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Field Dependence of Exciton‐Induced, Contact‐Limited Photocurrents in Molecular Crystals
Author(s) -
Killesreiter H.,
Baessler H.
Publication year - 1972
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220530120
Subject(s) - exciton , photocurrent , dissociation (chemistry) , crystal (programming language) , condensed matter physics , materials science , chemical physics , chemistry , molecular physics , physics , optoelectronics , computer science , programming language
The current–field dependence of contact‐limited photocurrents resulting from dissociation of Frenkel excitons at the interface between molecular crystals and a metal or a fatty acid layer is investigated. In the field range 3 × 10 3 Vcm −1 < F < 10 5 Vcm −1 both photocurrent and dark current follow a j = j 0 (1 + bF ) relationship with no indication of a field‐independent limiting current. An explanation is given in terms of the Onsager model for thermally activated diffusional escape of a carrier inside the crystal from the attractive Coulombic potential of its countercharge. At higher fields the Frenkel‐Poole effect becomes operative. It is concluded that exciton dissociation initially produces a thermalized carrier inside the crystal.