The role of halide oxidation in perovskite halide phase separation

Kerner, Ross A.; Xu, Zhaojian; Larson, Bryon W.; Rand, Barry P.

doi:10.1016/j.joule.2021.07.011

Cited by 109 publications

(138 citation statements)

References 92 publications

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“…Other techniques including luminescence mapping, combined with SEM have also aided the investigation of the phase separation process in terms of spatial distribution of the de-mixed phases [4d, 16]. Various reviews on this topic can be found in the literature [7,14,17].…”

Section: Photo De-mixing In Mixed Halide Perovskitesmentioning

confidence: 99%

“…Besides fundamental interest, this process has also been in the spotlight of application research as it has hindered the development of suitable, phase stable mixed halide perovskite thin films for use in optoelectronic devices [3]. Several studies have attempted to explain the experimental observations by invoking polaron formation and strain effects [4], bandgap reduction due to iodide rich phase formation [5] charge carrier trapping and concentration gradients from suface to bulk [6], halide oxidation and mass transport [7]. As the underlying process enabling photo de-mixing is the transport of ions occurring in the mixed halide perovskite, a detailed knowledge of the defect chemistry in these materials is important for addressing the questions on its origin [8].…”

Section: Introductionmentioning

confidence: 99%

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Photo de-mixing in mixed halide perovskites: the roles of ions and electrons

et al. 2022

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Mixed halide perovskites have attracted great interest for applications in solar cells, light emitting diodes and other optoelectronic devices due to their tunability of optical properties. However, these mixtures tend to undergo de-mixing into separate phases when exposed to light, which compromises their operational reliability in devices (photo de-mixing). Several models have been proposed to elucidate the origin of the photo de-mixing process, including the contribution of strain, electronic carrier stabilization due to composition dependent electronic energies, and light induced ionic defect formation. In this perspective we discuss these hypotheses and focus on the importance of investigating defect chemical and ion transport aspects in these systems. We discuss possible optoionic effects that can contribute to the driving force of de-mixing and should therefore be considered in the overall energy balance of the process. These effects include the selective self-trapping of photo-generated holes as well as scenarios involving multiple defects. This perspective provides new insights into the origin of photo de-mixing from a defect chemistry point of view, raising open questions and opportunities related to the phase behavior of mixed halide perovskites.

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Section: Photo De-mixing In Mixed Halide Perovskitesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photo de-mixing in mixed halide perovskites: the roles of ions and electrons

et al. 2022

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“…Despite the great achievements of the researchers made, such strategy arises concerns of inevitable phase separation, and potentially poses a risk of limiting device performance. [29,30] It is worth noting that straightly tailoring Sn ratio to 20% and 90% [31] without doping, the bandgap falls to the ideal value around 1.33 eV. Based on reducing Sn content substitution to optimize the device performance, 20% Sn exhibits more competitive.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Selective Targeting Anchor Strategy Affords Efficient and Stable Ideal‐Bandgap Perovskite Solar Cells

Liang

Zhang

et al. 2022

Advanced Materials

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Mixed lead–tin perovskite solar cells (LTPSCs) with an ideal bandgap are demonstrated as a promising candidate to reach higher power conversion efficiency (PCE) than their Pb‐counterparts. Herein, a Br‐free mixed lead–tin perovskite material, FA0.8MA0.2Pb0.8Sn0.2I3, with a bandgap of 1.33 eV, as a perovskite absorber, is selected. Through density functional theory calculations and optoelectronic techniques, it is demonstrated that both Pb‐ and Sn‐related A‐site vacancies are pushed into deeper energetic depth, causing severe nonradiative recombination. Hence, a selective targeting anchor strategy that employs phenethylammonium iodide and ethylenediamine diiodide as co‐modifiers to selectively anchor with Pb‐ and Sn‐related active sites and passivate bimetallic traps, respectively, is established. Furthermore, the selectivity of the molecular oriented anchor passivation is demonstrated through energetic depth specificity of Pb‐ and Sn‐related traps. As a result, a substantially enhanced open‐circuit voltage (VOC) from 0.79 to 0.90 V for the LTPSCs is achieved, yielding a champion PCE of 22.51%, which is the highest PCE among the reported ideal‐bandgap PSCs. The VOC loss is reduced to 0.43 V.

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“…Herein, we present DFT calculations for defects associated with the I − to I 0 transition (y ≥ x in FA 1+x PbI 3+y ) with a specific focus on the formed chemical species [42]…”

Section: Introductionmentioning

confidence: 99%

Charge Compensation by Iodine Covalent Bonding in Lead Iodide Perovskite Materials

Holland¹,

Rockett

Sanehira³

et al. 2022

Crystals

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Metal halide perovskite materials (MHPs) are a family of next-generation semiconductors that are enabling low-cost, high-performance solar cells and optoelectronic devices. The most-used halogen in MHPs, iodine, can supplement its octet by covalent bonding resulting in atomic charges intermediate to I− and I0. Here, we examine theoretically stabilized defects of iodine using density functional theory (DFT); defect formation enthalpies and iodine Bader charges which illustrate how MHPs adapt to stoichiometry changes. Experimentally, X-ray photoelectron spectroscopy (XPS) is used to identify perovskite defects and their relative binding energies, and validate the predicted chemical environments of iodine defects. Examining MHP samples with excess iodine compared with near stoichiometric samples, we discern additional spectral intensity in the I 3d5/2 XPS data arising from defects, and support the presence of iodine trimers. I 3d5/2 defect peak areas reveal a ratio of 2:1, matching the number of atoms at the ends and middle of the trimer, whereas their binding energies agree with calculated Bader charges. Results suggest the iodine trimer is the preferred structural motif for incorporation of excess iodine into the perovskite lattice. Understanding these easily formed photoactive defects and how to identify their presence is essential for stabilizing MHPs against photodecomposition.

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The role of halide oxidation in perovskite halide phase separation

Cited by 109 publications

References 92 publications

Photo de-mixing in mixed halide perovskites: the roles of ions and electrons

Photo de-mixing in mixed halide perovskites: the roles of ions and electrons

A Selective Targeting Anchor Strategy Affords Efficient and Stable Ideal‐Bandgap Perovskite Solar Cells

Charge Compensation by Iodine Covalent Bonding in Lead Iodide Perovskite Materials

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