Nanoscale charge transport properties of perovskite solar cells with WSe2 flakes as protective layer for stable performance

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Organic-inorganic perovskite solar cells have become a promising technology for next generation solar cells due to their superior optoelectronic properties such as tunable low bandgap, long charge diffusion length, low exciton binding energy and balanced charge transport. The power conversion efficiency (PCE) of more than 20% have been obtained from low temperature solution processing. However, perovskite solar cells suffer from poor stability in presence of moisture inhibiting its commercialization. We report the use of WSe2 flakes as protective and charge transport layer. The synthesis of WSe2 was done by using Chemical Vapor Deposition (CVD) with a WO3 powder and Se pellets as the precursors at a temperature zone of 260-270 deg. Cent. It is found that an atomically thin layer of WSe2 helps to increase the stability and charge transport properties due to its higher mobility and conductivity than widely used conventional hole transport material such as Spiro-OMeTAD. Transient photovoltage measurements shows that a thin layer of WSe2 increases the life time of carrier by suppressing the back recombination of electrons from TiO2 and holes from perovskite with proper band alignment between perovskite and hole transport layer, which we will elaborate upon in this work.

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Journal: TechConnect Briefs
Volume: 2, Materials for Energy, Efficiency and Sustainability: TechConnect Briefs 2017
Published: May 14, 2017
Pages: 37 - 40
Industry sector: Energy & Sustainability
Topic: Solar Technologies
ISBN: 978-0-9975117-9-6