Controlling the Phase Segregation in Mixed Halide Perovskites through Nanocrystal Size

Abstract

Mixed halide perovskites are one of the promising candidates in developing solar cells and light-emitting diodes (LEDs), among other applications, because of their tunable optical properties. Nonetheless, photoinduced phase segregation, by formation of segregated Br-rich and I-rich domains, limits the overall applicability. We tracked the phase segregation with increasing crystalline size of CsPbBr3–xIx and their photoluminescence under continuous-wave laser irradiation (405 nm, 10 mW cm–2) and observed the occurrence of the phase segregation from the threshold size of 46 ± 7 nm. These results have an outstanding agreement with the diffusion length (45.8 nm) calculated also experimentally from the emission lifetime and segregation rates. Furthermore, through Kelvin probe force microscopy, we confirmed the correlation between the phase segregation and the reversible halide ion migration among grain centers and boundaries. These results open a way to achieve segregation-free mixed halide perovskites and improve their performances in optoelectronic devices.

Photoinduced Anion Segregation in Mixed Halide Perovskites

“…Gualdrón-Reyes and colleagues [59] corroborate these results. In their study, (x = 0.11, 0.52, and 0.79) CsPb(I 1-x Br x ) 3 films with average grain sizes below~45 nm exhibit suppressed halide segregation under CW illumination (λ exc = 405 nm; I exc = 10 mW cm -2 ).…”

Influence of bromide content on iodide migration in inverted MAPb(I1−xBrx)3perovskite solar cells

“…† In Fig. S3a † the increase in V oc as a function of bromide content is related with the change in the bandgap, [16][17][18]36,49 as shown in Fig. S4 and Table S1.…”

“…47 It has also been reported that as the amount of bromide is increased, phase segregation can occur, particularly when the lm is under illumination. 16,40,41 Phase separation causes the 28.8 peak to split into two peaks, associated with iodide and bromide rich regions. 40,41 No phase separation was observed in these samples, although these lms were not exposed to light before the XRD spectrum was measured.…”

“…8,9 Due to the ionic nature of the components, perovskite materials are fairly easy to synthesize via solution-based methods [10][11][12][13] and at the same time, the performance of PSC has proven to be very resilient to defects. 14,15 It is also possible to change the chemical composition of the lead halide perovskites to effectively and systematically tune their bandgap, [16][17][18] making them particularly attractive for a wide variety of applications including light emitting diodes 16,19,20 and tandem solar cells. 21,22 However, in spite of these promising features, the development of perovskite solar cells still presents important challenges: low stability, particularly under high humidity conditions, [23][24][25] and a hysteretic behavior that appears to be intrinsic to lead halide perovskite devices.…”

A Hybrid Artificial Photocatalysis System Splits Atmospheric Water for Simultaneous Dehumidification and Power Generation

“…In addition, the (100)/(111) Cu 2 O was characterized by Kelvin probe force microscopy (KPFM) at ambient condition to determine the surface potential on the exposed (100) and (111) planes. For a semiconductor, the surface potential is always related to the surface energy of a material, which differs from the bulk work function ascribed to the formed space charge region near the interface . Therefore, surface potential mainly reflects the properties of a thin surface layer, such as surface work function and Fermi level.…”