Tautomeric mixture coordination enables efficient lead-free perovskite LEDs

Lead-free perovskite light-emitting diodes (LEDs) prepared using tautomeric mixture coordination provide improved ordering in the crystal structure, reduced recombination and enhanced exciton binding energy compared with lead-containing perovskite-based LEDs. Lead halide perovskite light-emitting diodes (PeLEDs) have demonstrated remarkable optoelectronic performance^ 1 – 3 . However, there are potential toxicity issues with lead^ 4 , 5 and removing lead from the best-performing PeLEDs—without compromising their high external quantum efficiencies—remains a challenge. Here we report a tautomeric-mixture-coordination-induced electron localization strategy to stabilize the lead-free tin perovskite TEA_2SnI_4 (TEAI is 2-thiopheneethylammonium iodide) by incorporating cyanuric acid. We demonstrate that a crucial function of the coordination is to amplify the electronic effects, even for those Sn atoms that aren’t strongly bonded with cyanuric acid…