Phase-Stable and Highly Luminescent CsPbI₃ Perovskite Nanocrystals with Suppressed Photoluminescence Blinking

Despite their low band gap, the utility of CsPbI₃ nanocrystals (NCs) in solar photovoltaic and optoelectronic applications is rather limited because of their phase instability and photoluminescence (PL) intermittency. Herein we show that phase-pure, monodispersed, stable and highly luminescent CsPbI₃ NCs can be obtained by tweaking the conventional hot-injection method employing NH₄I as an additional precursor. Single-particle studies show a significant suppression of PL blinking. Among all NCs studied, 60% exhibit only high-intensity ON states with a narrow distribution of intensity. The remaining 40% of NCs exhibit a much wider distribution of PL intensity with a significant contribution of low-intensity OFF states. Excellent characteristics of these CsPbI₃ NCs are shown to be the result of NH₄⁺ replacing some surface Cs⁺ of an iodide-rich surface of the NCs. These phase-stable and highly luminescent CsPbI₃ NCs with significantly suppressed PL blinking can be useful single-photon emitters and promising materials for optoelectronic and solar photovoltaic applications.