Spectroscopy of local states in molecular materials using space-charge-limited currents

Steady-state space-charge-limited (SCL) currents in insulators and wide-bandgap semiconductors are reviewed. Methods of deriving asymptotic analytical expressions describing SCL current-voltage characteristics are briefly analysed. Direct methods of determination of densities of local states in spatially homogeneous samples are discussed. The use of derived equations to determine parameters of the density-of-states functions is illustrated with experimental results obtained on single crystals and polycrystalline thin films of phthalocyanines.