Free charge injection

FIGURE 1.2. Cyclic voltammetric Nemstian waves for free-moving molecules, a Potential scan for a reduction, b, b Variations of the A ( ) and B (—) concentrations at the electrode surface with time (b) and potential (b ). c, c Current vs. time (c) and potential (c ). d, d Negative charge injected in the solution vs. time (d) and potential (d ). 

As aforementioned, the introduction of carbon nanomaterials is an effective strategy to take on some of the contemporary challenges in the field of DSSCs. In particular, enhanced charge injection and charge transport processes in carbon nanomaterial-doped electrodes, efficient carbon nanomaterial-based, iodine-free, quasi-solid state electrolytes, and the use of novel nanographene hybrids as dyes are some of the most stunning milestones. All of these milestones are considered as solid proof for the excellent prospect of carbon nanomaterials in DSSCs. The major goal of this chapter is to... 

Non-ionic polymer gel, swollen with dielectric solvent, can be extremely deformed as is the case for non-ionic polymer plasticised with non-ionic plasticiser. Instead of the charge-injected solvent drag as a mechanism of the gel actuation, the principle is based on local asymmetrical charge distribution at the surface of the gel18. The mechanism can also be applied to non-ionic elastomers in which the motion of the polymer chain is relatively free. In spite of their many difficulties for practical actuators, polyelectrolyte gels and related materials are the most interesting electroactive polymer materials. 

Polaron Pair State. There are a number of experimental observations which can be interpreted neither by invoking charged excitations injected or photo-generated in the polymer, nor by excitons. However, it may happen that the singlet exciton is broken, as described above, and a pair of charges, negative P and positive P+ polarons, are separated onto adjacent chains, but still bound by the Coulomb attraction. These pairs will be referred to as polaron pairs. Polaron pairs are intermediate states between electronic molecular excitations and free charge carriers. They are formed by excitation of the photo-conductivity in polymers and other molecular solids, as well as... 

Silver halide microcrystals are wide band gap semiconductors which exhibit weak photoconductivity. Early experiments demonstrated that dyes that sensitized silver halide photographic action also sensitized silver halide photoconductivity [6c]. Since the observation of photoconductivity necessitates the movement of free charge within the crystals, dye sensitization processes must inject charge into the silver halide lattice in some way. Initial theories of sensitization were based on the semiconductor view of silver halides, especially as espoused by Gurney and Mott [10]. Current ideas are based on thorough studies of the absorption spectroscopy and luminescence of silver halide emulsions and of adsorbed, sensitizing dyes, and the oxidation-reduction properties of the dyes at silver/silver halide electrodes [11]. 

Some authors claim that in polymers, recombination occurs between free charged polarons, so that the maximum efficiency corresponds to the internal quantum efficiency, ri t the number of photons emitted for every electron injected), as given by... 

Results for a 20 pm thick sample of polycarbonate containing 50 mass% TPD for a field of 1.5 x 107Vm-1 at 296 K with charges injected from an indium tin oxide (ITO) electrode coated with a 0.1 pm thick layer of PPV are shown in Fig. 8.30(b). The limiting current is close to the trap-free SCLC, indicating that the PPV-coated ITO acts as an efficient hole-injecting electrode. The lower curve is the TOF transient recorded under identical conditions. The arrow on the lower curve indicates the transit time and that on the upper curve is 0.8 of this value. The step-voltage response is therefore close to the theoretical prediction. 

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