I was trying to create LED with carbon quantum dot as a emitting layer. But, i want to used PEDOT:PSS as the anode, which typically used as Hole Transport layer. The structure of the LED is, PEDOT:PSS/PVK/PVK:CQDs/Ag. i didnt yet measuring work function or band-gap for each film. Instead, i have already do simple measurement like FTIR, Sheet resistance and optical spectroscopy.

Sheet resistance for PEDOT:PSS after solvent treatment is increased from ~300 ohm/sq to ~70 ohm/sq. For the Ag, the result is around 10 ohm/sq. Meanwhile, the CQDs show perfectly fine in PL around ~650 nm, which show that CQDs has Photoluminescence mechanism.

But, the problem is happen when the film stacked into one device, where there no electroluminescence mechanism happen. If Led usually has reverse bias, this device hasnt this behavior. Whenever i change the voltage orientation its still conducting. I think the device behave more like resistor rather than diode. is this mean the work function didnt match between PEDOT:PSS and Ag

So another question is "is all CQDs that has PL mechanism can be deposited into emissive layer in LED?"

bellow, i have attached the image how it look of PVK:CQDS formed on PEDOT:PSS under UV Light condition