Tunable deep-blue luminescence from ball-milled chlorine-rich Cs_x(NH₄)_1−xPbCl₂Br nanocrystals by ammonium modulation

Abstract

The progress of deep-blue perovskite light-emitting diodes (DB-PeLEDs) lags far behind their green and red counterparts due to the lack of stable DB perovskite materials. Here, a novel class of...

Deciphering the roles of ammonium doping for lead-free (NH4)xCs3−xCu2I5 perovskites to regulate the photoelectronic properties

“…35 A similar role of defect passivation was also proved for NH 4 + -doped CsPbCl 2 Br perovskites by our group. 20 Based on our XRD, XPS and FTIR results, we suggest that the appropriate substitution of Cs + cations by NH 4 + may inhibit Cs-related defects like Cs vacancies, strengthen the Cu–I framework, 12 and thus reduce the generation of the non-radiative recombination process. The PL intensity reaches the optimal value at dose x = 0.9 because increased non-radiative process can occur when excessive doping of NH 4 + starts to produce additional XRD impurity phases.…”

“…Compared to organic amine cations, NH 4 + is undersized and symmetrized, which makes it much easier to interact with and to insert into Pb–I frameworks than larger organic cations and may result in suppressed ion migration and defects. 19–21 Currently, little attention is being paid to the study of NH 4 + -based perovskites. The recently reported NH 4 I-intermediated MAPbI 3 and CsPbI 3 crystallization could achieve high quality materials but no NH 4 + component remained after the processing.…”

“…The recently reported NH 4 I-intermediated MAPbI 3 and CsPbI 3 crystallization could achieve high quality materials but no NH 4 + component remained after the processing. 21,22 Pioneering breakthroughs on NH 4 + -doped Pb-based perovskites, such as (NH 4 ) 0.5 Cs 0.5 Pb(I 0.5 Br 0.5 ) 3 , 21 MA 1− x (NH 4 ) x PbBr 3 23 and Cs x (NH 4 ) 1− x PbCl 2 Br, 20 were made very recently in order to improve the luminescence properties, suggesting NH 4 + can effectively passivate defects and stabilize the materials. There has been no relevant report on NH 4 + -doped Cu-based perovskites so far, wherein we boldly suppose that NH 4 + will also serve a positive function.…”

“…The same phenomena were observed in previous reports on Pb-based perovskites. 20–22 Si et al proposed that NH 4 + with a smaller ionic radius (146 pm) can preferentially diffuse into the [PbI 6 ] 4− octahedral framework than MA + (180 pm), resulting in heterogeneous nucleation sites and an enlarged grain size. 22 Normally, the grain boundaries act as nonradiative recombination sites to weaken the photoelectrical properties.…”

“…The short decay time ( τ 1 ) and long decay time ( τ 2 ) correspond to the non-radiative and radiative recombination processes, 17,26 respectively, with different weighted amplitudes ( α ) in Table S3 (ESI†). The prolonged τ ave and τ 1 suggest that the doping of NH 4 + imposes a positive influence on the radiative recombination of metal halide perovskites while suppressing the nonradiative path, 20 which can explain the higher PLQY of NH 4 + -doped Cs 3 Cu 2 I 5 .…”