Band‐Engineered PbS Nanoparticles in CH3NH3PbI3 Solar Cells to Extend Activity Toward Near‐Infrared Region

Uttiya Dasgupta; Biswajit Kundu; Amlan J. Pal

Index: 10.1002/solr.201800012

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Abstract

Here, a route is reported to extend the activity of perovskite solar cells toward the near‐infrared (NIR) region through incorporation of band‐engineered PbS nanoparticles in the form of a bilayer structure with the perovskite layer. The nanoparticles were doped with a heterovalent element (bismuth) to shift their Fermi energy towards the conduction band‐edge. With a controlled level of doping and thereby an appropriate shift of Fermi energy, a type‐II band‐alignment could be achieved at the perovskite/doped‐PbS interface, so that the charge‐separation becomes possible upon photogeneration in both the materials. In this work, conduction and valence band‐edges of the nanoparticles upon different extent of bismuth‐doping were monitored through differential tunnel conductance spectra, which have a correspondence to density of states of the semiconductors. The perovskite solar cells with the band‐engineered bismuth‐doped PbS‐layer could be seen to offer NIR activities due to presence of the nanoparticle layer. The NIR activities were in addition to normal responses of perovskite solar cells in the UV‐visible region. The overall power conversion efficiency hence augmented from 6.5 to 10.1% in the inverted planar structure.