posted on 2017-05-10, 00:00authored bySongping Luo, Miri Kazes, Hong Lin, Dan Oron
Colloidal
CdSe nanoplatelets (NPLs) deposited on TiO2 and overcoated
by ZnS were explored as light absorbers in semiconductor-sensitized
solar cells (SSSCs). Significant red shifts of both absorption and
steady-state photoluminescence (PL) along with rapid PL quenching
suggest a type II band alignment at the interface of the CdSe NPL
and the ZnS barrier layer grown on the NPL layer, as confirmed by
energy band measurements. The considerable red shift leads to enhanced
spectral absorption coverage. Cell characterization shows an increased
open-circuit voltage of 664 mV using a polysulfide electrolyte, which
can be attributed to a photoinduced dipole effect created by the spatial
charge separation across the nanoplatelet sensitizers. The observed
short-circuit current density of 11.14 mA cm–2 approaches
the maximal theoretical current density for this choice of absorber,
yielding an internal quantum efficiency of close to 100%, a clear
signature of excellent charge transport and collection yields. With
their steep absorption onset and negligible inhomogeneous broadening,
NPL-based SSSCs are intriguing candidates for future high-voltage
sensitized cells.