Nanoporous Si - Organic composite photovoltaics

We report novel composite photovoltaics fabricated from nanoporous Si filled with Copper Phthalocyaninc (CuPC) and its derivatives, including discotic liquid crystal CuPC. Porous n-type Si (PSi) was prepared electrochemically (pore size 10-20 nm) and filled with CuPC solution by impregnation under pressure or spin casting (liquid crystal CuPC) onto a porous surface followed by heating to the temperature of the mesophase transition. For porous layer with the thickness more than 1500-2000 nm, the conversion efficiency was up to 3% under a tungsten lamp with solar filters (30 mW/cm²). The porous structure and pore filling were examined by SEM and XPS techniques. Photocurrent spectra of the CuPC-PSi cell demonstrate two bands that correspond to the absorbance of the protonated form of CuPC. A comparative analysis between CuPC and liquid crystal CuPC has been made and conclusions about possible mechanisms of charge transfer and transport are drawn. The solar cell optimization is discussed as well.