Charge collection

Recently, uniform Filins with high concentrations of Cwl were cast from 1,2-dichlorobenzene solutions containing up to 1 4 weight ratio MEH-PPV [110]. For devices made from these high concentration blends, charge collection efficiencies around //,.=26% (electron/incident photon) and power conversion efficiencies around tjc-2.5% (electrical power out/incident light power) have been realized. 

The Gartner model simulates charge collection by a potential-dependent space charge layer and considers diffusion into the space charge layer of charge carriers generated deep inside the semiconductor. The well-known Gartner formula for the photocurrent /ph is... 

Charge collection. Electric fields within the photosensitive material collect charge into pixels. The detector can be designed to collect either electrons or holes. 

The short penetration depth of UV/blue photons is the reason that frontside CCD detectors have very poor QE at the blue end of the spectrum. The frontside of a CCD is the side upon which the polysilicon wires that control charge collection and transfer are deposited. These wires are 0.25 to 0.5 /xm thick and will absorb all UV/blue photons before these photons reach the photosensitive volume of the CCD. For good UV/blue sensitivity, a silicon detector must allow the direct penetration of photons into the photosensitive volume. This is achieved by turning the CCD over and thinning the backside until the photosensitive region (the epitaxial layer) is exposed to incoming radiation. 

Thorium. Multiple-collector measurement protocols by TIMS for thorium isotopic analysis typically involve the simultaneous measurement of Th and °Th (for silicate rocks), or Th and °Th, then Th and Th (for low- Th samples), using an axial ion counter and off-axis Faraday collector (Table 1). Various methods are used to correct for the relative gain between the low-level and Faraday detectors and 2a-uncertainties of l-5%o are typically obtained (Palacz et al. 1992 Cohen et al. 1992 McDermott et al. 1993 Rubin 2001). Charge-collection TIMS protocols enable Th, °Th and Th to be monitored simultaneously on a multiple-Faraday array and can achieve measurement uncertainties at the sub-permil level (Esat et al. 1995 Stirling et al. 1995). 

In the past three years, MC-ICPMS has emerged as an alternative to TIMS for precise measurement of the U-series isotopes with comparable or better precision. U-Th isotopes can now be routinely measured at the sub-permil level. Previously, this had only been demonstrated using charge-collection TIMS applied to thorium isotope measurement. Data collection efficiency, sample size requirements, and detection limits can also be greatly improved over TIMS. For the U- U- Th system applied to carbonate samples, this has extended the dating range beyond 600,000 years, and °Th-age uncertainties of 2000 years are now attainable on 300,000 year-old samples (e g., Stirling et al. 2001). 

Even for charge collection (Esat 1995) instead of cnrrent amplification, thongh in the former case the magnitnde is mnch less. 

Esat TM (1995) Charge collection thermal ion mass spectrometry of thorium. Int J Mass Spectrom Ion Proc 148 159-170... 

To be able to detect a single particle, the number of ions produced must be increased. As voltage is increased into the proportional region, the primary ions acquire enough energy to cause secondary ionizations (gas amplification) and increase the charge collected. These secondary ionizations may cause further ionization. 

A new generation of detectors has been developed with NbSi thin-film sensors (instead of the NTD sensors for present detectors). Each detector consists of a Ge crystal with two NbSi sensors acting also as electrodes for charge collection. These thin-film sensors are sensitive to the athermal component of the phonon signal, acting as near-surface interaction tag [49],... 

Relatively little is understood in the presence of non planar-non ideal interfaces, where electronic levels located in the band gap region act as recombination centers. Colloidal materials, low cost polycrystalline materials and films, interpenetrating networks of absorber and charge collecting phases (e.g., as in the DSSC cells), and the presence of redox active adsorbing species, all give rise to... 

The observation of pores in the anodic oxide with a density in the order of 1011 cnT2 [Agl] supports the so-called fluctuating pore model [Lel3]. This model assumes that randomly distributed pores in the oxides work as charge collecting centers, which lead to oscillations synchronized by the applied external electric field. It should be noted that the observed pore density corresponds well with the roughness at the oxide-electrolyte interface observed after the stress-induced transition of an anodic oxide, as shown in Fig. 5.5. 

Zhu, K. Neale, N. R. Miedaner, A. Frank, A. J. (2007) Enhanced charge-collection efficiencies and light scattering in dye-sensitized solar cells using oriented Ti02 nanotubes arrays. Nano Letters 7 69-74... 

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