hi, Jaehyun,

The first of all, PEDOT:PSS are semi-metallic mixture of polymers, which normally it energy is described as work function, similar to metals' ones. The work function of PEDOT:PSS films could be slightly varied from 4.9eV to 5.1eV. It very much depends which type of commercial PEDOT:PSS you use and the ratio of PEDOT to PSS as well as dopants into the PEDOT:PSS ink formulation.

The graphs of JV for ITO/PEDOT:PSS/Al you show could come from the morphology of PEDOT:PSS films if the film thickness is more or less the same. The pin holes on the films or uneven films can generate a spike on your JV curves. Therefore, it is sensible to record the film qualities such as roughness using AFM.

Hope it helpss

Very best

Xuhua

Hello Kim,

The observed spikes in JV curves is due to poor interfaces between electrode and oragnic laye at particular local points. These poor interfaces are due to pin holes and uneven surface of PEDOT:PSS. So, first try to optimize PEDOT:PSS film with minimum roughness .

What is the polarity of the applied voltage? You have to measure the I-V characteristics of the your ITO/ PEDOT:PSS/ Al structure in both directions. According to the energy levels of the different materials it must form a rectifying contact with Aluminum as a cathode and the ITO as anode.

So, theoretically you may get a rectifying diode. It seems that you displayed the reverse characteristics with anode at lower potential than the cathode.

as the electrodes defined above.

The instability in the I-V curve is due to the non homogeneous distribution of the current through the device. This leads to localized heating at high voltage and current and burning the conducting areas which render the device off. This explains the top curve. The bottom curves the current is more homogeneously distributed.

Best wishes

thank you for your helps! it was great helps.