High-Brightness Perovskite Light-Emitting Diodes with Suppressed Efficiency Roll-off Using the Green Solvent γ-Valerolactone

The application of promising perovskite light-emitting diodes (PeLEDs) faces a significant challenge known as efficiency roll-off, which refers to the decline in external quantum efficiency (EQE) at high current densities. This issue arises mainly from high trap densities in perovskite films and imbalanced carrier injection, which limit improvements in brightness and stability of PeLEDs. Here, we develop a green solvent strategy using γ-valerolactone (GVL) to suppress efficiency roll-off in PeLEDs. This strategy effectively slows down the crystallization kinetics, yielding cubic-phase formamidinium lead triiodide (α-FAPbI₃) films with reduced trap states, enhanced charge carrier injection, and suppressed Auger recombination. As a result, we achieve a record radiance of 1411 W sr^-1 m^-2 for GVL-based PeLEDs. These PeLEDs exhibit a substantially reduced efficiency roll-off, maintaining an EQE above 20% even at a high current density of 900 mA cm^-2. Our findings highlight the potential of the green solvent approach for developing high-brightness, high-efficiency PeLEDs for practical applications.