Interface Engineering of a Compatible PEDOT Derivative Bilayer for High‐Performance Inverted Perovskite Solar Cells

Interface engineering is an important aspect for the improvement of perovskite solar cells (PVSCs). The hole transport layer with good interface contact, transport capability, and matched energy level is indispensable and critical for high‐performance photovoltaic devices. Herein, anode interface engineering with an excellent compatible bilayer of poly(3,4‐ethylene dioxythiophene):poly(styrenesulfo‐nate)/poly(3,4‐ethylene dioxythiophene) (PEDOT:PSS/PEDOT) doped with grafted sulfonated‐acetone–formaldehyde lignin (PEDOT:GSL) via a low‐temperature and water‐soluble process is presented. As a water‐processable interface material, PEDOT:GSL exhibits higher conductivity, as well as better structural and electronic homogeneities compared with PEDTO:PSS. Consequently, the PEDOT:PSS/PEDOT:GSL bilayer with tuned energy level, optical properties, and the combination of the trap passivation of GSL at the anode/perovskite interface can greatly improve charge extraction ability and reduce the interface recombination. Simultaneously, the homogeneous perovskite film is fabricated through optimizing the annealing process. The device with the power conversion efficiency up to 17.80% is achieved, with 32.6% improvement compared to PEDOT:PSS‐only device (13.42%). Our success to achieve high‐performance inverted PVSCs provides new understanding of PEDOT:PSS, and also new guidelines for anode interface engineering to further advancement of PVSCs. This promising approach paves the way to realize solution processable highly efficient PVSCs for potential practical applications.