Time-resolved morphological study of ‘PEDOT:PSS’ hole transporting layer for polymer solar cells

The reliability of the polymeric hole transport layer poly(3,4-ethylenedioxythiophene):poly(styrenesulphonate) (PEDOT:PSS), used in organic photovoltaic and single carrier diodes was addressed. The morphological properties of the blend were monitored during thermal treatments and under controlled humidity condition. The approach adopted, relying on joint use of in situ energy dispersive X-ray reflectivity (EDXR) and atomic force microscopy (AFM) techniques, allowed to observe, in real time, the occurrence of degradation phenomena related to both bulk and interface effects. Additionally, Fourier transform infrared (FTIR) spectroscopy experiments provided information on the chemical properties correlated to the blend morphological modifications. The overall approach allowed to identify aging process that may compromise the chemical–physical characteristics of the PEDOT:PSS hole conducting layer and, in turn, may have a relevant impact on the performances of the organic devices.