Indium-Free Perovskite Solar Cells Enabled by Impermeable Tin-Oxide Electron Extraction Layers.

Hu, Ting; Becker, Tim; Pourdavoud, Neda; Zhao, Jie; Brinkmann, Kai Oliver; Heiderhoff, Ralf; Gahlmann, Tobias; Huang, Zengqi et al. · Adv Mater · 2017

basic_science · Level V

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Abstract

Corrosive precursors used for the preparation of organic-inorganic hybrid perovskite photoactive layers prevent the application of ultrathin metal layers as semitransparent bottom electrodes in perovskite solar cells (PVSCs). This study introduces tin-oxide (SnO<sub>x</sub> ) grown by atomic layer deposition (ALD), whose outstanding permeation barrier properties enable the design of an indium-tin-oxide (ITO)-free semitransparent bottom electrode (SnO<sub>x</sub> /Ag or Cu/SnO<sub>x</sub> ), in which the metal is efficiently protected against corrosion. Simultaneously, SnO<sub>x</sub> functions as an electron extraction layer. We unravel the spontaneous formation of a PbI<sub>2</sub> interfacial layer between SnO<sub>x</sub> and the CH<sub>3</sub> NH<sub>3</sub> PbI<sub>3</sub> perovskite. An interface dipole between SnO<sub>x</sub> and this PbI<sub>2</sub> layer is found, which depends on the oxidant (water, ozone, or oxygen plasma) used for the ALD growth of SnO<sub>x</sub> . An electron extraction barrier between perovskite and PbI<sub>2</sub> is identified, which is the lowest in devices based on SnO<sub>x</sub> grown with ozone. The resulting PVSCs are hysteresis-free with a stable power conversion efficiency (PCE) of 15.3% and a remarkably high open circuit voltage of 1.17 V. The ITO-free analogues still achieve a high PCE of 11%.