Improved Performance of Perovskite Solar Cells by Suppressing the Energy-Level Shift of the PEDOT:PSS Hole Transport Layer

In inverted architectures of perovskite solar cells (PSCs), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been widely used as the hole transport layer (HTL). An issue occurring in such PSCs is that the hole transport level of PEDOT:PSS shifts upward since methylammonium iodide (MAI) used for the perovskite structure organization interacts with the underlying PEDOT:PSS HTL as a reducing agent, which impedes hole extraction and therefore lowers the performance of PSCs. To overcome this issue, we demonstrate a way of adding tetraethoxysilane (TEOS) into a water-based PEDOT:PSS solution. The HTL spin-coated from the solution contains PEDOT:PSS, which is blended with siloxanes because the polymerization of TEOS takes place via the hydrolysis reaction. This siloxane blending suppresses the MAI-induced reducing reaction and upward energy-level shift of PEDOT:PSS. Using the siloxane-blended PEDOT:PSS HTL in PSCs leads a ∼1.3-fold increase in power conversion efficiencies of iodide-based PSCs from the original ∼10.58% to ∼13.65%.