PbBi4S7: A New Infrared Solar Absorber Material Exhibiting High Photocurrents

Abstract

We report a new absorber material for quantum dot-sensitized solar cells (QDSCs). PbBi4S7 nanocrystals (NCs) have been synthesized using a two-stage successive ionic layer adsorption and reaction technique. The synthesized NCs have an average size of ∼ 14 nm and an optical bandgap of ∼ 1.3 eV. PbBi4S7 QDSCs were fabricated from the synthesized NCs for the first time. The best cell, fabricated with an Au counter electrode and a polysulfide electrolyte, yielded a short-circuit current density Jsc of 4.84 mA/cm2, an open-circuit voltage Voc of 0.12 V and an efficiency η of 1.26% under the reduced light intensity of 14% sun. When the polysulfide electrolyte was replaced by a cobalt electrolyte with a lower redox level, the Voc increased to 0.37 V and the η increased to 1.48%. The EQE spectrum covered the visible and near-infrared ranges of 300–1000 nm with a maximum EQE of 63.4% at λ = 450 nm. The relatively large photocurrent of Jsc ∼ 16 mA/cm2, which results from the broad absorption band, is an attractive property for a solar absorber material. This work demonstrates that PbBi4S7 shows potential as a solar material that could generate large photocurrents.