Electronic structure of hybrid perovskites - a new generation of solar cells

Project: Award Project

Description

Hybrid (organic-inorganic) solar cells with a perovskite structure are attracting increasing attention caused by the excellent photoelectric characteristics due to the high absorption coefficient, the balanced nature of the charge transfer and the low density of the traps. For the first time such elements were proposed by Miyasaka et al. in 2009 [1], as well as Park et al. in 2011 [2], where the hybrid perovskite of MAPbX3 type (where MA (methylamine) = CH3NH3, X (halide) = I or Br) was used as an inorganic sensitizer. In the future, the number of such publications is growing rapidly and reaches first 56 in 2013, then 460 in 2014 and, finally, 900 in 2015 [3]. The main advantage of hybrid perovskites is the simplicity of their production from conventional metal salts and industrial chemical organic compounds, rather than from expensive and rare elements used in high-performance semiconductor analogs, such as solar cells based on silicon and gallium arsenide. It is equally important that perovskite based materials can be used to print photoelectronics not only on glass, but also on other materials and surfaces. This makes such batteries much cheaper than with more complex methods of producing existing thin-film solar cells based on Si or GaAs. Great progress was made in increasing the efficiency of perovskite solar cells, which increased from 3.8% in 2009 [1] to 22.1% in early 2016 [4, 5]. However, despite their high efficiency and relatively low cost, the perovskite solar cells exhibit unstable properties that limit the commercial production of such materials in the future and become the main problem that must be urgently investigated and solved. To understand the basis for the degradation of these materials and to propose solutions to this problem, two factors will be studied in this project: the photostability and thermal stability of perovskite solar cells. Both these factors will be investigated on the basis of detailed studies of the electronic structure by means of measurements of X-ray photoelectron spectra (core levels and valence bands) that are sensitive to chemical bonding and its changes caused by photo- and thermodegradation. In this project we will study the effect of photo and thermal stability of hybrid perovskites on x-ray photoelectron spectra depending on: 1. Type of cation and anion: MAPbI3, MAPbBr3, FAPbBr3, CsPbI3, CsPbBr3, MAPbI2.7Br0.3, MAPbI2.7Cl0.3. 2. Type of substrates: ITO, FTO, glass, MoO3, ITO/PEDOT:PSS, ITO/TiO2, glass/PEDOT:PSS, glass/TiO2, FTO/TiO2. Sample preparation will be done by Institute of Problems of Chemical Physics of RAS. Photo irradiation and annealing at a temperature of 70-90 °C for 50-300 hours will be carried out inside the glove box without access to oxygen and air moisture. To increase the reliability of the conclusions made on the basis of measurements of X-ray photoelectron spectra, the analysis of the results will be carried out on the basis of a set of 5 parameters: - the chemical composition of the surface, - the fine structure of XPS C 1s and N 1s spectra, - chemical shift of Pb 4f7/2, 4f5/2-spectra, - chemical shift of XPS I (Br) 3d5/2, 3d3/2-spectra, - fine structure and energy position of XPS valence spectra. All XPS measurements will be performed on one of the world's best laboratory X-ray photoelectronic spectrometer (PHI XPS 5000 VersaProbe spectrometer (ULVAC-Physical Electronics, USA) with Al Kα monochromatic radiation (E = 1486.6 eV) and high spatial (100 μm) and energy (≤ 0.5 eV) resolution in vacuum (10^-7 Pa), and numerical calculations of the electronic structure will be performed using well-proven methods of the density functional theory, including the available WIEN2k, SIESTA, and others codes. References: 1. Kojima, A .; Teshima, K .; Shirai, Y .; Miyasaka, T. Organometal halide perovskites as visible-light sensitizers for photovoltaic cells. J. Am. Chem. Soc. 131 (2009) 6050-6051. 2. Im, J.-H .; Lee, C.-R .; Lee, J.-W .; Park, S.-W .; Park, N.-G. 6.5% efficient perovskite quantum-dot-sensitized solar cell. Nanoscale 3 (2011) 4088-4093. 3. Xing Zhao and Nam-Gyu Park, Stability Issues on Perovskite Solar Cells, Photonics 2 (2015), 1139-1151. 4. Polman A, Knight M, Garnett E C, Ehrler B and Sinke W C 2016 Photovoltaic materials: present efficiencies and future challenges Science 352 (2016) 4424. 5. NREL research cell efficiency records www.nrel.gov/ncpv/ images / efficiency_chart.jpg
StatusFinished
Effective start/end date01/01/201730/06/2019

Keywords

  • 29.19.25
  • RNF
  • Mira Research Division