Controlling Crystallization and Carrier Recombination for Efficient Tin Perovskite Light-Emitting Diodes

Tin-based perovskite light-emitting diodes (PeLEDs) have attracted extensive attention because of their environmental friendliness and solution processability. However, tin perovskite films usually suffer from easy oxidation of Sn²⁺ and uncontrollable crystallization, which result in undesirable film quality and device performance. Herein, different from the widely used organic additives in tin PeLEDs, we introduced an inorganic additive, potassium thiocyanate (KSCN), into the tin perovskite precursor solution. A comparative study with KI additive reveals that K⁺ can effectively regulate the crystallization process and improve the film morphology, while the strong coordination interaction between SCN^– and Sn²⁺ can inhibit the oxidation of Sn²⁺ and further passivate the defects. Benefiting from the synergy of K⁺ and SCN^–, the quality of tin perovskite films is significantly improved, enabling enhanced radiative recombination and suppressed nonradiative recombination. As a result, the maximum EQE of the near-infrared (NIR) tin PeLEDs with KSCN modification dramatically increases from 6.57% to 10.17%, accompanied by notably improved operational stability. This work provides a robust inorganic additive strategy for optimizing the quality of tin perovskites toward high-performance tin PeLEDs.