As a result of intensive research on polymer light-emitting diodes (PLEDs) for the last several years, the device
performances have been remarkably improved. Recently, several researchers reported on a PLEDs with an interlayer
between poly(3,4-ethylenedioxythiophene)-poly-(styrenesulfonate) (PEDOT:PSS) and an emissive polymer. It improved
the device efficiency as well as the device lifetime. The role of the interlayer is to block the electron from back diffusion
to PEDOT:PSS and/or to reduce luminescence quenching at the PEDOT:PSS interface.
We studied the improvement of the PLED by inserting an octadecyltrichlorosilane (OTS) as the interlayer between
PEDOT:PSS and the emissive layer. The OTS was treated on PEDOT:PSS through the self-assembled monolayer (SAM)
process. It improved the device efficiency of the PLED from 3.86 to 4.76 cd/A, and increased the operation lifetime from
270 to 340 minute comparing the non-OTS treated PLED with the OTS treated PLED for 10 min. In blue PLED,
inserting the OTS layer between blue polymer and PEDOT:PSS is promoted hole injection from an anode. Therefore, the
device efficiency is improved, which appears to be due to the increase of balanced recombination as a result of the
accumulated electrons near the interface between emissive layer and PEDOT:PSS.