page_title: Photoconductive polymer
section_title: Charge trapping
hierarchical_section_title: Photoconductive polymer / Charge trapping
caption_attribution_description: English: Charge immobilization due to a redox-irreversible side-reaction
context_page_description: Photoconductive polymers absorb electromagnetic radiation and produce an increase of electrical conductivity. Photoconductive polymers have been used in a wide variety of technical applications such as Xerography and laser printing. Electrical conductivity is usually very small in organic compounds. Conductive polymers usually have large electrical conductivity. Photoconductive polymer is a smart material based on conductive polymer, and the electrical conductivity can be controlled by the amount of radiation.
  The basic parameters of photoconductivity are the quantum efficiency of carrier generation, the carrier mobility, electric field, temperature, and concentration of charge carriers. The intrinsic properties of photoconductive polymers are the quantum efficiency and carrier mobility, which will determine the photocurrent. Photocurrent will be effected by these four kinds of processes: charge-carrier generation, charge injection, charge trapping, charge carrier transport.
  Hundreds of photoconductive polymers have been disclosed in patents and literature.
context_section_description: Charge trapping is an important processes, in which migrating charges can be immobilized in trap sites. If the traps are 'shallow', they may be referred to as 'transportinteractive'.  Hole trapping materials usually have lower oxidation potentials and work as host-transporting materials. Stronger electron acceptor have better ability to trap transport electron.
  
  Charges can be immobilized by redox-irreversible side-reactions due to the geminate recombination and recombination of carriers in the circuit. In this process, charged moiety can be illustrated by the scheme:
  (a) The redox steps to achieve trap-free migration of a hole involving neutral groups M and charged groups M+  
  (b) The intermittent species Mⱼ⁺ can undergo two kinds of process:
  (i) The migration of electron from Mₖ will result in forming Mⱼ coming from Mⱼ⁺
  (ii) Mⱼ⁺ undergo a side-reaction leading to a charged species X⁺ that won't further exchange the charge with the neighboring group M.
caption: (b)Charge immobilization due to a redox-irreversible side-reaction
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