Vojislav I. Srdanov

Bio: Vojislav I. Srdanov is an academic researcher from University of California, Santa Barbara. The author has contributed to research in topics: Sodalite & Thin film. The author has an hindex of 25, co-authored 80 publications receiving 3252 citations.

Semiconducting polymer‐buckminsterfullerene heterojunctions: Diodes, photodiodes, and photovoltaic cells

Abstract: The characterization of rectifying heterojunctions (diodes) fabricated from a semiconducting polymer, a soluble derivative of poly(phenylene‐vinylene), and buckminsterfullerene, C60, are reported. Rectification ratios in the current versus voltage characteristics exceed 104. When illuminated, the devices exhibit a large photoresponse as a result of photoinduced electron transfer across the heterojunction interface from the semiconducting polymer (donor) onto C60 (acceptor). The photodiode and photovoltaic responses are characterized. Photoinduced electron transfer across the donor‐accepted rectifying heterojunction offers potential for photodetector and for solar cell applications.

Narrow Bandwidth Luminescence from Blends with Energy Transfer from Semiconducting Conjugated Polymers to Europium Complexes

Abstract: N. Ulman, S. G. Boxer, Science 1997, 275, 651. c) W. Knoll, Annu. Rev. Phys. Chem. 1998, 49, 569. [3] Crystallization of Nucleic Acids and Proteins: A Practical Approach (Eds: A. Ducruix, R. Giege), Oxford University Press, Oxford 1992. [4] S. D. Durbin, G. Feher, Annu. Rev. Phys. Chem. 1996, 47, 171. [5] O. D. Velev, E. W. Kaler, A. M. Lenhoff, unpublished. [6] See for example: a) D. E. Koppel, in Fast Methods in Physical Biochemistry and Cell Biology (Eds: R. I. Sha'afi, S. M. Fernandez), Elsevier, New York 1983, pp. 339±367. b) M. Edidin, in Mobility and Proximity in Biological Membranes (Eds: S. Damjanovich, J. SzoE llosi, L. Tron, M. Edidin), CRC Press, Boca Raton, FL 1994, pp. 109±135. [7] a) C. V. Kumar, A. Buranaprapuk, G. J. Opiteck, M. B. Moyer, S. Jockusch, N. J. Turro, Proc. Natl. Acad. Sci. USA 1998, 95, 10 361. b) C. V. Kumar, A. Buranaprapuk, J. Am. Chem Soc. 1999, 121, 4262. [8] J. R. Lakowicz, Principles of Fluorescence Spectroscopy, Plenum Press, New York 1983, pp. 341±381. [9] I. B. Berlman, Handbook of Fluorescence Spectra of Aromatic Molecules, Academic Press, New York 1971, pp. 383±385. [10] See for example: a) A. Ashkin, J. M. Dziedzic, J. E. Bjorkholm, S. Chu, Opt. Lett. 1986, 11, 288. b) S. Chu, Science 1991, 253, 861. c) D. G. Grier, Curr. Opin. Colloid Interface Sci. 1997, 2, 264. d) A. Ashkin, Proc. Natl. Acad. Sci. USA 1997, 94, 4853. [11] a) M. Ishikawa, H. Misawa, N. Kitamura, H. Masuhara, Chem. Lett. 1993, 481. b) J. Hotta, K. Sasaki, H. Masuhara, Y. Morishima, J. Phys. Chem. B 1998, 102, 7687. c) T. A. Smith, J. Hotta, K. Sasaki, H. Masuhara, Y. Itoh, J. Phys. Chem. B 1999, 103, 1660.

Synthesis of hydroazafullerene C59HN, the parent hydroheterofullerene

Abstract: THE electronic and geometric properties of C60 can be perturbed by replacing one or more carbon atoms of the fullerene skeleton with an atom of a different element. Exchange of one carbon atom with nitrogen, a trivalent atom with a lone pair of electrons, produces the azafullerene radical C59N, which is isoelectronic with the C60 radical anion. The process is slightly similar to doping silicon with phosphorus1. We have previously described the synthesis of the azafullerene dimer2; here we report the bulk preparation of the simplest azafullerene, C59HN. The electronic, vibrational and 13C NMR spectroscopic features of C59HN are similar to those of the dimer2, except for the signature of the sp3 (C–H) carbon. C59HN should open the door to a new chemistry of heterofullerenes.

Evidence for an Antiferromagnetic Transition in a Zeolite-Supported Cubic Lattice of F Centers

Abstract: Evidence for a bcc lattice of $F$ centers in sodium-electro-sodalite (SES), synthesized by exposing dehydrated sodalite to sodium vapor, is presented. A high electron spin density in SES produces isotropic contact shifts in nuclear magnetic resonance (NMR) spectra of the framework nuclei whose magnitude is a discrete function of local electron density. Strong exchange coupling between unpaired electrons gives rise to an antiferromagnetic phase transition in SES at ${T}_{N}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}48\ifmmode\pm\else\textpm\fi{}2\mathrm{K}$, providing the first example of an $s\ensuremath{-}\mathrm{electron}$ antiferromagnet.

Polymer photovoltaic cells : enhanced efficiencies via a network of internal donor-acceptor heterojunctions

Abstract: The carrier collection efficiency (ηc) and energy conversion efficiency (ηe) of polymer photovoltaic cells were improved by blending of the semiconducting polymer with C60 or its functionalized derivatives. Composite films of poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) and fullerenes exhibit ηc of about 29 percent of electrons per photon and ηe of about 2.9 percent, efficiencies that are better by more than two orders of magnitude than those that have been achieved with devices made with pure MEH-PPV. The efficient charge separation results from photoinduced electron transfer from the MEH-PPV (as donor) to C60 (as acceptor); the high collection efficiency results from a bicontinuous network of internal donor-acceptor heterojunctions.

Conjugated polymer-based organic solar cells

Abstract: The need to develop inexpensive renewable energy sources stimulates scientific research for efficient, low-cost photovoltaic devices.1 The organic, polymer-based photovoltaic elements have introduced at least the potential of obtaining cheap and easy methods to produce energy from light.2 The possibility of chemically manipulating the material properties of polymers (plastics) combined with a variety of easy and cheap processing techniques has made polymer-based materials present in almost every aspect of modern society.3 Organic semiconductors have several advantages: (a) lowcost synthesis, and (b) easy manufacture of thin film devices by vacuum evaporation/sublimation or solution cast or printing technologies. Furthermore, organic semiconductor thin films may show high absorption coefficients4 exceeding 105 cm-1, which makes them good chromophores for optoelectronic applications. The electronic band gap of organic semiconductors can be engineered by chemical synthesis for simple color changing of light emitting diodes (LEDs).5 Charge carrier mobilities as high as 10 cm2/V‚s6 made them competitive with amorphous silicon.7 This review is organized as follows. In the first part, we will give a general introduction to the materials, production techniques, working principles, critical parameters, and stability of the organic solar cells. In the second part, we will focus on conjugated polymer/fullerene bulk heterojunction solar cells, mainly on polyphenylenevinylene (PPV) derivatives/(1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C61) (PCBM) fullerene derivatives and poly(3-hexylthiophene) (P3HT)/PCBM systems. In the third part, we will discuss the alternative approaches such as polymer/polymer solar cells and organic/inorganic hybrid solar cells. In the fourth part, we will suggest possible routes for further improvements and finish with some conclusions. The different papers mentioned in the text have been chosen for didactical purposes and cannot reflect the chronology of the research field nor have a claim of completeness. The further interested reader is referred to the vast amount of quality papers published in this field during the past decade.

A grid-based Bader analysis algorithm without lattice bias

Abstract: A computational method for partitioning a charge density grid into Bader volumes is presented which is efficient, robust, and scales linearly with the number of grid points. The partitioning algorithm follows the steepest ascent paths along the charge density gradient from grid point to grid point until a charge density maximum is reached. In this paper, we describe how accurate off-lattice ascent paths can be represented with respect to the grid points. This improvement maintains the efficient linear scaling of an earlier version of the algorithm, and eliminates a tendency for the Bader surfaces to be aligned along the grid directions. As the algorithm assigns grid points to charge density maxima, subsequent paths are terminated when they reach previously assigned grid points. It is this grid-based approach which gives the algorithm its efficiency, and allows for the analysis of the large grids generated from plane-wave-based density functional theory calculations.

Semiconducting tin and lead iodide perovskites with organic cations: phase transitions, high mobilities, and near-infrared photoluminescent properties.

Abstract: A broad organic–inorganic series of hybrid metal iodide perovskites with the general formulation AMI3, where A is the methylammonium (CH3NH3+) or formamidinium (HC(NH2)2+) cation and M is Sn (1 and 2) or Pb (3 and 4) are reported. The compounds have been prepared through a variety of synthetic approaches, and the nature of the resulting materials is discussed in terms of their thermal stability and optical and electronic properties. We find that the chemical and physical properties of these materials strongly depend on the preparation method. Single crystal X-ray diffraction analysis of 1–4 classifies the compounds in the perovskite structural family. Structural phase transitions were observed and investigated by temperature-dependent single crystal X-ray diffraction in the 100–400 K range. The charge transport properties of the materials are discussed in conjunction with diffuse reflectance studies in the mid-IR region that display characteristic absorption features. Temperature-dependent studies show a ...