High‐Pressure Band‐Gap Engineering in Lead‐Free Cs<sub>2</sub>AgBiBr<sub>6</sub> Double Perovskite

Li, Qian; Wang, Yonggang; Pan, Weicheng; Yang, Wenge; Zou, Bo; Tang, Jiang; Quan, Zewei

doi:10.1002/anie.201708684

Cited by 210 publications

(176 citation statements)

References 33 publications

(12 reference statements)

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“…[62,138] Zhou et al obtained an indirect bandgap of 2.52 eV for Cs 2 Ag-BiBr 6 NCs. [140] Specifically, Cs 2 AgBiBr 6 presented a bandgap of 1.7 eV at ≈15 GPa, which is comparable with that of MAPbI 3 . The enlarged bandgap can be ascribed to the quantum confinement effect in Cs 2 AgBiBr 6 NCs.…”

Section: + /Bi 3+ Halide Double Perovskitesmentioning

confidence: 76%

Progress of Lead‐Free Halide Double Perovskites

Igbari

Wang

Liao

2019

Advanced Energy Materials

343

297

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Although impressive performance has been obtained, PSCs are still far from commercial or real-life availability due to serious issues such as toxicity [15,16] and poor stability to heat, [17] oxygen, [18] moisture, [19,20] electric field, [21] and light. [18,22] The toxic nature of hybrid organic-inorganic lead halide perovskites has been traced to the presence of Pb in its chemical composition. [15,16,[23][24][25] Pb 2+ readily dissolves in water (e.g., rain water) to form a toxic solution capable of causing serious environmental pollution, harmful to human beings and the ecosystem. Besides their sensitivity to moisture, oxygen, light, electric field, or thermal stress, an existing self-degradation pathway [26,27] is also a big issue in hybrid organic-inorganic lead halide perovskites. Mixed-halide and mixed-cation perovskites have been investigated to address these issues. [28][29][30][31][32] The group IV elements, tin (Sn) [23,[33][34][35] and germanium (Ge), [34,36] have been employed as the replacements for Pb. However, the device performance through this approach has fallen short of the Pb-based ones. For example, the PCEs reported for Sn-based perovskite solar cells are usually less than 10%. [23,[33][34][35][37][38][39][40] In addition, the easy oxidation of Sn and Ge from the +2 state to the +4 state due to their high energy 5s and 4s orbitals makes them less promising for application in stable and long-term PSCs. [41] High throughput calculations also demonstrate that these substitutions are likely to compromise the ideal optoelectronic properties of MAPbI 3 . [42,43] Furthermore, low dimensional (e.g., 2D, 1D, and 0D) perovskites have also been used to address the stability issues in PSCs. [44][45][46][47][48] Recently, a stabilized PCE of 21.7% resulting from a 2D/3D bilayer PSC was reported. [49] However, the highest certified PCE in a 2D-only planar PSC is 15.3%, [50] which is far below that of their 3D perovskite-based counterparts. It thus stimulates the interest to develop new classes of materials which can solve the issues of toxicity and stability while still maintaining the fascinating properties of lead-based perovskite materials.Recent theoretical calculations demonstrate that a halide double perovskite structure, A 2 B′B″X 6 , which could be formed through a replacement of two toxic Pb 2+ in the crystal lattice with a pair of nontoxic heterovalent (i.e., monovalent and trivalent) metal cations, is a promising alternative to realize high-performance, lead-free, and stable PSCs. [51,52] Although, spectroscopic limited maximum efficiency (SLME) calculations revealed an efficiency limit less than 8% for the most prominent member www.advancedsciencenews.com double perovskites with a vacancy ordered structure. [88] In particular, the unit cell axis of Cs 2 AgBiBr 6 is given to be ≈11.25 Å, [25] which is two times larger than that of MAPbBr 3 (≈5.92 Å). [89] Both Ag + and Bi 3+ occupy the B-site of the crystal lattice with slightly varied metal-halide bond lengths. The dissimilar bond lengths st...

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Section: + /Bi 3+ Halide Double Perovskitesmentioning

confidence: 76%

Progress of Lead‐Free Halide Double Perovskites

Igbari

Wang

Liao

2019

Advanced Energy Materials

343

297

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“…Du et al have demonstrated bandgap engineering of Cs 2 AgBiBr 6 through alloying of trivalent cations such as Sb 3+ . [198] They found that the narrowed bandgap is partially retainable after releasing the pressure. [197] The bandgap reduction is attributed to the higher energy levels of Sb 5s states than that of Bi 6s states, which slightly raises the VBM.…”

Section: D a 2 B(i)b(ii)x 6 Halide Double Perovskitesmentioning

confidence: 99%

From Lead Halide Perovskites to Lead‐Free Metal Halide Perovskites and Perovskite Derivatives

2019

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serious challenges due to the inclusion of toxic Pb and instability against moisture, heat, and irradiation. In recent years, significant efforts have been paid to develop Pb-free halide perovskite and perovskite derivative absorber materials. However, so far, solar cells based on these materials show significantly inferior performances as compared to their Pb halide perovskite counterparts. Herein, we provide reviews on the fundamental understandings of the photovoltaic properties from Pb halide perovskites to Pb-free metal halide perovskites and perovskite derivatives as well as the experimental results reported in the literature. The results suggest that replacing Pb by nontoxic elements may degrade the superior photovoltaic properties seen in Pb halide perovskites, explaining the fact that all reported solar cells based on Pb-free perovskites or perovskite derivatives show performances significantly lower than Pb halide perovskite solar cells. Overview: Approaches and Consequences of Pb ReplacementWe first provide an overview of the approaches and consequences of Pb replacement reported in the literature, as shown in Figure 1. In general, there are two categories for Pb replacement: using either homovalent elements such as Sn and Ge or heterovalent elements such as Bi and Sb. The heterovalent replacement category can be divided into two subcategories based on the ways to maintain the charge neutrality: ion-splitting and ordered vacancy. The ion-splitting subcategory can be further divided into mixed anion compounds with the formula of AB(Ch,X) 3 , where Ch represents a chalcogen element, and X represents a halogen element, and mixed cation compounds with a formula of A 2 B(I)B(III)X 6 , which are commonly called double perovskites. The ordered vacancy subcategory can also be divided into the B(III) compounds with a formula of A 3 ◻B(III)X 9 and the B(IV) compounds with a formula of A 2 ◻ B(IV)X 6 (the sign of ◻ indicates vacancy). Figure 1 also summarizes the photovoltaic properties and the stabilities of each group of materials, which provides a clear overview of the consequences of Pb replacement. While the homovalent replacement by Sn or Ge leads to instability, the heterovalent Pb replacement leads to degraded electronic properties mainly due to the reduction on electronic dimensionality. As a result, all the reported Pb-free perovskite and perovskite derivative solar Despite the exciting progress on power conversion efficiencies, the commercialization of the emerging lead (Pb) halide perovskite solar cell technology still faces significant challenges, one of which is the inclusion of toxic Pb. Searching for Pb-free perovskite solar cell absorbers is currently an attractive research direction. The approaches used for and the consequences of Pb replacement are reviewed herein. Reviews on the theoretical understanding of the electronic, optical, and defect properties of Pb and Pb-free halide perovskites and perovskite derivatives are provided, as well as the experimental results available in the literature....

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“…[47] Notably, at 3.1 GPa, the inclined upward straight lines tend to bend towards the Z ′ axis ( Figure S1b, Supporting Information), which indicated that pressure induced the ionic transport behavior to electrical transport behavior transition. Jaffe et al [48] and Li et al [42] reported that similar structural amorphization contributed to the continuous band gap narrowing at higher pressure before. Thus, the observed ionic transport to electrical transport behavior transition should be induced by the phase transition when phase III becomes dominant.…”

mentioning

confidence: 91%

“…[42] They found that the band gap of Cs 2 AgBiBr 6 started to decrease above 6.5 GPa. At higher pressure, and especially after the third phase transition, only five broad peaks were left.…”

mentioning

confidence: 99%

Large Band Gap Narrowing and Prolonged Carrier Lifetime of (C₄H₉NH₃)₂PbI₄ under High Pressure

Yuan

Liu

et al. 2019

Advanced Science

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Due to their superior optical and electronic properties and good stability, 2D organic–inorganic halide perovskites (OIHPs) exhibit strong potential for optoelectronic applications. However, the large band gap, short carrier lifetime, and high resistance hinder their practical performance. In this work, the band gap is successfully tuned, the carrier lifetime is prolonged, and the resistance of (C 4 H 9 NH 3 ) 2 PbI 4 (BA 2 PbI 4 ) is reduced directly using high pressure. The band gap is decreased to less than 1 eV at 35.0 GPa, and the highest pressure is studied. The carrier lifetime at 9.9 GPa is 20 times longer than that at ambient conditions. Moreover, the resistance is reduced by four orders of magnitude at 34.0 GPa accompanying band gap narrowing. This work indicates that pressure plays an effective role in tuning the optical and electronic structures of BA 2 PbI 4 , and also provides a strategy to synthesize high‐performance OIHP materials.

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High‐Pressure Band‐Gap Engineering in Lead‐Free Cs₂AgBiBr₆ Double Perovskite

Cited by 210 publications

References 33 publications

Progress of Lead‐Free Halide Double Perovskites

Progress of Lead‐Free Halide Double Perovskites

From Lead Halide Perovskites to Lead‐Free Metal Halide Perovskites and Perovskite Derivatives

Large Band Gap Narrowing and Prolonged Carrier Lifetime of (C₄H₉NH₃)₂PbI₄ under High Pressure

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High‐Pressure Band‐Gap Engineering in Lead‐Free Cs2AgBiBr6 Double Perovskite

Cited by 210 publications

References 33 publications

Progress of Lead‐Free Halide Double Perovskites

Progress of Lead‐Free Halide Double Perovskites

From Lead Halide Perovskites to Lead‐Free Metal Halide Perovskites and Perovskite Derivatives

Large Band Gap Narrowing and Prolonged Carrier Lifetime of (C4H9NH3)2PbI4 under High Pressure

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High‐Pressure Band‐Gap Engineering in Lead‐Free Cs₂AgBiBr₆ Double Perovskite

Large Band Gap Narrowing and Prolonged Carrier Lifetime of (C₄H₉NH₃)₂PbI₄ under High Pressure