Ionogel-perovskite matrix enabling highly efficient and stable flexible solar cells towards fully-R2R fabrication

Abstract

Flexible perovskite solar cells (PSCs) are one important candidate towards scalable and low-cost roll-to-roll (R2R) photovoltaics, having achieved over 22% efficiency in spin-coating-processed devices. However, the high requirements for flexibility, efficiency and stability in R2R-compatible fabrication seriously limit overall device performance. Elastic organic additives are always incorporated to recover the fatigue grain boundaries as a compromise stratagem between device flexibility and performance. In this work, a crosslinkable multi-functional ionogel (IG)-modified perovskite polycrystalline film was fabricated in situ using a R2R-compatible bar-coating-processed fabrication method. Engineering of the ionic liquids and polymer network effectively regulated both the mechanical properties and passivation effect of the perovskite devices. Our well-designed grain boundary exhibited ultra-high elongation, toughness and rapid room-temperature self-healing ability, benefiting from the dissipation-induced toughening and dynamic physical cross-linking sites. Additionally, the real-time space- and energy-level-dependent trap density showed significant suppression of intrinsic and bend-induced defects. As a result, a record efficiency of 21.76% with the lowest V_OC loss was achieved in flexible PSCs based on a scalable coating process, and unprecedented improvements in the operational stability (T₉₀ > 1336 h), mechanical stability (T₉₀ > 25 000 cycles, 5 mm) and water-resistant stability were also accomplished in the same flexible PSCs.