 18 and 19 (Scheme 4). Compound 9 was also subjected to a Pd‐catalyzed cross‐coupling reaction with 3 to give the centrosymmetrical OPE pentamer 20 (Scheme 5). Subsequent reduction followed by reaction of the resulting diol 21 with acid 22 under esterification conditions led to bis‐malonate 23. Oxidative coupling of terminal alkyne 14 with the Hay catalyst gave bis‐aldehyde 24 (Scheme 6). Treatment with diisobutylaluminium hydride followed by dicylcohexylcarbodiimide‐mediated esterification with acid 22 gave bis‐malonate 26. Finally, treatment of bis‐malonates 23 and 26 with C60, I2, and 1,8‐diazabicylco[5.4.0]undec‐7‐ene (DBU) in toluene afforded the bis[cyclopropafullerenes] 27 and 28, respectively (Scheme 7). The C60 derivatives 16–19, 27, and 28 were tested as active materials in photovoltaic devices. Each C60OPE conjugate was sandwiched between poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate)‐covered indium tin oxide and aluminium electrodes. Interestingly, the performances of the devices prepared from the N,N‐dialkylaniline‐terminated derivatives 18 and 19 are significantly improved when compared to those obtained with 16, 17, 27, and 28, thus showing that the efficiency of the devices can be significantly improved by increasing the donor ability of the OPE moiety.

Photophysics and photovoltaic device properties of phthalocyanine–fullerene dyad:conjugated polymer mixtures

The phthalocyanine–fullerene dyad Pc-C60 is an intramolecular donor–acceptor system that can be used as photoactive material in photovoltaic devices. The photocurrent shows maxima below 400 and 700 nm, but only a small response in the range around 500 nm. To improve the spectral match to the solar emission spectrum, an energy transfer process from the conjugated polymer poly [2-methoxy-5-(3′,7′-dimethyloctyloxy)-1-4-phenylene vinylene] MDMO-PPV (antenna system) to the dyad compound can be used. The photophysics of the energy transfer process was studied with luminescence measurements and sub-picosecond time-resolved transmission changes. The influence of the polymeric antenna system on the photovoltaic device properties was measured with spectrally resolved photocurrent (IPCE) measurements. Photocurrent in nearly the full visible spectral range was obtained. In addition, Pc-C60 was also added as third component to MDMO-PPV:PCBM mixtures. The photocurrent around 700 nm was increased, however with reduction in the short-circuit current under white light illumination.

Star-shaped heptamers of discotic dyes as new materials for photovoltaic devices

AbstractPotentially n-type and p-type semi-conducting discotic liquid crystal dyes are linked together to star-shaped heptamers, which might self-organize into super-columns of separated p-type and n-type columnar stacks. Their synthesis, mesomorphism, and electronic properties will be discussed along with their potential use in photovoltaic devices.

Studies of virtually insoluble systems with large interfacial area: CdTe–ZnO

Abstract Exchange of matter at CdTe/ZnO heterojunctions was studied in (a) polycrystalline CdTe with dispersed ZnO and (b) single crystals of CdTe in contact with compressed ZnO powders. Scanning electron microscopy with electron microprobe analysis, differential thermal analysis and X-ray diffraction were the experimental techniques utilized to investigate CdTe–ZnO. Samples (a) were heated to 950°C or 1110°C and (b) to 950°C, for 60 min. Zn x Cd (1− x ) Te formed at CdTe/ZnO interfaces by thermal treatment. The magnitude of the diffusion of Zn in CdTe was estimated and found in agreement with earlier studies. A superlattice, attributable to ordering of zinc in CdTe, was suggested by preliminary single crystal XRD data from Zn x Cd (1− x ) Te microcrystals. Diffusion of zinc was faster in single crystals than in polycrystals. The study of CdTe with dispersed ZnO complements a series of studies on dispersed second phase materials. The work was carried out over the last 30 years at Professor J.B. Wagner's research laboratories, with the following outcome: Transport depended on surface area of the dispersed phase and of the matrix. Changes in electrical and mass transport, and in phase transformation temperatures, due to the presence of dispersoids, were consistent with an interpretation by the space charge model. The present results on the chemistry and microstructure CdTe with dispersed ZnO, in conjunction with the knowledge accrued on transport in dispersed second phase systems, indicate a potential application of this material in photovoltaic devices.

Photoinduced processes in fullerenopyrrolidine and fullerenopyrazoline derivatives substituted with an oligophenylenevinylene moietyElectronic supplementary information (ESI) available: synthetic procedures and full characterization of all new compounds. See http://www.rsc.org/suppdata/jm/b2/b200432a/

Fullerene derivatives A-3PV and B-3PV in which an oligophenylenevinylene trimeric subunit (3PV) is attached to C60 through, respectively, a pyrrolidine or a pyrazoline ring have been prepared. The electrochemical and excited-state properties of the multicomponent arrays A-3PV and B-3PV have been investigated in solution using the related oligophenylenevinylene derivative 3PV, fullerenopyrrolidine A and fullerenopyrazoline B as reference compounds. In A-3PV quantitative OPV → C60 photoinduced singlet–singlet energy transfer has been observed. Population of the lowest fullerene singlet excited state is followed by nearly quantitative intersystem crossing to the lowest fullerene triplet excited state in CH2Cl2 and toluene, whereas OPV → C60 electron transfer is able to compete significantly in the more polar solvent benzonitrile. In the case of B-3PV, the excited-state properties are more complex due to the electron donating ability of the pyrazoline ring. As observed for A-3PV, quantitative OPV → C60 photoinduced singlet–singlet energy transfer occurs in B-3PV. However, in this case, the population of the lowest fullerene singlet excited state is followed by an efficient electron transfer from the pyrazoline ring in CH2Cl2 and benzonitrile. In B-3PV, studies of the dependence of photoinduced processes on solvent polarity, addition of acid, and temperature also reveal that this compound can be considered as a fullerene-based molecular switch, the switchable parameters being the photoinduced processes. Finally, A-3PV and B-3PV have been tested as active materials in photovoltaic devices and the differences of light to energy conversion efficiencies found for the two compounds have been rationalised on the basis of their photophysical properties.

CuxSbySz THIN FILMS PRODUCED BY ANNEALING CHEMICALLY DEPOSITED Sb2S3-CuS THIN FILMS

The possibility of generating ternary compounds through annealing thin film stacks of binary composition has been demonstrated before. In this work we report a method to produce large area coating of ternary compounds through a reaction in solid state between thin films of Sb2S3 and CuS. Thin films of Sb2S3 -CuS were deposited on glass substrates in the sequence of Sb2S3 followed by CuS (on Sb2S3 ) using chemical bath deposition method. The multilayer stack, thus produced, of approximately 0.5 μm in thickness, where annealed under nitrogen and argon atmospheres at different temperatures to produce films of ternary composition, CuxSbySz . An optical band gap of ~1.5 eV was observed in these films, suggesting that the thin films of ternary composition formed in this way are suitable for use as absorber materials in photovoltaic devices. The results on the analyses of structural, electrical and optical properties of films formed with different combinations of thickness in the multilayers will be discussed in the paper.

Materials for Photovoltaics

Despite the fact that the 1980s have been a period in which public and government support for photovoltaics has been greatly underemphasized, it is heartening to realize that considerable activity in research and development of solar cells continues, as does a steady, positive experience in the field. In order to focus on the most recent developments in the utilization of materials in photovoltaic devices, this paper is limited primarily to publications from 1987 through 1989. The development of materials for photovoltaic energy conversion is a significant contribution to the development of alternative energy sources. Students of the energy question have realized for some time that traditional sources of energy (coal, oil, natural gas) supply only a limited reservoir when future energy needs of the earth are considered in terms of hundreds rather than tens of years. Recently, we have become increasingly aware of other problems associated with energy production by the combustion of fossil fuels as well: air pollution, acid rain, and the greenhouse effect, to mention only a few. In particular, the greenhouse effect is raising an increasing concern. This paper discusses the materials used for photovoltaics.

Studies of Organic Semiconductors for 40 Years—VIII

Abstract Research in organic semiconductors started in China during the wake of press release of pyrolyzed polyacrylonitrile (PAN) as a semiconductor by the Academy of Sciences, U.S.S.R. in 1958. Big interest was aroused at that time in various research institutions throughout China, particularly Changchun Institute of Applied Chemistry, Institute of Physics and Institute of Chemistry, all of Academia Sinica. This wave of studies slacked up gradually and was virtually stopped in mid-sixties. Then research in this field resumed in early seventies, oriented toward the search for organic photoconductors, and materials for photovoltaic devices and electrophotography. In August 1978 Professor Martin Pope of New York University gave a series of lectures in Institute of Chemistry, Academia Sinica, Beijing, on the electronic processes in organic solids. The lecture notes supplemented with more recent developments in organic metallic conductors have been published.1 Some fifty researchers participated in this work...