Looking at a range of different compositions with varying ratios of bromine to iodine, we are able to observe the kinetics of photo-induced unmixing of mixed-halide perovskites and the formation of multiple distinct crystalline phases. Utilizing grazing-incidence wide angle x-ray scattering (GIWAXS), we have observed in situ reversible structural changes that occur over time scales of 30 minutes to an hour in mixed-halide methylammonium perovskite thin films as a result of light soaking at approximately 1 sun intensity. Structural changes that result in optical changes may come from halide migration and subsequent segregation in the perovskite. While the impacts of photo-induced segregation on optical properties have been well documented, the underlying impacts on perovskite structure remain less clear. While mixed-halide perovskites are ideal for use in tandem solar cells due to their tunable band gap, they are limited by reversible photo-induced degradation. We perform structural, magnetic, optical and magneto-optical temperature-dependent measurements to verify a successful magnetic doping of the perovskite and to show how photoluminescence and magnetization properties relate. We investigate how localized excitons couple with the magnetic moments of the introduced impurities by detecting a dependence of the emitted lights polarization on the magnetization. We investigated the influence of both halides and magnetic impurities on the long-range magnetic ordering of the materials with respect to the structural and optical properties. We produced a selection of magnetic perovskites using simple solution processing techniques by doping of the host material, Ruddlesden-Popper hybrid perovskite ((PEA) 2PbX 4 with X = Cl, Br, I), with different magnetic ions like Mn 2+, Fe 2+, Co 2+, Ni 2+ and Eu 2+. Due to their outstanding optoelectronic properties and high defect tolerance, organo-metal halide perovskites form an ideal system for efficient magnetic doping. The material class of DMS is obtained by introducing a substantial number of magnetic ions to an otherwise non-magnetic host semiconductor. Fully inorganic dilute magnetic semiconductors (DMS) have been known for decades, which show diverse functionalities like control of magnetism by electrical fields. Most importantly, such codoped NCs with multiple emission channels hold a high potential to be applied in a wide range of applications, including multiplexed biological labelling and sensing, multi-channel photodetectors, stimuli-responsive inks for coding, encryption and decryption, and photon management devices in the future.Ĭombining the advantageous electrical and optical properties of semiconductors with magnetic characteristics gives access to extraordinary phenomena and applications. Therefore, co-doping both Mn 2+ and Yb 3+ ions into perovskite NCs can serve as a unique model system for studies of host-to-dopant and inter-dopant energy transfer mechanisms, as well as associated radiative and non-radiative decay pathways at each step. Owing to the high PL QYs and minimal reabsorption loss, the codoped perovskite NCs are demonstrated to be used as efficient emitters in luminescent solar concentrators, with greatly enhanced external optical efficiency compared to that of using solely Mn 2+ doped CsPbCl 3 NCs. Mechanism studies reveal different natures of emission mechanisms can be involved in a single batch of Mn 2+/Yb 3+ codoped perovskite NCs: (i) electronic inter-band transition (BG-PL) (ii) electronic transition of ion centers within local molecular complexes (Mn-PL) and (iii) defect-induced energy transfer and subsequent quantum cutting scheme (Yb-PL). By optimizing the dopant concentrations, the total photoluminescence quantum yield (PL QY) of the codoped NCs can reach up to ~125.3% due to quantum cutting effects. Owing to the completely separated energy relaxation channels among the intrinsic bandgap (BG), Mn 2+ and Yb 3+ dopant emissions, the obtained Mn 2+/Yb 3+ codoped CsPbCl 3 perovskite NCs exhibit a unique triple-wavelength emission profile simultaneously covering UV/blue (BG-PL), visible (Mn-PL) and NIR (Yb-PL) spectral regions. Here, a facile synthesis of Mn 2+/Yb 3+ codoped CsPbCl 3 NCs through a hot-injection technique is firstly reported. Current studies focus mostly on doping a single type of metal ions into the host perovskite NCs, while few research efforts have been made on simultaneous doping more than one type of metal ions into the same perovskite hosts and to study their synergic effects with intra-particle energy transfer processes. Doping metal ions into lead halide perovskite nanocrystals (NCs) has attracted great attention over the past few years due to the emergence of novel properties relevant to optoelectronic applications.
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