Understanding and Quantifying Ion Diffusion in Two-Dimensional Halide Perovskite Heterostructures

Halide perovskites are exciting new semiconductors that show great promising in low cost and high-performance optoelectronics devices including solar cells, LEDs, photodetectors, lasers, etc. However, the poor stability, particularly ion migration, is limiting their practical use. In this talk, I will present our recent efforts in the synthesis and fabrication of lateral and vertical 2D perovskite epitaxial heterostructures and the use of these heterostructures as diffusion couples to quantitatively understand the ion diffusion and migration behaviors. Ion diffusion and migration were induced via heat, light, and bias; and the diffusion and migration were visualized via advanced photoluminescence and X-ray fluorescence mapping techniques. Through introduction of pi-conjugated bulky organic cations, enhanced stability and suppressed ion migration were observed. These findings provide important fundamental insights into the immobilization of ionic species and stabilization of halide perovskite semiconductors and demonstrate a materials platform for complex and molecularly thin superlattices, devices and integrated circuits.