Photoanodes based on titanium dioxide (TiO2) are ubiquitous in various molecular devices for solar energy conversion and storage.[1] Lanthanide doping of TiO2 (LTO) is among the most explored materials with tremendous potential towards efficient charge transport mesoporous layer as well as improving the photocatalytic activity in both solar cell and solar fuel devices.[2, 3] In this work, presented a comprehensive investigation of improved performance of Samarium (Sm3+)-doped TiO2 based dye-sensitized solar cells (DSSC) and Photo-electrochemical (PEC) devices and established the optimum Sm3+ doping of TiO2 by characterizing the different Sm3+concentrations (0.1-0.5 mol%). Various techniques, namely, X-ray diffraction (XRD), scanning electron microscope (SEM), UV-VIS absorption spectroscopy, are employed for an all-inclusive characterization of the prepared Sm-TiO2 samples. The dielectric measurements on Sm-TiO2 pellets established the best electrical conductivity exhibited by Sm (0.4%)-TiO2. Synthesis protocols are followed based on earlier work.[3] The photoanodes based on prepared Sm-TiO2 are deposited on FTO substrates and are used to fabricate DSSC and PEC devices. Commercial N719 dye-based DSSC devices are fabricated and tested. Devices with Sm(0.3%)-TiO2 exhibited power conversion efficiency (η) ≈ 6.4%, which is almost 100% improvement on devices with undoped-TiO2 that exhibited η: 3.4% as shown in Figure 1. Time-resolved PL-quenching measurements evidenced better electron-injection at dye/Sm (0.3%)-TiO2 interface. Similarly, PEC devices presented higher current density at 1.2 V vs RHE potential for Sm (0.3%)- TiO2. This enhancement corroborates the EIS measurements presenting lower charge transfer resistance values for devices with Sm (0.3%)-TiO2.
Herein, results from the investigation of ultrafast photophysical and third-order nonlinear optical properties of newly synthesized Zn phthalocyanine, namely [Zinc (II) 2,10,16,24tetrakis(2,6-dichloropyridin-3-yl) phthalocyanine, PyCl2PC] molecule are presented. The photophysical properties were studied using femtosecond transient absorption spectroscopy while the NLO properties were measured using the single beam Z-scan and degenerate four-wave mixing (DFWM) techniques. The transient absorption spectra were obtained at 400 nm photoexcitation and a white light continuum probed the corresponding dynamics from (440-780 nm) in the solution phase. The obtained transient absorption spectra were globally fitted using a kinetic model which yielded the different photophysical constants after photoexcitation such as (i) internal conversion from higher electronic excited state (Sn) to lower electronic state (S1) happening in 1 ps (ii) Vibrational relaxation (6.25 ps) occurring within the S1 states (III) Intersystem crossing (1.78 ns) (IV) relaxation from the triplet states to ground state (0.11 μs). Nonlinear absorption properties were measured at 800 nm wavelength utilizing ~70 fs, 1 kHz laser pulses in the solution phase. A large two-photon absorption coefficient (β) of ~8×10-13 cm/W was obtained and the corresponding cross-section was estimated to be 659 GM. Time-resolved degenerate four-wave-mixing measurements revealed a large magnitude and an ultrafast response of χ(3).
Conference Committee Involvement (4)
Recent Advances in Optical Sciences
6 May 2016 |
Optical Nanostructures and Advanced Materials for Photovoltaics (PV)
2 December 2014 |
Optical Instrumentation for Energy and Environmental Applications (E2)
3 November 2013 |
Optical Instrumentation for Energy and Environmental Applications (E2)
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