Co-Doping of Cerium and Bismuth into Lead-Free Double Perovskite Cs₂AgInCl₆ Nanocrystals Results in Improved Photoluminescence Efficiency

Abstract

Lead-free double cation metal halide perovskites have recently attracted considerable attention, with continuing research efforts focusing on the improvement of their stability and photoluminescence quantum yield (PL QY). In this study, Ce3+ has been co-doped together with Bi3+ into lead-free double perovskite Cs2AgInCl6 nanocrystals (NCs) in order to improve their crystallinity and PL QY. Both uncoordinated chloride ions and silver vacancies could be eliminated using this co-doping strategy, and the resulting Ce3+,Bi3+-co-doped Cs2AgInCl6 NCs showed adjustable PL emission peaks in the range of 589 to 577 nm by varying the doping amount of Ce3+ with a fixed feeding ratio of bismuth precursor set at 1%. Cs2AgInCl6 NCs doped with 1% Bi alone reached a PL QY of 10% for the PL peak centered at 591 nm, while those co-doped with 1% Bi and 2% Ce together achieved the highest PL QY of 26% for the PL peak centered at 580 nm. The use of Ce3+ as a dopant promoted the localization of self-trapped excitons to prevent PL quenching, although the ion’s 5d excited state may potentially provide an energetically favorable indirect route for the radiative relaxation process. This also resulted in a blue shift of the PL maximum and increased the exciton binding energy, thus promoting the radiative recombination of self-trapped excitons.

Hot-Injection Synthesis Protocol for Green-Emitting Cesium Lead Bromide Perovskite Nanocrystals

“…While based on the hot-injection procedure, multiple efforts have been made throughout the following years to enhance the stability and boost the PL QY of perovskite NCs. Doping/alloying to inhibit the nonradiative pathways, − surface treatments for effective passivation of defects, − proper choice of ligands, and dimensionality engineering have all been applied. − Besides, strategies are appearing now aimed at reducing or eliminating the amount of lead in perovskite NCs through its partial or complete substitution, − which led to the development of A 2 M + M 3+ X 6 lead-free double perovskites. − …”

Antimony and bismuth cooperation to enhance the broad yellow photoluminescence of zero-dimensional hybrid halide

“…[18][19][20][21][22] However, the effect of bismuth dopants on In-based halide perovskites (represented by Cs 2 AgInCl 6 perovskites) has been extensively studied in the field of all-inorganic perovskites. In these studies, by adjusting the optical bandgap, 23 breaking the parity forbidden transition, 24 promoting light absorption and introducing an energy transmission channel, [25][26][27] Bi 3+ has been shown to play a role in photoluminescence (PL), which is different from the luminescent center Sb 3+ . Shi et al recently reported that when Sb 3+ and Bi 3+ ions were co-doped into the Cs 2 NaInCl 6 double perovskite, the Bi 3+ dopants induced [SbCl 6 ] 3À octahedral subbands and enhanced the broadband yellow radiation of selftrapped excitons (STEs) in the [SbCl 6 ] 3À octahedra.…”

Light Emission from Low‐Dimensional Pb‐Free Perovskite‐Related Metal Halide Nanocrystals

“…Furthermore, in these low-D NCs, apart from a few examples, [129] doping strategies have not been yet fully exploited. For example, the co-doping with two metal cations for tunable light emission, which has been successfully exploited in both 3D CsPbX 3 [130] and double perovskite NCs, [131] has been demonstrated only in Cs 2 ZrCl 6 microcrystals, but not in NCs. [132,133] Therefore we believe that an interesting research direction will be the development of effective doping strategies of low-D NCs.…”