No abstract

We report on red phosphorescent trilayer organic light-emitting field-effect transistors (LEFETs), which exhibit ambipolar transport characteristics but strong emission in the unipolar hole regime, with an exceptionally wide recombination zone of 60–70 µm and a maximum external quantum efficiency of 0.21%. From the results of detailed electroluminescence characterization, we clarify how the energy-level matching condition and transport geometry of the heterostructure govern the charge distribution and recombination, and affect the overall device performance.

A proper design of the injection barrier between a source electrode and an active layer is essential to achieve high-performance vertical organic field-effect transistors (VOFETs). Here, we show that a modification of metallic source electrodes with thiol-based self-assembled monolayers (SAMs) is effective in controlling the electrode work function and injection barrier into the active layer, leading to a significantly reduced off-current and undegraded on-current in an optimized VOFET. For the studied C60 VOFETs with Ag electrodes, the on/off ratio improves from <10 to 103–104 when the injection barrier is varied from 0.02 to 0.33 eV by SAM modification.