Highly Efficient PEDOT:PSS/Silicon Hybrid Solar Cells via Effective Surface Microengineering of Low-Cost Solar-Grade Silicon Wafers

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 similar to 9.70% (similar to 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.