Hot Carrier-Assisted Intrinsic Photoresponse in Graphene Gabor, Nathaniel M.; Song, Justin C. W.; Ma, Qiong ...
Science (American Association for the Advancement of Science),
11/2011, Volume:
334, Issue:
6056
Journal Article
Peer reviewed
Open access
We report on the intrinsic optoelectronic response of high-quality dual-gated monolayer and bilayer graphene p-n junction devices. Local laser excitation (of wavelength 850 nanometers) at the p-n ...interface leads to striking six-fold photovoltage patterns as a function of bottom-and top-gate voltages. These patterns, together with the measured spatial and density dependence of the photoresponse, provide strong evidence that nonlocal hot carrier transport, rather than the photovoltaic effect, dominates the intrinsic photoresponse in graphene. This regime, which features a long-lived and spatially distributed hot carrier population, may offer a path to hot carrier-assisted thermoelectric technologies for efficient solar energy harvesting.
An 8.5-Gb/s single-chip optoelectronic integrated circuit (OEIC) for short-distance optical communications is realized in a 0.13-μm CMOS process. The OEIC consists of an on-chip silicon photodiode, a ...transimpedance amplifier with modified regulated cascode input configuration, an adaptive equalizer based upon slope-detection algorithm, and a limiting amplifier with merged negative impedance circuits. The proposed slope-detection adaptive equalizer compensates the limited bandwidth and the temperature variation of the integrated silicon photodiode. Measured results demonstrate 120-dB Ω transimpedance gain, 5.9-GHz bandwidth, -3.2-dBm optical sensitivity for 10 -12 BER, and 47-mW power dissipation from a single 1.5-V supply. The OEIC chip core occupies the area of 0.1 mm 2 .
We report on the hybrid integration of silicon-on-insulator slot waveguides with organic electro-optic materials. We investigate and compare a polymer composite, a dendron-based material, and a ...binary-chromophore organic glass (BCOG). A record-high in-device electro-optic coefficient of 230 pm/V is found for the BCOG approach resulting in silicon-organic hybrid Mach-Zehnder modulators that feature low U π L-products of down to 0.52 Vmm and support data rates of up to 40 Gbit/s.
A roll-to-roll process enabling fabrication of polymer solar cells comprising five layers on flexible substrates is presented. The device geometry is inverted and allow for fabrication on both ...transparent and non-transparent flexible substrates. The process is illustrated in this work by formation of a bottom electrode comprising silver nanoparticles on a 130 micron thick polyethyleneternaphthalate (PEN) substrate. Subsequently an electron transporting layer of zinc oxide nanoparticles was applied from solution followed by an active layer of P3HT-PCBM and a hole transporting layer of PEDOT:PSS. These first four layers were applied by slot-die coating. The final electrode was applied by screen printing a grid structure that allowed for transmission of 80% of the light. The materials were patterned into stripes allowing for formation of a single cell device and serially connected modules comprising 2, 3 and 8 stripes. All five layers in the device were processed from solution in air and no vacuum steps were employed. An additional advantage is that the use of indium-tin-oxide (ITO) is avoided in this process. The devices were tested under simulated sunlight (1000
W
m
−2, AM1.5G) and gave a typical performance 0.3% in terms of power conversion efficiency (PCE) for the active layer. The low PCE was due to poor transmission of light through the back electrode.
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