The photo-induced electron and hole transfer across the semiconductor-dielectric interface in trap-dominated $p$-type organic field-effect transistors has been investigated. It has been observed that the transfer of electrons into the dielectric results in a decrease of the field-effect mobility of polarons, suggesting that additional shallow traps are generated in the conduction channel. Using this effect, the dependence of the field-effect mobility on the density of shallow traps, $\mu (N)$, has been measured, which allowed us to estimate the average polaron trapping time, ${\tau }_{\mathrm{tr}}=50\pm 10\mathrm{ps}$, and the density of shallow traps, $N_0=(3\pm 0.5)\times {10}^{11}{\mathrm{cm}}^{-2}$, in the channel of single-crystal tetracene devices.

• Received 29 September 2006

DOI:https://doi.org/10.1103/PhysRevLett.98.096402