Photoconduction geminate recombination

Influence of EF on magnitude of photoconductivity of fullerene C6o single crystal in a weak MF can be explained in the following way. Increasing intensity of electric field causes the increase of radius of initial distance r0 between the components of electron-hole pairs and, consequently, the decrease of probability of geminate recombination. As a result, AI rises at small values of EF. At higher values of EF the probability of dissociation of pairs in states with uncorrelated spins increases, that causes nonlinear behavior of electrofield dependences of photoconductivity of fullerite C6o in MF. The distance between components of electron-hole pairs in states with uncorrelated spins was estimated as R>3.4 nm. 

Amorphous carbon shows PL after irradiation by heavy ions as described earlier, along with a slow decay of photoconductivity and a distribution of traps. These results indicate that the process is a geminate recombination of carriers that is characterized by rearrangements of carbon atoms by ion irradiation. PL is sensitive to the bonding and structure of the carbon films (e.g., for delocalized states its intensity is several orders higher than for localized states). It was found that the peak energy of PL spectra increases with increase of optical gap [172]. Unirradiated conducting samples prepared at the same temperatures do not show any noticeable PL spectra. Two different peaks, an intense one at around 0.93 eV and a small one... 

Suppose that when a photoconductive polymer is subjected to radiation that is absorbed by the polymer, / free carriers (those that have already escaped geminate recombination) are produced per unit volume per unit time. With constant illumination, the steady-state concentration of free carriers is then no = /r, where r is the average time between generation and recombination of the carrier, the so-called recombination time. For the simple case of a one-signed carrier system, the steady-state photocurrent conductivity a is... 

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