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A resistive memory device using organo metal halide perovskite (CH3NH3PbBr3) quantum dots sandwiched between two PMMA layers with a very low SET/ RESET voltage and operating current is demonstrated in this paper. Because of the low operating voltages and currents, the operating power of the perovskite quantum dot memory device is very low. Perovskite quantum dots were prepared using the chemical method, namely ligand assisted reprecipitation method. It was then incorporated into PMMA to form a quantum dot - polymer composite. The composite was sandwiched between two PMMA layers by a successive spin coating technique. The SET voltage of the resulting device was low ∼10 mV. Operating current of the device was in micro ampere range. Hence the operating power of the device was very low and was of the order of 1 micro watt. ON/OFF current ratio of 10 was obtained for the fabricated memory device. The difference between resistances at ON and OFF states was ∼400 ohms under positive bias and ∼180 ohms under negative bias.

In the present work, carbon nanotubes were synthesized from methane by an in-house chemical vapor deposition (CVD) system. A thin film of nickel (Ni) of thickness 11 nm was deposited over a quartz substrate by RF-sputtering and used as the catalyst in the CNT growth. The catalyst film was annealed at 850°C for 45 minutes in H2 and Ar atmosphere for the island formation of Ni nanoparticles which initiate the CNT growth. The deposition was performed at 850°C for 30 minutes in low pressure. Raman spectra confirmed that the synthesized CNTs are multiwalled in nature. Synthesized CNTs have a diameter in the range of 40 – 50 nm. These synthesized CNTs can be used for various electrode applications in optoelectronic devices.

In the present paper, we report the development of solution processed Carbon Nano-Tube (CNT) and PEDOT:PSS composite for application in c-Si – organic heterojunction solar cell as hole selective layers. The PEDOT:PSS CNT composite film shows high conductivity and has high optical transparency. The CNT network in the composite film will act as a carrier transport bridge between the PEDOT:PSS domains. Also, the CNT will act like stress centers preventing the breakage of transport path of carriers in composite film, making the CNT-PEDOT:PSS composite an excellent candidate as hole selective layer in flexible solar cells. Thus, the CNT-PEDOT: PSS composite can considerably enhance the performance of CNT-PEDOT: PSS /n-Si solar cells through the synergistic properties of CNT and PEDOT:PSS. The power conversion efficiency of the as-designed solar cell was 9.24% with an open circuit voltage of 576 mV. Dopant-free double heterojunction solar cell making use of MgF2 electron transport layer was also fabricated.

In the present study, the field effect behavior of graphene films grown in a home-built CVD system was analyzed by fabricating graphene field effect transistor (GFET). Under the electrostatic effect of applied gate voltage, graphene films showed unipolar behavior (p-type) in transfer characteristics when the device is kept in air. A unipolar to bipolar conversion was observed with GFET transfer characteristics while performing measurements in vacuum. The decreased electron-hole symmetry was observed and it is a deviation from ideal characteristics. The hole mobility was 510 cm2V-1s−1 for measurements carried out in air. Later, with ambipolar behavior, the films showed a hole mobility of 455 cm2V-1s−1 and an electron mobility of 143 cm2V−1s-1.

Surface enhanced Raman spectroscopy (SERS) is a sensitive detection technique where the Raman signal from molecules, when adsorbed on the surface of metal nanoparticles, gets enhanced to an order of 1012.. In the present work, silver nanowires are fabricated via solvothermal method and attached to the tip of optical fiber. SERS is measured from the tip of optical fiber in direct sensing mode, using Rhodamine 6G as probe molecule. The fabricated SERS substrate could detect molecules with a detection limit of 10−12 M. Multi-analyte detection capability of SERS substrate based optical fiber is also determined by detecting crystal violet.

Graphene has generated enormous research interest during the last decade due to its significant unique properties and wide applications in the field of optoelectronics and photonics. This research studied the structural and nonlinear absorption properties of reduced graphene oxide (rGO) synthesized by Modified Hummer’s method. Structural and physiochemical properties of the rGO were explored with the help of Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy (Raman). Nonlinear absorption property in rGO, was investigated by open aperture Z-scan technique by using a continuous wave (CW) laser. The Z-scan results demonstrate saturable absorption property of rGO with a nonlinear absorption coefficient, β, of −2.62 × 10−4 cm/W, making it suitable for applications in Q switching, generation of ultra-fast high energy pulses in laser cavity and mode lockers.

Transparent conducting films are becoming increasingly interesting because of their applications in electronics industry such as their use in solar energy applications. In this work silver nanowires were synthesized using solvothermal method by reducing silver nitrate and adding sodium chloride for assembling silver into nanowires. Absorption spectra of nanowires in the form of a dispersion in deionized water, AFM and SEM images confirm the nanowire formation. Solution of nanowire was coated over PET films to obtain transparent conducting films.

Upconversion luminescence is an interesting area while considering its applications in a vast variety of fields. Rare earth ions like erbium is the most studied and efficient candidate for achieving upconversion. Erbium and ytterbium co-doped ZnO nanoparticles were prepared through co-precipitation method. A strong red emission has been obtained while exciting with 980 nm laser. Dependence of luminescence emission colour on ytterbium concentration has been studied.