In this paper, we present results from the detailed investigations on the synthesis, optical, emission, electrochemical, and ultrafast nonlinear optical (NLO) properties along with the excited state dynamics of zinc­(II) 2,10,16,24-tetrakis­(9-phenyl-9H-carbazol-2-yl)­phthalocyanine (CBZPC1) and zinc­(II) 2,10,16,24-tetrakis­(4-(9H-carbazol-9-yl)­phenyl)­phthalocyanine (CBZPC2). Due to the presence of carbazole moieties, the Soret band was found to be broadened. The emission studies performed using different solvents revealed the fluorescence yields in the range of 0.10–0.27 and the time-resolved fluorescence data revealed radiative lifetimes of, typically, a few nanoseconds. Femtosecond transient absorption measurements indicated the formation of triplet states within the first nanosecond of photoexcitation. From the cyclic voltametric studies, the oxidation and reduction processes were found to be ring centered. Spectral changes in the UV–visible absorption were recorded by means of spectro-electrochemical analysis at an applied potential. The DFT and TD-DFT analysis was employed using B3LYP hybrid functional theory and 6-31G­(d,p) basis set in the Gaussian 09 package. The NLO properties of CBZPC1 and CBZPC2 were investigated using the Z-scan technique and femtosecond (fs) pulses with kHz and MHz repetition rates. Closed and open aperture Z-scan data were recorded at three different wavelengths of 600, 700, and 800 nm, and the NLO coefficients were extracted from both types of data. Two-photon absorption (TPA) was the dominant mechanism observed in the open aperture Z-scan data. The real and imaginary parts of the χ(3) along with the two-photon absorption cross sections were evaluated. Our NLO data and large 2PA coefficients and cross sections obtained indicate the potential of these compounds for applications in optical limiting and optical switching applications.

It is common knowledge that poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend, a prototype system for bulk heterojunction (BHJ) solar cells, consists of a network of tens of nanometers-large donor-rich and acceptor-rich phases separated by extended finely intermixed border regions where PCBM diffuse into P3HT. Here we specifically address the photo-induced dynamics in a 10 nm thin P3HT/PCBM blend that consists of the intermixed region only. Using the multi-pass transient absorption technique (TrAMP) that enables us to perform ultra high sensitive measurements, we find that the primary process upon photoexcitation is ultrafast energy transfer from P3HT to PCBM. The expected charge separation due to hole transfer from PCBM to P3HT occurs in the 100 ps timescale. The derived picture is much different from the accepted view of ultra-fast electron transfer at the polymer/PCBM interface and provides new directions for the development of efficient devices.

Antimony(III) halide based zero dimensional hybrids have gained interest as broadband emitters. Until now, quadrangular pyramidal SbX5 based and octahedral SbX6 based 0D hybrids have been reported utilizing different organic...

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A comprehensive investigation is presented on the photophysical and third-order nonlinear optical (NLO) properties of two thioalkyl-substituted tetrathiafulvalene molecules (referred here as G1 and G3) to understand their utility as photosensitizers for dyesensitized solar cell (DSSC) and optoelectronic applications. Both steady-state and time-resolved (in the fs−ns time regime) absorption and photoluminescence (PL) spectroscopy techniques were employed to comprehend the excited-state properties of the molecules in solution as well as in thin films deposited on both quartz and mesoporous TiO 2 layers. The spectroscopy measurements in solution and thin films deposited on quartz provided the excited-state properties of dye molecules. Time-resolved PL measurements at the dye−TiO 2 interface provided initial evidence of electron injection by fast PL quenching decay dynamics for both the molecules. Detailed target analysis of the femtosecond transient absorption spectroscopy (TAS) data of the dye−TiO 2 sample revealed a multistep ultrafast electron injection for both molecules with the fastest injection component being 374 and 314 fs for G1 and G3 molecules, respectively. The ultrafast NLO properties of G1 and G3 were studied using the Z-scan technique with 800 nm, ∼70 fs laser pulses. The open aperture measurements showed three-photon absorption with magnitudes of coefficients 4.7 × 10 −5 cm 3 /GW 2 and 5.2 × 10 −5 cm 3 /GW 2 , and the closed aperture measurements provided second hyperpolarizability (γ) values of 3.5 × 10 −31 esu and 4.2 × 10 −31 esu for G1 and G3, respectively. Additionally, the onset of optical limiting was estimated to be 5.8 × 10 −3 J/cm 2 and 5.7 × 10 −3 J/cm 2 for G1 and G3 molecules, respectively.

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A novel zinc phthalocyanine derivative PBIPC was synthesized by incorporating a triphenyl imidazole moiety at its peripheral positions.