Abstract
The all-inorganic nature of CsPbI 3 perovskites offers an avenue to enhance stability in perovskite devices. Concerted research efforts have led to improved stability of the black phase in CsPbI 3 films; however, these strategies – including strain and doping – are based on organic-ligand-capped perovskites, which prevent perovskites from forming the close-packed QD solids necessary to achieve high charge transport and thermal transport. Here we develop an inorganic ligand exchange that leads to CsPbI 3 QD films that unite superior phase stability with increased thermal transport. We demonstrate that the atomic ligand exchanged QD films, once mechanically coupled, exhibit improved phase stability, and we link this to distributing strain across the film. Further, operando measurements of the temperature of LEDs indicate that KI-exchanged QD films exhibit increased thermal transport compared to controls that rely on organic ligands. The LEDs exhibit a maximum EQE of 23% with EL emission centered at 640 nm (FWHM of ~31 nm). These red LEDs provide an operating half lifetime of 10 hours (luminance of 200 cd/m 2 ), an operating stability that is 6x higher than that of control devices.
This work was supported by the Ontario Research Fund Research-Excellence Program and the Natural Sciences and Engineering Research Council of Canada (NSERC grant number 216956-12). M.I.S. acknowledges the support of Banting Postdoctoral Fellowship Program administered by the Government of Canada. We acknowledge financial support from Natural Science Foundation of China (Nos. 51821002, 91733301) and the Collaborative Innovation Center of Suzhou Nano Science and Technology. Y.K. Wang acknowledges the financial support of the China Scholarship Council (No. 201806920067). Z.H.L acknowledges the financial support of the National Natural Science Foundation of China (grant number 11774304)