1 research outputs found
Tandem Solar Cells from Solution-Processed CdTe and PbS Quantum Dots Using a ZnTe–ZnO Tunnel Junction
We developed a monolithic
CdTe–PbS tandem solar cell architecture in which both the CdTe
and PbS absorber layers are solution-processed from nanocrystal inks.
Due to their tunable nature, PbS quantum dots (QDs), with a controllable
band gap between 0.4 and ∼1.6 eV, are a promising candidate
for a bottom absorber layer in tandem photovoltaics. In the detailed
balance limit, the ideal configuration of a CdTe (<i>E</i><sub>g</sub> = 1.5 eV)–PbS tandem structure assumes infinite
thickness of the absorber layers and requires the PbS band gap to
be 0.75 eV to theoretically achieve a power conversion efficiency
(PCE) of 45%. However, modeling shows that by allowing the thickness
of the CdTe layer to vary, a tandem with efficiency over 40% is achievable
using bottom cell band gaps ranging from 0.68 and 1.16 eV. In a first
step toward developing this technology, we explore CdTe–PbS
tandem devices by developing a ZnTe–ZnO tunnel junction, which
appropriately combines the two subcells in series. We examine the
basic characteristics of the solar cells as a function of layer thickness
and bottom-cell band gap and demonstrate open-circuit voltages in
excess of 1.1 V with matched short circuit current density of 10 mA/cm<sup>2</sup> in prototype devices