Dendritic CsSnI₃ for Efficient and Flexible Near‐Infrared Perovskite Light‐Emitting Diodes

Abstract

All‐inorganic and lead‐free CsSnI3 is emerging as one of the most promising candidates for near‐infrared perovskite light‐emitting diodes (NIR Pero‐LEDs), which find practical applications including facial recognition, biomedical apparatus, night vision camera, and Light Fidelity. However, in the CsSnI3‐based Pero‐LEDs, the holes injection is significantly higher than that of electrons, resulting in unbalanced charge injection, undesired exciton dissipation, and poor device performance. Herein, it is proposed to manage charge injection and recombination behavior by tuning the interface area of perovskite and charge‐transporter. A dendritic CsSnI3 structure is prepared on the hole‐transporter, only making a bottom contact with the hole‐transporter and exposing all other available crystal surfaces to the electron‐transporter. In other words, the interface area of perovskite/electron‐transporter is significantly higher than that of perovskite/hole‐transporter. Moreover, the embedding interface of perovskite/electron‐transporter can spatially confine holes and electrons, increasing the radiation recombination. By taking advantage of the dendritic structure, efficient lead‐free NIR Pero‐LEDs are achieved with a record external quantum efficiency (EQE) of 5.4%. More importantly, the dendritic structure shows great superiorities in flexible devices, for there is almost no morphology change after 2000‐cycles of bends, and the fabricated Pero‐LEDs can keep 93.4% of initial EQEs after 50‐cycles of bends.

Tin-based halide perovskite materials: properties and applications

“…2020 red standard of (0.708, 0.292). 146 In another work, Lu et al 147 reported the flexible near-infrared tin-based CsSnI 3 PeLED. A dendritic CsSnI 3 perovskite structure was sandwiched between PEDOT:PSS and B3PyMPM as the hole and electron transport layers.…”

Environment‐Friendly Perovskite Light‐Emitting Diodes: Progress and Perspective

“…More importantly, the fabricated PeLEDs can also keep 93.4% of initial EQEs after 50‐cycle bends. [ 115 ] Thus, other environment‐friendly perovskites are also possible to form structures suitable for flexible application via readily controlling the concentrations of the precursor.…”

“…Lu et al successfully prepared the high-quality CsSnI 3 perovskite films with dendritic structure, which remained as fresh after 2000-cycle bends. More importantly, the fabricated PeLEDs can also keep 93.4% of initial EQEs after 50-cycle bends [115]. Thus, other environment-friendly perovskites are also possible to form structures suitable for flexible application via readily controlling the concentrations of the precursor.…”

Wavelength-Tuneable Near-Infrared Luminescence in Mixed Tin–Lead Halide Perovskites

“…They found unbalanced charge injection, that the hole injection is higher than that of electron, was a cause of poor device performance. The dendritic structure remedied this by increasing electron injection, and the CsSnI 3 -based perovskite LEDs based on this structure obtained a record EQE of 5.4% with an acceptable efficiency roll-off and a high radiance of 162 W sr −1 m −2 ( Lu et al, 2021 ). However, the efficiency of Sn-based NIR-LEDs remains considerably lower than that of Pb-based devices owing to the rapid oxidation of Sn 2+ to Sn 4+ , which leads to poor device performance and accelerates degradation.…”