Proceedings of Perovskite Thin Film Photovoltaics (ABXPV17)
Publication date: 18th December 2016
Solar cells based on APbX3 halide perovskites with (A = CH3NH3, HC(NH2)2, Cs and X = Br, Cl, I) have shown record efficiencies of up to 21.1%.1 However, there are concerns related to these absorbers, such as the toxicity of Pb and solar cell instability from UV induced damage to the organic component. One route to reduce the toxicity of the absorber material is replacing Pb by Sn. Moreover, completely substituting the organic cation(s) with (inorganic) Cs can improve device longevity.2 Incorporating these modifications leads to a class of inorganic Pb-free perovskites – CsSnX3 – as promising alternative absorbers. Devices based on CsSnX3 have thus far exhibited only relatively low efficiencies, possibly due to the oxidization from Sn+2 to Sn+4 producing deep defects in the absorber.3 Adding SnF2 during preparation inhibits this oxidation,4 however, the exact mechanism behind the SnF2 treatment, in particular its impact on the electronic structure, is not yet fully understood. Another approach to preventing Sn oxidation is changing the deposition environment/technique. Sn is more likely to oxidize when CsSnX3 is prepared wet-chemically (e.g., via spin-coating) than if it is prepared by thermal evaporation under vacuum conditions. For the latter, depositing the absorber in ultra-high vacuum (UHV) allows preparation of films without Sn oxidation.
To identify the roles of the SnF2 treatment, halide composition, and deposition route, thin films of (spin-coated) CsSnBr3/compact-TiO2/FTO/glass and (UHV deposited) CsSnCl3/Mo/glass were characterized by hard x-ray photoelectron spectroscopy (HAXPES). We find improved substrate coverage when SnF2 is added to the precursor solution or when the absorber is deposited via thermal evaporation in UHV. Furthermore, we can identify different chemical species depending on the preparation process. Our measurements also reveal an impact of the SnF2 treatments on the perovskite electronic structure, i.e., it enhances the density of states close to the valence band maximum (VBM). Also, we find a VBM shift of approximately 1 eV away from the Fermi level if CsSnCl3 is compared to CsSnBr3.
In our contribution, we will discuss in detail the chemical and electronic properties of inorganic Pb-free perovskites. These findings can lead to insights required to identify pathways for efficiency improvements of solar devices based on solution- and thermal-deposition-processed CsSnX3 perovskite absorber layers.
1Saliba et al., Energy Environ. Sci.9 (2016)1989.
2Kulbak et al., J. Phys. Chem. Lett. 7 (2015) 167.
3Chung et al., J. Am. Chem. Soc. 134 (2012) 8579.
4Kumar et al., Adv. Mater. 26 (2014) 7122.
nanoGe is a prestigious brand of successful science conferences that are developed along the year in different areas of the world since 2009. Our worldwide conferences cover cutting-edge materials topics like perovskite solar cells, photovoltaics, optoelectronics, solar fuel conversion, surface science, catalysis and two-dimensional materials, among many others.
nanoGe Fall Meeting (NFM) is a multiple symposia conference celebrated yearly and focused on a broad set of topics of advanced materials preparation, their fundamental properties, and their applications, in fields such as renewable energy, photovoltaics, lighting, semiconductor quantum dots, 2-D materials synthesis, charge carriers dynamics, microscopy and spectroscopy semiconductors fundamentals, etc.
This conference is a unique series of symposia focused on advanced materials preparation and fundamental properties and their applications, in fields such as renewable energy (photovoltaics, batteries), lighting, semiconductor quantum dots, 2-D materials synthesis and semiconductors fundamentals, bioimaging, etc.
International Conference on Hybrid and Organic Photovoltaics
International Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
The main topics of the Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP) are discussed every year in Asia-Pacific for gathering the recent advances in the fields of material preparation, modeling and fabrication of perovskite and hybrid and organic materials. Photovoltaic devices are analyzed from fundamental physics and materials properties to a broad set of applications. The conference also covers the developments of perovskite optoelectronics, including light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.
The International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics (NIPHO) is the best place to hear the latest developments in perovskite solar cells as well as on recent advances in the fields of perovskite light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.