Passivation of grain boundaries and chemical stability in organic-inorganic lead halide perovskite solar cells

From QCLab
  • Speaker: William Jo (Ewha Womans University)
  • Date: Wednesday, April 06, 2016, at 17:00
  • Place: Jeongho Seminar Room

Organic-inorganic halide CH3NH3Pb(I,Br)3 perovskites is one of the most promising photovoltaic materials [1]. Perovskite solar cells have many advantageous for solar cell such as a large absorption coefficient, high carrier mobility, high carrier diffusion length, and direct band gap. We explored electrical properties of CH3NH3(Pb,Sn)(I,Br)3 with the thickness of perovskite ~150 nm since it is interesting that the bandgap can be tuned by Pb/Sn and I/Br. Our best cell of perovskite has achieved ~14% conversion efficiency. A concern of environmental hazard of Pb draws attention of Sn but the chemical stability of Sn is very low. The fabricated perovskite solar cells have a glass/FTO/blocking-TiO2/mesoporous-TiO2/perovskite/HTM(Spiro-MeOTAD)/Ag. We investigated the grain boundary properties in perovskite solar cells with different Pb/Sn and I/Br ratio by Kelvin probe force microscopy, conductive atomic force and pieozoresponse force microscopy measurements. The electrical grain boundary properties (positively charged grain boundaries) are similar to the polycrystalline CIGS and CZTSSe thin-film solar cells. Especially, positively charged GBs grain boundaries is obtained. These positively charged grain boundaries could be enhanced electron-hole separation and suppressing recombination near grain boundaries for high efficiency in the perovskite solar cells.

[1] G. Y. Kim et al., Journal of Physical Chemistry Letters 6, 2355 (2015).