Studies of photogenerated charge carriers from donor-acceptor interfaces in organic field effect transistors. Implications for organic solar cells

Bilayer organic field effect transistor (OFET) structures consisting of an optically active electron donor (D) and an electrically active electron acceptor (A) system offer a quantitative device tool for characterizing photoinduced charge transport processes. Here, we report an investigation of the photoinduced response of a bilayer OFET fabricated from a naphthalene-bis(dicarboximide)- based polymer (N2200) as the n-channel A transport layer and a p-channel regioregular poly-3-hexylthiophene (P3HT) top D layer. This FET exhibits characteristic steady-state spectral response as well as transient profiles as a function of the gate voltage (V_g), yielding valuable information on bulk and interfacial charge transport properties. Thus, the derived N2200 electron mobility is shown to be in good agreement with bulk measurements (significantly greater than that of PCBM), and the N2200/P3HT interface is shown to be a highly efficient structure for charge transfer and free carrier generation.