Highly Oriented Stable Thin Films of γ-CsPbI3: Fabrication from MoS2 Induced Sonochemically Synthesized Colloidal Nanocrystals and the Degradation Studies
Anjani Nagvenkar a b, Laxman Gouda a, Ilana Perelshtein a, Aharon Gedanken a
a Institute of Nanotechnology and Advance Materials,Bar-Ilan university, Ramat-Gan, Ramat-Gan, 52900, Israel
b Technion - Israel Institute of Technology, Haifa, Israel
nanoGe Perovskite Conferences
Proceedings of nanoGe International Conference on Perovskite Solar Cells, Photonics and Optoelectronics (NIPHO19)
International Conference on Perovskite Thin Film Photovoltaics
Jerusalem, Israel, 2019 February 24th - 27th
Organizers: Lioz Etgar and Kai Zhu
Poster, Anjani Nagvenkar, 071
DOI: https://doi.org/10.29363/nanoge.nipho.2019.071
Publication date: 21st November 2018

CsPbI3 is known to exhibit the most suitable low band gap for photovoltaic application among all-inorganic lead halide pervoskites. However stabilizing the cubic α-phase of CsPbI3 has been a challenge in the photovoltaics research as it readily transforms into non-perovskite orthorhombic δ-CsPbI3. Recently, an intermediate metastable perovskite black phase γ-CsPbI3 is being reported with stability higher than its alpha analogue due to its lower surface free energy. Herein, we report a facile synthesis of γ-CsPbI3 colloidal nanocrystals induced by MoS2 with ultrasound mediated process. The presence of MoS2 significantly influences the nanocrystal formation. A substantial phase-stabilty of γ-CsPbI3 is obtained in the colloidal solution. The thin film fabricated from the solution by simple one-step spin coating process also showed high stability of over 1 month under nitrogen atmosphere. The degradation profile (conversion from γ- to δ-CsPbI3) under ambient air of the thin films were studied with absorbance, Raman, SEM, and photoluminescence (PL) measurements. The absorbance and Raman degradation patterns illustrated significant variations in the morphology and crystal structure. Besides, the effect of substrate temperature on the spin coating is demonstrated and observed to differ. The present study is a first report using transition metal chalcogenide (TMD) to promote the formation and stabilize the phase of lead halide perovskites, which can open new research platforms in this direction.

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