Effects of organic inorganic hybrid perovskite materials on the electronic properties and morphology of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and the photovoltaic performance of planar perovskite solar cells

Abstract

Perovskite solar cells (PSCs) have attracted considerable attention because of their low fabrication cost and impressive energy conversion efficiency. The perovskite layer of planar PSCs is usually prepared by coating a solution of perovskite precursors, that is, PbI₂, PbCl₂ and methylammonium iodide (MAI), on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS, Clevios P VP Al 4083). Here, the deposition of the perovskite layer from its precursor solution saliently affects the electronic structure and properties of PEDOT:PSS films and thus the photovoltaic performance of planar PSCs. The conductivity of PEDOT:PSS is significantly enhanced from 10⁻³ to 10¹ S cm⁻¹. The conductivity enhancement is not due to the solvent but mainly MAI. Even more significant conductivity enhancement occurs for PEDOT:PSS films after being coated with a dimethylformamide (DMF) solution of MAI, while pure DMF only slightly increases the conductivity of PEDOT:PSS by a factor of 2–3. PEDOT:PSS films become rougher after the deposition of a perovskite or MAI layer. The conductivity enhancements are attributed to the phase segregation of PSSH chains from PEDOT:PSS and the conformational change of PEDOT chains. The treatment of PEDOT:PSS with the organic solutions of MAI and solvents of perovskite precursor solutions also affects the photovoltaic performance of the planar PSCs.