Cesium Titanium(IV) Bromide Thin Films Based Stable Lead-free Perovskite Solar Cells

Chen, Min; Ju, Ming‐Gang; Carl, Alexander D.; Zong, Yanbing; Grimm, Ronald L.; Gu, Jiajun; Zeng, Xiao Cheng; Zhou, Yuanyuan; Padture, Nitin P.

doi:10.1016/j.joule.2018.01.009

Cited by 476 publications

(438 citation statements)

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“…Among the many A 2 BX 6 compounds, [96][97][98][99] A 2 SnI 6 (A = Cs, MA), [100][101][102][103][104][105][106][107][108][109] Cs 2 PdBr 6 , [110,111] and Cs 2 TiBr 6 [112,113] have been investigated for photovoltaic applications. As the [BX 6 ] octahedra in A 2 BX 6 compounds are isolated, the optoelectronic properties of these compounds are rather different from those of 3D ABX 3 (B = Pb, Sn, and Ge) halide perovskites.…”

Section: A 2 B(iv)x 6 Perovskite Variantsmentioning

confidence: 99%

“…As shown in Figure 9a-c, [101,110,112] the VBMs of these compounds consist of nonbonding X p orbitals, rather than the cation lonepair s-X p antibonding states for ABX 3 (B = Pb, Sn, and Ge) halide perovskites. [102,109,113,115] Despite the general similarity, there are some differences in the optoelectronic properties of these compounds. The CBMs are derived from the antibonding states of cation s or d and X p orbitals.…”

Section: A 2 B(iv)x 6 Perovskite Variantsmentioning

confidence: 99%

“…[102,109,113,115] Despite the general similarity, there are some differences in the optoelectronic properties of these compounds. [112] Figure 10a-c shows the measured optical absorption and PL spectra of Cs 2 SnI 6 , [105] Cs 2 PdBr 6 , [110] and Cs 2 TiBr 6 , [113] respectively. [101] However, the transition from the VBM to the CBM is dipole-forbidden.…”

Section: A 2 B(iv)x 6 Perovskite Variantsmentioning

confidence: 99%

“…For Cs 2 TiBr 6 , the isolated conduction band is more localized than that of Cs 2 PbBr 6 , due to the more localized orbital character of Ti 3d than Pd 4d orbitals. [113] It would be interesting to see if further efficiency enhancement can be achieved for such 0D Cs 2 TiBr 6 -based solar cells in further studies. Taking Cs 2 SnI 6 as an example, [102] Figure 9d shows the calculated charge-state transition levels of the intrinsic defects.…”

Section: A 2 B(iv)x 6 Perovskite Variantsmentioning

confidence: 99%

“…b) Band structure and density of states of Cs 3 Bi 2 I 9 crystals; the direct and indirect transitions are denoted by red and cyan arrows, respectively. [113] Copyright 2018, Elsevier Inc. d) J-V characteristic curves of a series of "sandwich" typed cells with different composition of Cs 2 SnI 6−x Br x . [120] Copyright 2017, American Chemical Society.…”

Section: Wwwadvmatde Wwwadvancedsciencenewscommentioning

confidence: 99%

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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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