ИСТИНА

Thin films of polyaniline (PANI) and poly-3,4-ethylenedioxythiophene (PEDOT) complexes with water-soluble sulfonated polyelectrolytes of various structure were formed electrochemically in galvanostatic regime. The layers were used as a transparent hole-transport layer (HTL) in hybrid solar cells (HCSs) where CH3NH3PbI3 layer of perovskite structure served as a photoactive layer (Fig.1). For the fabrication of HCS devices, an electrochemical polymerization technique is preferable, since it is a single-step process providing thin films with controlled thicknesses and morphology. The latter is important as it determines the structure and quality of interface with subsequent layers. The poly-(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA) and poly(styrene sulfonic acid) (PSSA) and their sodium salts (in the case of PEDOT) were chosen as polyelectrolytes. They are characterized by good film-forming properties, optical transparency and high ionic conductivity that allowed performing PANI or PEDOT electropolymerization without supporting electrolyte. Thin bilayer HTLs were also prepared by electrochemical layer-by-layer deposition of PANI-polyelectrolyte and PEDOT-polyelectrolyte complexes. The HTL energetic parameters were obtained from cyclic voltammetry measurements. Highest occupied molecular orbital (HOMO) energy values were calculated from correlation between the Fermi energy level and the half-wave potential. HOMO levels of all the HTLs were found to match well to the valence band edge of the photoactive layer of CH3NH3PbI3 (-5.4 eV), so holes are easily transferred from the CH3NH3PbI3 layer to the HTL and further to ITO electrode in the HCS devices. The power conversion efficiency of the devices ranged between 8 and 11%. The efficiency of the HCS devices was found to depend on the composition of the polymer-polyelectrolyte complexes and the structure of the polyelectrolyte. In particular, for PEDOT, the nature of polyelectrolyte cation influenced the HCS characteristics as well. The photovoltaic behavior is discussed considering that the formation of HTLs is defined by the aniline and EDOT molecules distribution in the synthesis solution. The distribution, in turn, depends on the hydrophobicity and conformation of the polyelectrolyte macromolecules.