Vladimir A. Dyakov

Novel indolin-2-one-substituted methanofullerenes bearing long n-alkyl chains: synthesis and application in bulk-heterojunction solar cells

Summary An easy, high-yield and atom-economic procedure of a C60 fullerene modification using a reaction of fullerene C60 with N-alkylisatins in the presence of tris(diethylamino)phosphine to form novel long-chain alkylindolinone-substituted methanofullerenes (AIMs) is described. Optical absorption, electrochemical properties and solubility of AIMs were studied. Poly(3-hexylthiophene-2,5-diyl) (P3HT)/AIMs solar cells were fabricated and the effect of the AIM alkyl chain length and the P3HT:AIM ratio on the solar cell performance was studied. The power conversion efficiencies of about 2% were measured in the P3HT/AIM devices with 1:0.4 P3HT:AIM weight ratio for the AIMs with hexadecyl and dodecyl substituents. From the optical and AFM data, we suggested that the AIMs, in contrast to [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), do not disturb the P3HT crystalline domains. Moreover, the more soluble AIMs do not show a better miscibility with the P3HT crystalline phase.

Parametric generation of high-peak-power femtosecond light pulses in LBO crystal

The parametric down conversion of femtosecond pulses at high intensity is discussed. An injection-locked parametric oscillator based on a nonlinear LBO crystal pumped by XeCl- and dye-laser systems is developed. The nonlinear refractive index n2 approximately equals 1.7 10-16 cm2/W and the optical surface breakdown threshold Ibr approximately equals 3.8 1013 W/cm2 of LBO crystal for approximately 400 fsec pulses were measured. The spatial dispersion of effective nonlinearity deff2/n3 for parametric amplification in LBO crystal is calculated. The design and performance of femtosecond dye- laser system and XeCl-excimer-laser system capable of producing a focused intensity in excess of 1016 W/cm2 are described.

New ferroelastic: LiNaCO3

Abstract New ferroelastic LiNaCO3 was grown as a single crystal. First observations of α-β-transition in the crystal, corresponding domain pattern, and some physical properties were performed, which are consistent with the ferroelastic nature of α-phase.

Low-operation-voltage electro-optical modulator based on Fe:KNbO3 crystal

Results of low- and high-frequency modulation of laser beam, propagating both in the direction of optical axis and along three crystallographic axes in Fe-doped KNb03 crystal, are presented. It was found, that the high-frequency electro-optical constants of Fe:KNb03 are: r33 = (5353) pm/V, r13 = (21±3) pm/V, and r51 = (88±11) p d V . The difference between high- and low-frequency values is about 20% and this is in good accordance with known data for nominally pure crystal. We found also, that there was no twinning effect in this crystal under the electrical fields up to 2.5 kV/cm. The half-wave voltage was only 800 V at the wavelength of 633 nm in a longitudinal configuration of modulator. We measure also that bandpass of light modulation in Fe:KNb03 is equal to at least 6 MHz. In our experiments we also determined the speed of acoustic waves, created in the crystal by inverse piezoelectric effect, when fast HV electrical pulse is applied to it, these values are vl=(56001100) d s and v2=(6400±100) m/s along Oz and Ox axes correspondingly.

Fast growth of acid KDP crystals and their optical quality

The influence of acidity of KDP salt solution on KDP crystal properties has been investigated. A number of crystals were grown from acid solutions in wide range of solution acidity. Optical properties of the crystals were studied. It has been found that UV absorption of KDP crystals depends on the acidity of solution.