Highly Efficient Inverted Perovskite Solar Cells With Sulfonated Lignin Doped PEDOT as Hole Extract Layer

Sulfonated-acetone-formaldehyde (SAF) was grafted with alkali lignin (AL) to prepare grafted sulfonated-acetone-formaldehyde lignin (GSL). Considering the rich phenolic hydroxyl groups in GSL, we detected a hole mobility of 2.27 × 10–6 cm2 V–1 s–1 with GSL as a hole transport material by space-charge-limited current model. Compared with nonconjugated poly(styrene sulfonic acid), GSL was applied as p-type semiconductive dopant for PEDOT to prepare water-dispersed PEDOT:GSL. PEDOT:GSL shows enhanced conductivity compared with that of PEDOT:PSS. Simultaneously, the enhanced open-circuit voltage, short-circuit current density, and fill factor are achieved using PEDOT:GSL as a hole extract layer (HEL) in sandwich-structure inverted perovskite solar cells. The power conversion efficiency is increased to 14.94% compared with 12.6% of PEDOT:PSS-based devices. Our results show that amorphous GSL is a good candidate as dopant of PEDOT, and we provide a novel prospective for the design of HEL based on lignin, a renewable biomass and phenol derivatives.