The organic carrier-selective layer,
poly(3,4-ethylenedioxythiophene):poly(styrene
sulfonate) (PEDOT:PSS) coated on Si wafers, has attracted a lot of
attention toward the development of low-cost and efficient hybrid
solar cells (HSCs). Here, highly efficient PEDOT:PSS/Si HSCs are reported
via an effective surface microengineering of the as-cut, low-cost
solar-grade thin Si wafers, an aspect rarely addressed before, by
a simple one-step aqueous KOH process. The influence of surface microstructuring
on their light harvesting properties, polymer/Si junction formation,
and photovoltaic (PV) performance of the PEDOT:PSS/Si HSCs are investigated.
The simple one-step process under the optimized processing conditions
reduces the weighted surface reflectivity from >35 to <9% in
a
broad spectral range in addition to removing the surface saw damages
of the wafers completely. The combined effect in turn improves the
PEDOT:PSS/Si interface (junction) property, leading to a highly efficient
PEDOT:PSS/Si HSC even in its simplest possible device structure. Moreover,
the antireflective and surface passivation properties of the PEDOT:PSS
layer for the microstructured Si surfaces are also demonstrated. The
optimized microsurface and cell processing conditions resulted in
the HSCs with a photoconversion efficiency >12.25%, which is absolute
∼9.70% (∼5 folds) higher when compared to that on starting
non-structured Si wafers. The results are further supported by detailed
dark J–V characteristics
and quantum efficiency analysis of the devices. The study establishes
that microengineering of the commercial as-cut Si wafers removes the
surface damages on both sides which if not addressed properly cause
very high surface recombination losses and have a detrimental effect
on the polymer/Si junction and hence the PV performances. The study
paves the way to develop simple yet efficient HSCs on such economic
solar-grade Si wafers commonly used for the conventional Si solar
cells.
