Optimizing PEDOT:PSS with a Sodium Lignosulfonate Additive to Improve the Performance of Inverted Perovskite Solar Cells

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is considered to be a highly desirable hole transport material for inverted perovskite solar cells (PSCs) because of its low cost, simple preparation process, and high light transmittance. Unfortunately, its inherent drawbacks, such as suboptimal electrical conductivity and high interfacial defect density, hamper charge extraction efficiency and ultimately limit device performance. In this work, we incorporated an environmentally friendly additive, sodium lignosulfonate (LS), into PEDOT:PSS to enhance the photovoltaic performance of inverted PSCs. The optimized device with a 0.1 mg/mL LS-doped hole transport layer (HTL) displayed a significant increase in power conversion efficiency from 15.36% of the reference device (with pristine PEDOT:PSS HTL) to 17.28%. LS doping did not influence the morphology of the PEDOT:PSS film and the overlying perovskite film. Instead, it serves a dual function: improving conductivity to enhance hole extraction ability and reducing interface defects to decrease nonradiative recombination losses. Therefore, this work presents a straightforward and efficient additive engineering strategy to enhance the electrical performance of inverted PSCs.