Tautomeric mixture coordination enables efficient lead-free perovskite LEDs.

Abstract

Lead halide perovskite light-emitting diodes (PeLEDs) have demonstrated remarkable optoelectronic performance1-3. However, there arepotential toxicity issues with lead4,5 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 thelead-free tinperovskiteTEA2SnI4 (TEAI is2-thiopheneethylammonium iodide) by incorporating cyanuric acid. We demonstrate that a crucial function of the coordination is to amplify theelectronic effects, even for those Sn atoms that aren't strongly bonded with cyanuric acidowing to the formation of hydrogen-bonded tautomeric dimer and trimer superstructures on the perovskite surface. This electron localization weakens adverse effects from Anderson localization and improves ordering in the crystal structure of TEA2SnI4. These factors result in a two-orders-of-magnitude reduction in thenon-radiative recombination capture coefficient and an approximately twofold enhancement inthe exciton binding energy. Our lead-free PeLED has an external quantum efficiency of up to 20.29%, representing a performance comparable to that of state-of-the-art lead-containing PeLEDs6-12. We anticipate that these findings will provide insights into the stabilization of Sn(II) perovskites and further the development of lead-free perovskite applications.