Photo charge carrier generator

Amorphous selenium metal was originally used as the photoconductor (photo charge carrier generator) of the Carlson process in electrophotographic reprography. Because of its toxicity and difficulty of fabrication, selenium was then replaced by organic photoconductor materials (OPC). 

Fig. 9.26 Temporal characteristics of photo-induced absorptions associated with charge carriers generated by short laser pulses, (a) IR absorption in MEH-PPV (reprinted from Moses et ah, 2001 copyright 2001, with permission from Elsevier) and (b) optical absorption in a poly(indenofluor-ene) (reprinted from Silva et ah, 2001 copyright 2001, with permission from Elsevier). See text for details.

Problem 8.2. Photo-induced charge-carrier generation in conjugated polymers ... 

Binh, N. T., Gailberger, M., and Bassler, H., Photo-conduction in poly(3-alkylthiophene) I. Charge carrier generation, Synth. Met., 47, 77, 1992. 

The limiting factors that control photocatalysis efficiency are rapid recombination between photo-generated charge carriers, and the backward reaction leading to recombination of the formed molecular hydrogen and oxygen. To retard these processes efforts have typically focused on surface modification of the semiconductor particles using metals or metal oxides. 

This effect is characterized by light-induced formation of a photo-emf in boundary layer-free systems 8>10>. It is necessary for the generation of the Dember emf to have (a) the formation of a concentration gradient of charge carriers resulting from non-uniform illumination, and (b), electrons and holes of different mobilities ... 

Photo-detector regions are formed in JP-A-1205476 by laser annealing a multi-layer structure of HgTe and CdTe. Radiation which has generated charge carriers between two detector elements will be absorbed in the multi-layer structure thereby reducing cross-talk. 

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... 

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