Ion-Exchange Polymer Network Enhanced Interfacial Compatibility for Stable and Efficient Inverted Perovskite Solar Cells.

ABSTRACT

Poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (PEDOTPSS) as a low-cost and water-processable hole transport material has been widely used in various optoelectronic devices. Although the incorporation of anionic polyelectrolyte PSS in PEDOT contributes to superior water solubility, the trade-off between efficiency and stability remains a challenging issue, limiting its reliable application in perovskite solar cells (PSCs). Herein, we proposed an ion-exchange (IE) strategy to effectively control the doping degree, interfacial charge dynamics, and reliability of PEDOTPSS in PSCs. This IE approach based on hard cation-soft anion rules enabled effective anion exchange between PEDOTPSS and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), which favored enhancing the film conductivity, regulating the perovskite crystallization, and reducing the carrier losses at the interfaces. Consequently, a notable increase of the open-circuit voltage from 0.88 to 1.02 V was realized, resulting in a champion efficiency of 18.7% compared to the control (15.4%) in inverted PSCs. More encouragingly, this IE strategy significantly promoted the thermal and environmental stability of unsealed devices by maintaining over 80% of initial efficiencies after 2000 h. This work provides an effective way to regulate the doping state of the PEDOT-based hole transport material and guides the development of robust polymeric conducting materials for efficient perovskite photovoltaics.