Electronic properties of hybridized poly (3, 4-ethylenedioxythiophene): Polystyrene sulfonate with surface-capped CdSe nanocrystals

The chemical state and electronic properties of hybrid material based on poly (3, 4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) and pyridine-capped CdSe nanocrystals have been investigated using photoemission spectroscopy, near-edge x-ray absorption fine structure, and ultraviolet photoelectron spectroscopy. With a high dipole moment as well as high physical momentum, CdSe nanocrystals hindered the rearrangement of PEDOT:PSS and induced PSS-rich surface during film formation. Thus, the work function value was decreased by dedoping of PEDOT or charge localization in PEDOT. Through heat treatment, the behavior of π - π transition in C 1s and the work function value was nearly restored, gradually; these mean recovery of electrostatic bonding nature between PEDOT and PSS. However, the ionization potential (IP) was slightly increased by 0.3 eV with CdSe nanocrystal incorporation and interpreted as dielectric property and local electron transfer from highest occupied molecular orbital of PEDOT to valence band of CdSe nanocrystals. Subsequent addition of CdSe nanocrystal and degree of capping with pyridine allows for a well-controlled electronic structure of PEDOT:PSS, work function, and IP.