i was fabricated PHOLED solution device. but However, the device does not operate normally.

The quantum yield of the emitter is ~ 90% but less than 2% in the device.

The conditions of the device

PEDOT: PSS: 40 nm

PVK (0.3 wt% in chlorobenzene): 30 nm

EML (mCP: dopant (15%) in toluene) 30 nm

TmPyPB 35 nm

Liq 1 nm

Al 1500 nm.

First, the problem is that the current density is very low.

Second, as the voltage increases, the second peak in the EL spectrum gradually increases. I think the exciton recombination zone is moving.

Which layer should I adjust to make the device work normally?

In my personal opinion, we are going to turn the Host into a bipolar host.

thanks