Removal of Surface Oxygen Vacancies Increases Conductance Through TiO<sub>2</sub> Thin Films for Perovskite Solar Cells

Klasen, Alexander; Baumli, Philipp; Qu, Sanyin; Johannes, Ewald; Bretschneider, Simon A.; Hermes, Ilka; Bergmann, V.; Gort, Christopher; Axt, Amelie; Weber, Stefan A. L.; Kim, Heejae; Butt, Hans‐Jürgen; Tremel, Wolfgang; Berger, Rüdiger

doi:10.1021/acs.jpcc.9b02371

Cited by 69 publications

(61 citation statements)

References 43 publications

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“…We note that O 2 plasma treatment was performed because the TiO 2 ‐HCl film contains both surface and bulk (within TiO 2 nanoparticle; lower right in Figure a) oxygen vacancies, both of which increase the donor density of TiO 2 when employed as the ETL in PSC . The bulk vacancies improve the bulk conductivity, while the surface vacancies trigger the charge carrier recombination . Thus, removing surface vacancies yet retaining bulk vacancies in TiO 2 ETL by O 2 plasma exposure may lead to further improved performance of PSCs owing to suppressed photogenerated electron–hole recombination and the enhanced bulk conductivity.…”

Section: Resultsmentioning

confidence: 99%

Unconventional Route to Oxygen‐Vacancy‐Enabled Highly Efficient Electron Extraction and Transport in Perovskite Solar Cells

et al. 2019

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The ability to effectively transfer photoexcited electrons and holes is an important endeavor towardachieving high-efficiency solar energy conversion. Now,asimple yet robust acid-treatment strategy is used to judiciously create an amorphous TiO 2 buffer layer intimately situated on the anatase TiO 2 surface as an electron-transport layer (ETL) for efficient electron transport. The facile acid treatment is capable of weakening the bonding of zigzag octahedral chains in anatase TiO 2 ,therebyshortening staggered octahedron chains to form an amorphous buffer layer on the anatase TiO 2 surface.S uch amorphous TiO 2-coated ETL possesses an increased electron density owingt ot he presence of oxygen vacancies,l eading to efficient electron transfer from perovskite to TiO 2 .C ompared to pristine TiO 2-based devices,the perovskite solar cells (PSCs) with acid-treated TiO 2 ETL exhibit an enhanced short-circuit current and power conversion efficiency.

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Section: Resultsmentioning

confidence: 99%

Unconventional Route to Oxygen‐Vacancy‐Enabled Highly Efficient Electron Extraction and Transport in Perovskite Solar Cells

et al. 2019

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“…Oxygen has been shown to fill oxygen vacancies on the surface of TiO 2 or SnO 2 , either during the annealing process or upon oxygen plasma treatment which can be beneficial for the operation of PSCs. [231][232][233] Despite this, ZnO has often been introduced as an alternative metal oxide ETL due to its low processing temperature [170] and high electron mobility. [234] Unlike TiO 2 and SnO 2 , ZnO has been found to have undesirable side effects with MAPbI 3 where the nature of the ZnO surface leads to proton-transfer reactions at the ZnO/MAPbI 3 interface.…”

Section: Electron Transport Layermentioning

confidence: 99%

Ambient Fabrication of Organic–Inorganic Hybrid Perovskite Solar Cells

et al. 2020

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Unlike fossil fuels, the sun is an inexhaustible energy source that delivers more energy to the earth in 1 h than the entire planet consumes in one year. Energy can be harvested from the sun using photovoltaics (PV) and stored (e.g., batteries), meaning solar energy can be used as and when required. [3,4] Currently, the commercial PV market is dominated by single-junction crystalline silicon (c-Si) PV which deliver power conversion efficiencies (PCE) of over 26% under 1 Sun illumination (AM 1.5 standard). [5,6] Despite their high efficiencies, the fabrication of c-Si PV is nontrivial and lacks electronic tunability. Furthermore, the record efficiency for c-Si PV is 26.7% [5] which is very close to the theoretical limit of 29.4%. [7] This clearly indicates that c-Si PV is a mature technology and there is limited room for improvement. [8] Over the past two decades, third-generation solar cells such as dye-sensitized solar cells, [9,10] quantum dot solar cells, [11,12] organic solar cells, [13,14] and perovskite solar cells (PSCs) [15,16] have been developed as alternatives to c-Si technologies. Of these third-generation solar cells, single-junction PSCs have generated significant attention due to their intense visible to near-infrared absorptivity, [16-18] long diffusion lengths of the charge carriers, [19,20] high efficiency, [21,22] electronic and physical tunability, [23,24] and low manufacturing costs. [25,26] After the first report by Miyasaka's group in 2009, [27] the PCE for single junction devices increased considerably from 3.8% to 25.2%, [27,28] making it the fastest advancing PV technology to date. This has uniquely placed PSCs as the frontrunner technology to potentially replace or coexist with c-Si PV. The term "perovskite" refers to a group of compounds that share the same lattice structure as calcium titanium oxide (CaTiO 3). All PV perovskite materials have the general chemical formula ABX 3 , as illustrated in Figure 1a. Organic-Inorganic hybrid PSCs are typically made using an organic/ inorganic cation (A = methylammonium (MA) CH 3 NH 3 + , formamidinium (FA) CH 3 (NH 2) 2 + , or cesium), a divalent cation (B = Pb 2+ or Sn 2+) , [29] and an anion (X = Cl − , Br − , or I −), illustrated in Figure 1b. [16,30] A is surrounded by eight lead halide octahedra (B in the center of octahedra) and forms a cubic perovskite structure. When the size of A or/and X is changed, the structure of perovskite will distort. The Goldschmidt tolerance factor (t) [31] of perovskite is an empirical index for Organic-inorganic hybrid perovskite solar cells (PSCs) have attracted significant attention in recent years due to their high-power conversion efficiency, simple fabrication, and low material cost. However, due to their high sensitivity to moisture and oxygen, high efficiency PSCs are mainly constructed in an inert environment. This has led to significant concerns associated with the long-term stability and manufacturing costs, which are some of the major limitations for the commercialization of this cutting-edge tech...

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“…Correspondingly, OVs are present on the surface to maintain the charge equilibrium. In the O 1s spectra (Figure 5d), the main peak of O 1s at 529.9 eV is assigned to TiO lattice bond without nearby OVs, [ 26 ] while the shoulder peak at 531.8 eV belongs to O‐atoms in the vicinity of an O‐vacancy. [ 12a ] It has been reported that OVs may induce dissociation of H 2 O and chemisorption of OH ‐ at OV sites.…”

Section: Resultsmentioning

confidence: 99%

Flame Synthesized Blue TiO₂₋_x with Tunable Oxygen Vacancies from Surface to Grain Boundary to Bulk

Manuputty

Yuan

et al. 2020

Small Methods

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Fabrication of nonstoichiometric metal oxides containing oxygen vacancies (OVs) has been an effective strategy to modulate their (photo)catalytic or (photo)electrochemical performances which are all affected by charge transfer at the interface and in the bulk. Considerable efforts are still needed to achieve tunability of OVs, as well as their quantitative characterization. Herein, a one‐step flame synthesis method is reported for the first time for fast fabrication of blue TiO2−x with controllable defect content and location. Temperature‐programmed oxidation (TPO) analysis is applied for the first time and found to be an excellent technique in both differentiating and quantifying OVs at the surface, grain boundary (GB), and bulk of TiO2−x. The results indicate that a moderate level of OVs can greatly enhance the charge transfer. Importantly, the OVs locked at GBs due to the thermal sintering of nanoparticles during the synthesis can facilitate the anchoring and reduction of Pt species.

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Removal of Surface Oxygen Vacancies Increases Conductance Through TiO₂ Thin Films for Perovskite Solar Cells

Cited by 69 publications

References 43 publications

Unconventional Route to Oxygen‐Vacancy‐Enabled Highly Efficient Electron Extraction and Transport in Perovskite Solar Cells

Unconventional Route to Oxygen‐Vacancy‐Enabled Highly Efficient Electron Extraction and Transport in Perovskite Solar Cells

Ambient Fabrication of Organic–Inorganic Hybrid Perovskite Solar Cells

Flame Synthesized Blue TiO₂₋_x with Tunable Oxygen Vacancies from Surface to Grain Boundary to Bulk

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Removal of Surface Oxygen Vacancies Increases Conductance Through TiO2 Thin Films for Perovskite Solar Cells

Cited by 69 publications

References 43 publications

Unconventional Route to Oxygen‐Vacancy‐Enabled Highly Efficient Electron Extraction and Transport in Perovskite Solar Cells

Unconventional Route to Oxygen‐Vacancy‐Enabled Highly Efficient Electron Extraction and Transport in Perovskite Solar Cells

Ambient Fabrication of Organic–Inorganic Hybrid Perovskite Solar Cells

Flame Synthesized Blue TiO2−x with Tunable Oxygen Vacancies from Surface to Grain Boundary to Bulk

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Product

Resources

About

Removal of Surface Oxygen Vacancies Increases Conductance Through TiO₂ Thin Films for Perovskite Solar Cells

Flame Synthesized Blue TiO₂₋_x with Tunable Oxygen Vacancies from Surface to Grain Boundary to Bulk