Hardeep Singh Gill

Synthesis and Sensing Applications of Fluorescent 3-Cinnamoyl Coumarins.

We have synthesized two novel fluorescent 3-(4-diethylaminocinnamoyl) coumarins that exhibit fluorescence quenching upon exposure to a nerve agent simulant, diethylchlorophosphate (DCP), providing a basis for rapid and sensitive DCP chemosensing. Furthermore, these coumarin derivatives display two-photon fluorescence upon illumination with near-infrared laser pulses and their two-photon (TP) absorption cross-section was evaluated. The potential for TP bio-imaging of these compounds was investigated by their cellular uptake in HeLa cells by TP confocal microscopy.

Solution processed flexible planar hybrid perovskite solar cells

Organolead halide perovskites are attracting considerable attention for applications in high performance and flexible hybrid photovoltaic devices. Low temperature solution-processed flexible hybrid solar cells with CH3NH3PbI2Cl, using [6,6]-Phenyl C61 butyric acid methyl ester (PCBM) and Poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt- (benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT) as electron transport materials were fabricated on ITO coated plastic substrates in planar configuration. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate was employed as the electron blocking layer. Under standard AM 1.5G solar irradiation, these flexible solar cells yielded power conversion efficiencies of 5.14% and 7.05% with the electron transporting materials PCBM and F8BT, respectively.

Performance enhancement of fullerene based solar cells upon NIR laser irradiation

Photovoltaic performance enhancement of fullerene based solar cells was achieved upon exposure to near-infrared (NIR) laser pulses. The solar cells were fabricated with poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) under ambient conditions. The cells were then post-treated with NIR femto-second laser pulses at 800 nm for different intervals of time. An enhancement of 50% in the power conversion efficiency was achieved for the devices with 15 minutes of NIR laser irradiation compared to that of the control device. The enhancement in the power conversion efficiency is attributed to the formation of a covalent linkage between P3HT and PCBM as suggested by Matrix-assisted laser desorption/ionization time of flight mass spectroscopic analysis on a blend of a thiophene oligomer and PCBM before and after NIR laser exposure.

Effects of Nanoimprinted Structures on the Performance of Organic Solar Cells

The effect of nanoimprinted structures on the performance of organic bulk heterojunction solar cells was investigated. The nanostructures were formed over the active layer employing the soft lithographic technique. The measured incident photon-to-current efficiency revealed that the nanostructured morphology over the active layer can efficiently enhance both light harvesting and charge carrier collection due to improvement of the absorption of incident light and the buried nanostructured cathode, respectively. The devices prepared with the imprinted nanostructures exhibited significantly higher power conversion efficiencies as compared to those of the control cells.

SU-E-CAMPUS-I-01: Nanometric Organic Photovoltaic Thin Film X-Ray Detectors for Clinical KVp Beams

PURPOSE To fabricate and test nanometric organic photovoltaic (OPV) cells made of various active-layer/electrode thicknesses and sizes; to determine the optimal material combinations and geometries suitable for dose measurements in clinical kilovoltage x-ray beams. METHODS The OPV consisted of P3HT:PCBM photoactive materials sandwiched between aluminum and Indium Tin Oxide (ITO) electrodes. Direct conversion of xrays in the active layer composed of donor and acceptor semiconducting organic materials generated signal in photovoltaic mode (without external voltage bias). OPV cells were fabricated with different active layer thicknesses (150, 270, 370 nm) and electrode areas (0.4, 0.7, 0.9, 1.4, 2.6 cm2 ). A series of experiments were preformed in the energy range of 60-150 kVp. The net current per unit area (nA/cm2 ) was measured using 200 mAs time-integrated beam current. RESULTS The net OPV current as function of beam energy (kVp) was proportional to ∼E0,45 when adjusted for beam output. The best combination of parameters for these cells was 270 nm active layer thicknesses for 0.7 cm2 electrode area. The measured current ranged from 0.69 to 2.43 nA/cm2 as a function of x-ray energy between 60 and 150 kVp, corresponding to 0.09 - 0.06 nA/cm2 /mGy, respectively, when adjusted for the beam output. CONCLUSION The experiments indicate that OPV detectors possessing 270 nm active layer and 0.7 cm2 Al electrode areas have sensitivity by a factor of 2.5 greater than commercial aSi thin film PV. Because OPV can be made flexible and they do not require highvoltage bias supply, they open the possibility for using as in-vivo detectors in radiation safety in x-ray imaging beams.