Abstract:
CZTSSe solar cells are considered to be potential and cost-effective alternative solutions to mature
photovoltaic technology for meeting future energy demands. However, the current performance of
CZTSSe solar cells is limited due to their high voltage deficit. The comparison of figure-of-merits of the
two technologies show that CZTSSe has 62% lower open circuit voltage compared to that of 35% for
CIGS, with respect to their associated band gaps. Efficient charge separation and extraction at the
absorber–buffer (p–n) junction is paramount for mitigating the voltage loss and achieve high photoconversion
efficiency. The rapid progress for achieving high deliverables in CZTSSe is impeded by
interface recombination, which is a consequence of poor-quality p–n junction. The inherent association
of CZTSSe with secondary phases and defects due to narrow phase stability plays an unfavorable role in
producing a good quality interface. The high density of interface defects, unfavorable band alignment,
and structural inhomogeneities across the interface are some of the leading causes that nurture interface
dominant recombination pathways. These interface-related concerns have drawn the scientific
community towards interface engineering and modification of the interface to bring closer performance
parity between CZTSSe and matured CIGS solar cell technology. Several approaches have attempted to
develop favorable interface features that facilitate improved device performance. This work addresses
the critical aspects of interface engineering of the absorber–buffer heterojunction in CZTSSe solar cells
and the importance of tools that are essential to identify and eradicate the root causes of low efficiency.
