Trimethylsilyl Iodine-Mediated Synthesis of Highly Bright Red-Emitting CsPbI3 Perovskite Quantum Dots with Significantly Improved Stability

Herein, we report highly bright and stable CsPbI3 (CPI) perovskite quantum dots (PQDs) synthesized with trimethylsilyl iodine (TMSI) under a reaction circumstance with the I/Pb molar ratio of similar to 4.2. The obtained CPI (TMSI-CPI) PQDs show near-unity photoluminescence quantum yields (PLQYs) in solution and high stability (only 9% loss in PLQY after 105 day storage) under ambient and dark conditions. The thermal stability of TMSI-CPI PQDs is also improved: the degradation temperature is higher than that of traditional hot-injection-synthesized CPI (Tra-CPI) PQDs. X-ray photoelectron spectroscopy results show that the TMSI-CPI PQDs have a highly iodine-rich surface (the I/Pb atomic ratio is up to 4.4), which is believed to be responsible for such high stability and PLQYs. Further, the size and surface properties of CPI PQDs can be easily adjusted by changing the amount of TMSI. Finally, we fabricated QDs-based light-emitting diodes (QLEDs) utilizing TMSI-CPI PQDs as an emissive layer showing a maximum luminance of 365 cd m(-2) and external quantum efficiency of 1.8%. During a working period of 2 h, no shift and broadening of the electroluminescence spectra happen for TMSI-CPI-based QLEDs with an initial luminance of 100 cd m(-2); the device lifetime for which the luminance drops to half of its initial value (100 cd m(-2)) reaches 3.11 h, which is nearly 7 times longer than that of Tra-CPI-based QLEDs.