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

Abstract

Despite their low band gap, the utility of CsPbI 3 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 CsPbI 3 NCs can be obtained by tweaking the conventional hot-injection method employing NH 4 I 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 CsPbI 3 NCs are shown to be the result of NH 4 + replacing some surface Cs + of an iodide-rich surface of the NCs. These phase-stable and highly luminescent CsPbI 3 NCs with significantly suppressed PL blinking can be useful single-photon emitters and promising materials for optoelectronic and solar photovoltaic applications.

Facet Engineering for Decelerated Carrier Cooling in Polyhedral Perovskite Nanocrystals

“…The past few years have witnessed the great promise of six-faceted ({110}, {002}) all-inorganic perovskite NCs (CsPbX 3 ; X = Br, Cl, I) in photovoltaic and optoelectronic applications. − Their unique optical properties, such as near-unity photoluminescence quantum yields (PLQYs), narrow emission spectra, tunable photoluminescence (PL) in the visible region, long carrier diffusion length, etc., are keys to their massive success in several real applications such as displays, lasers, LEDs and solar cells. − Despite the vast accomplishments, six-faceted cube NCs are not free from challenges; in fact, many of them are directly linked to the device’s performance. − One such example is the rapid cooling (∼0.5–0.7 ps) of hot carriers (HCs) in cubic nanocrystals (NCs), a significant setback toward achieving a power conversion efficiency (PCE) of a theoretically predicted value (∼66%) or at least to a Shockley–Queisser limiting value (∼33%). , Extensive efforts have been put forward in slowing down the cooling in perovskite materials to a time scale slower than the time needed for the extractions of HCs. Such attempts proposed several phenomena, including acoustical–optical phonon upconversion, hot-phonon bottleneck, large-polaron formation, Auger heating, etc., were responsible for slow cooling in perovskite materials. , For instance, Fu et al and Wang et al have observed decelerated cooling in perovskite materials exploiting the Auger heating and synergetic effect of doped alkali cations (K + , Cs + , Rb + ) reducing the phonon bottleneck threshold.…”

Cubic CsPbI3 Nanoarchitectonics with High and Stable Photoluminescence toward White Light-Emitting Diodes

“…The peaks at 2854 and 2920 cm –1 are attributed to the stretching vibration of CH 2 and CH 3 in OA and OAm, respectively. The characteristic peak at 1465 cm –1 originates from the in-plane bending oscillation of OAm and OA ligands . However, the characteristic peaks at 1095 and 1260 cm –1 were only observed in SDBS-CsPbI 3 NCs, corresponding to S–O and SO, respectively .…”

“…Both samples were indexed as the and OA ligands. 31 However, the characteristic peaks at 1095 and 1260 cm −1 were only observed in SDBS-CsPbI 3 NCs, corresponding to S−O and S�O, respectively. 44 This result confirmed the presence of SDBS ligands on the surface of CsPbI 3 NCs.…”

“…In addition, I ion vacancies outside nanocrystals have recently been proven to be the main source of defects, 18,30 after synthesis. 31 To date, many teams have prepared highperformance CsPbI 3 NCs using ligands with strong binding forces such as TOP, but the preparation process is complex and difficult for practical application. 32−35 The key to solving the above problems is by eliminating I vacancies on the surface as much as possible and reducing the loss of surface ligands.…”

“…Capping ligands can block the external environment to provide strong spatial effects for NCs. In addition, I ion vacancies outside nanocrystals have recently been proven to be the main source of defects, , and nearly uniform PLQYs can be achieved by adding additional iodide after synthesis . To date, many teams have prepared high-performance CsPbI 3 NCs using ligands with strong binding forces such as TOP, but the preparation process is complex and difficult for practical application. − …”