Organic light-emitting FET having pyrene derivatives as an active layer and the operation mechanism

We report on bright electroluminescence (EL) from 1wt%-rubrene doped tetraphenylpyrene (TPPy) as an active layer in an organic light-emitting field-effect transistor (OLEFET), demonstrating that TPPy provides compatibility of both transistor and EL characteristics. We observed a maximum EL quantum efficiency (η_ext) of ∼0.5% with a Cr/Au source-drain electrode and slightly higher η_ext of ∼1% with the source-drain (S-D) electrodes of Au/low-work-funotion metal multi-layers aiming for simultaneous hole and electron injections. In these devices, source (V _s), drain (V_d) and gate (V_g) voltages significantly influenced on hole and electron injection and accumulation. In order to elucidate detailed EL mechanism of the OLEFET device, we investigated carrier recombination and emission sites by local doping method. We inserted an ultra-thin rubrene doped TPPy layer (10 nm) in a TPPy active layer (80 nm) and measured the luminance (L)-drain current (I_d)-V_d characteristics and EL spectra by changing V_g. We demonstrate that the local doping method is a useful technique for estimating width of the carrier recombination and EL emission site in OFET devices.