Solution-processed titanium oxide electron injection/transport functional layer in polymer light-emitting diodes

One of the problems limiting the device efficiency of polymer light-emitting diodes is the imbalance of charge injection and transport between the electrons and holes. This problem is particularly serious for the case of aluminum (Al) electrode. By introducing solution-based titanium oxide (TiOx) layer between the polymer and Al electrode, we have demonstrated that the devices exhibit an enhanced efficiency. The TiOx layer reduces the barrier height between the polymer and Al cathode, thereby facilitating the electron injection in the devices and enhancing the device performance. Moreover, we also believe that the TiOx layers prevent the diffusion of metal ions into the emitting polymers during the Al deposition process, reducing the degree of quenching centers in the active polymers.