First-principles insight into the photoelectronic properties of Ge-based perovskites

Lu, Xiaoqing; Zhongliang, Zhao; Li, Ké; Han, Zhaoxiang; Wei, Shuxian; Guo, Chen; Zhou, Sainan; Wu, Zhenhua; Guo, Wenyue; Wu, Chi‐Man Lawrence

doi:10.1039/c6ra18534g

Cited by 52 publications

(43 citation statements)

References 30 publications

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“…[75] Theoretical studies have shown that these Ge halide perovskites exhibit promising optoelectronic properties for solar cell applications. [74][75][76][77][78][79][80][81] Taking CsGeI 3 as an example, the calculated band structure shows a direct bandgap at the Z point, as shown in Figure 7d. [75] The VBM consists of antibonding states of Ge 4s and I 5p orbitals.…”

Section: Wwwadvmatde Wwwadvancedsciencenewscommentioning

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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Section: Wwwadvmatde Wwwadvancedsciencenewscommentioning

confidence: 99%

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

2019

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“…MAGeI 3 has an optical bandgap 1.63 eV which is greater in magnitude than that of MAPbI 3 (1.55 eV) and MASnI 3 (1.30), excellent hole and electron conducting behavior and better stability in air as compared to MaPbI 3 . However, Ge 2+ cation being smaller in size (73 pm) deviates from its regular [GeI 6 ] octahedral center as it replaces cation of much larger ionic radius as that of Pb 2+ (119 pm) and Sn 2+ (110 pm) . As a consequence, it forms three short GeI bonds (2.73–2.77 Å) and three long in GeI bonds (3.26–3.58 Å).…”

Section: Lead‐free Perovskitesmentioning

confidence: 99%

“…However, Ge 2+ cation being smaller in size (73 pm) deviates from its regular [GeI 6 ] octahedral center as it replaces cation of much larger ionic radius as that of Pb 2+ (119 pm) and Sn 2+ (110 pm) . As a consequence, it forms three short GeI bonds (2.73–2.77 Å) and three long in GeI bonds (3.26–3.58 Å). The Ge‐based perovskites have been extensively studied by carrying computational work based on density functional theory (DFT) .…”

Section: Lead‐free Perovskitesmentioning

confidence: 99%

Potential Substitutes for Replacement of Lead in Perovskite Solar Cells: A Review

Kour¹,

et al. 2019

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Lead halide perovskites have displayed the highest solar power conversion efficiencies of 23% but the toxicity issues of these materials need to be addressed. Lead‐free perovskites have emerged as viable candidates for potential use as light harvesters to ensure clean and green photovoltaic technology. The substitution of lead by Sn, Ge, Bi, Sb, Cu and other potential candidates have reported efficiencies of up to 9%, but there is still a dire need to enhance their efficiencies and stability within the air. A comprehensive review is given on potential substitutes for lead‐free perovskites and their characteristic features like energy bandgaps and optical absorption as well as photovoltaic parameters like open‐circuit voltage (VOC), fill factor, short‐circuit current density (J SC), and the device architecture for their efficient use. Lead‐free perovskites do possess a suitable bandgap but have low efficiency. The use of additives has a significant effect on their efficiency and stability. The incorporation of cations like diethylammonium, phenylethyl ammonium, phenylethyl ammonium iodide, etc., or mixed cations at different compositions at the A‐site is reported with engineered bandgaps having significant efficiency and stability. Recent work on the advancement of lead‐free perovskites is also reviewed.

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“…However, in practice the Ge-based perovskites such as CsGeI 3 , MAGeI 3 , and FAGeI 3 displayed larger bandgaps (i.e., 1.63, 2.0, and 2.35 eV) than that of CH 3 NH 3 SnI 3 (1.30 eV) and CH 3 NH 3 PbI 3 (1.55 eV) [52]. The difference between experimental data and what we expected from high orbital energy is mainly due to the structural distortion of [GeI 6 ] octahedral as the small ionic radius (0.73 Å) of Ge 2+ substituting the bigger ionic radius of Pb 2+ (1.19 Å) or Sn 2+ (1.02 Å) [53]. Additionally, the Ge-based perovskites crystallize in polar space groups [54].…”

Section: Ge- Bi- Sb- and Cu-based Perovskitesmentioning

confidence: 64%

Quest for Lead-Free Perovskite-Based Solar Cells

Sajid¹,

Ji²,

Jiang³

et al. 2020

A Guide to Small-Scale Energy Harvesting Techniques

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Today, the perovskite solar cells (PSCs) are showing excellent potentials in terms of simple processing, abundance of materials, and architectural integration, as well as very promising device's power conversion efficiencies (PCEs), rocketed from 3.8% in 2009 to 23.3% in 2018. However, the toxic lead (Pb) element containing the chemical composition of typically used organic-inorganic halide perovskites hinders the practical applications of PSCs. This chapter starts with a general discussion on the perovskite crystal structure along with the serious efforts focused on Pb replacement in these devices. Section 2 will elaborate the fundamental features of tin (Sn)-based perovskites together with their performance in the PSCs. Other alternative elements, such as copper (Cu), germanium (Ge), bismuth (Bi), and antimony (Sb), will be discussed in Section 3. The end will summarize the challenges and opportunities based on the chapter contents.

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First-principles insight into the photoelectronic properties of Ge-based perovskites

Abstract: First-principles investigations were performed to elucidate the effects of A and X in Ge-based MAGeX3 perovskites (MA = CH3NH3+; X = Cl−, Br−, and I−) and AGeI3 (A = Cs+, CH3NH3+, HC(NH2)2+, CH3C(NH2)2+, and C(NH2)3+) on the photoelectronic properties.

Cited by 52 publications

References 30 publications

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

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

Potential Substitutes for Replacement of Lead in Perovskite Solar Cells: A Review

Quest for Lead-Free Perovskite-Based Solar Cells

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