Interpretation of trap-limited mobility in space-charge limited current in organic layers with exponential density of traps

Abstract

Charge carrier transport in disordered organic semiconductors, performed in electronic devices such as optoelectronic and photovoltaic ones, is usually affected by an exponential distribution of localized states in the band-gap (traps) under space-charge limited current. In this paper, we provide a full analysis for the trap-controlled transport of the single-carrier device in the frequency domain. Trap-limited mobility is interpreted in terms of the classical multiple-trapping picture with one transport state and the trapping-detrapping dynamics of the exponential density of traps. This allows us to provide a suitable explanation of the usual experimental features of the mobility dependence on voltage as along with the capacitance spectra.