Improving the stability of methylammonium lead iodide perovskite solar cells by cesium doping

Fan, Yuman; Qin, Helin; Ye, Wang; Liu, Meizhuang; Huang, Feng; Zhong, Dingyong

doi:10.1016/j.tsf.2018.10.001

Cited by 28 publications

(16 citation statements)

References 38 publications

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“…We find that the binding energies (BE) of elemental core levels shift to higher (≈0.24 eV) BE as the alkali-metal-cation concentration increases, which follows the trend in the UPS data shown in Figure . This upshift is also consistent with previous studies of Cs + - and K + -contained mixed-cation perovskite films. , These upshifts for both of the core levels from XPS and VBM from UPS indicate slight n-doping of the films as the Fermi level shifts toward the conduction band edge.…”

Section: Resultssupporting

confidence: 92%

Role of Alkali-Metal Cations in Electronic Structure and Halide Segregation of Hybrid Perovskites

Zhang

Tang

Fan

et al. 2020

ACS Appl. Mater. Interfaces

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The ability to control or prevent phase segregation in perovskites is crucial to realizing stable and tunable mixed-halide optoelectronic devices. In this work, we systematically examine the impact of alkali-metal-cation (Cs+ and K+) concentration on the band structure, chemical composition, phase segregation, and polycrystalline microstructure on formamidinium-dominated mixed-halide mixed-cation perovskite films. It was found that the incorporation of Cs+ and K+ cations decreases the work function and the core levels of all components shift toward higher binding energy consistent with n-doping the perovskite film, which facilitates electron transfer to the electron transport layer TiO2. A concentration-dependent film structure was observed by X-ray photoemission spectroscopy and grazing incidence wide-angle X-ray scattering where the halides and cations are distributed evenly across perovskite films at low metallic cation concentration (5%). A high metal-cation ratio (20%) leads to halide segregation within the perovskite film and the surface becomes bromide-poor, whereas the bromide and metal cations diffuse more deeply within the film. These differences in electronic properties, element distribution, and film morphology were reflected in the device performance where the power conversion efficiency of low-metallic-cation concentration (5% of Cs+ and K+) perovskite solar cells is ≈5% higher than the high-concentration ones (20%). This study provides valuable chemical and physical insight into the underlying trade-offs in the careful tuning of electrical properties and film structure to optimize multication and mixed-halide hybrid perovskites.

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Section: Resultssupporting

confidence: 92%

Role of Alkali-Metal Cations in Electronic Structure and Halide Segregation of Hybrid Perovskites

Zhang

Tang

Fan

et al. 2020

ACS Appl. Mater. Interfaces

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“…The C 1s peaks at ∼286.5 eV may correspond to a C−C bond from organic contamination, and that at ∼288.5 eV may correspond to a C−N bond from FA or MA part. The C 1s peaks slightly shifted to larger energy compared with some reported positions, 39,40 possibly due to the surface charging, but the peak positions were comparable in the three samples. There were also no significant differences in peak position and intensity for the peaks of Pb 4f (∼138.8 and ∼143.6 eV) and I 3d (∼619.7 and ∼631.2 eV) 26 in all the samples.…”

Section: Resultsmentioning

confidence: 60%

Perovskite Solar Cells with >19% Efficiency Achieved by an Advanced Three-Step Method Using Additional HC(NH₂)₂I–NaI Spin-Coating

Okamoto¹,

Sumiya

Suzuki³

2019

ACS Appl. Energy Mater.

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Recently, a doping of sodium ion (Na + ) into the perovskite solar cells has attracted much attention. Supposing that the Na + ions substitute the A-site cation of the perovskite structure, the Na + doping is expected to enlarge a bandgap of perovskite layer. Additionally, the Na + doping may increase the grain size and decrease the trap density. We recently reported a new 3-step method using additional spin-coating of a HC-(NH 2 ) 2 I (FAI) solution on a 2-step prepared CH 3 NH 3 PbI 3 (MAPbI 3 ) layer containing an unreacted PbI 2 , which produced a multiple bandgap structure by forming a FA-rich layer with a smaller bandgap near the electron transport layer. Here, we attempted to form the top layer with larger bandgap by adding a small amount of NaI into the FAI solution for the third step and investigated the effect of NaI post-treatment on the perovskite layer. The NaI addition slightly enlarged the bandgap of surface of the perovskite layer. Additionally, it accelerated the grain growth and effectively decreased grain boundaries, while the Na + tended to increase nonradiative recombination. As a result, the NaI addition enhanced the power conversion efficiency from 18.12% (FAI only) to 19.07% (with NaI addition) without degrading stability in air. The appropriate amount of NaI addition on the FAI solution is beneficial to boost the photovoltaic performance.

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“…Another option for obtaining the highest power conversion efficiencies is mesoporous bulk heterojunction cells; these, however, typically contain expensive chargetransport-and-blocking layers, which need high-temperature (400÷500 °C) [32]- [34] sintering, thus increasing the processing time and the cost of the solar cell. To overcome these drawbacks, a low-temperatureprocessed inverted planar p|i|n solar cell could be produced using poly(3,4-ethylenedioxythiophene) poly(styrenesulphonate) (PEDOT:PSS) as the hole-transport (p) and electron-blocking layer material, while the phenyl-C 61 -butyric acid methyl ester (PCBM or, more specifically, PC 61 BM) is employed in the electron transport (n) layer (ETL), as frequently done in the design of planar inverted hybrid solar cells [28], [35], [44]- [46], [36]- [43].…”

Section: Discussionmentioning

confidence: 99%

Perovskite CH₃NH₃PbI_3–XCl_x Solar Cells and their Degradation (Part 1: A Short Review)

Kaulachs

Иванова

Tokmakov

et al. 2021

Latvian Journal of Physics and Technical Sciences

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Development of hybrid organic-inorganic perovskite solar cells (PSC) has been one of the hottest research topics since 2013. Within brief literature review, we would like to achieve two objectives. Firstly, we would like to indicate that a whole set of physical properties, such as high change carrier mobility, very low recombination rates, large carrier life time and diffusion length, large absorption coefficients and very weak exciton binding energies, are defining high power conversion efficiency (PCE) of methyl ammonium lead trihalide SC. The second objective is to draw attention to some, in our opinion, important aspects that previously have not been satisfactory addressed in literature. Although degradation of PSC is widely discussed, processes at very first exposure to ambient conditions after deposition of top electrode are uncovered.

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Improving the stability of methylammonium lead iodide perovskite solar cells by cesium doping

Cited by 28 publications

References 38 publications

Role of Alkali-Metal Cations in Electronic Structure and Halide Segregation of Hybrid Perovskites

Role of Alkali-Metal Cations in Electronic Structure and Halide Segregation of Hybrid Perovskites

Perovskite Solar Cells with >19% Efficiency Achieved by an Advanced Three-Step Method Using Additional HC(NH₂)₂I–NaI Spin-Coating

Perovskite CH₃NH₃PbI_3–XCl_x Solar Cells and their Degradation (Part 1: A Short Review)

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Improving the stability of methylammonium lead iodide perovskite solar cells by cesium doping

Cited by 28 publications

References 38 publications

Role of Alkali-Metal Cations in Electronic Structure and Halide Segregation of Hybrid Perovskites

Role of Alkali-Metal Cations in Electronic Structure and Halide Segregation of Hybrid Perovskites

Perovskite Solar Cells with >19% Efficiency Achieved by an Advanced Three-Step Method Using Additional HC(NH2)2I–NaI Spin-Coating

Perovskite CH3NH3PbI3–XClx Solar Cells and their Degradation (Part 1: A Short Review)

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Perovskite Solar Cells with >19% Efficiency Achieved by an Advanced Three-Step Method Using Additional HC(NH₂)₂I–NaI Spin-Coating

Perovskite CH₃NH₃PbI_3–XCl_x Solar Cells and their Degradation (Part 1: A Short Review)