An optical simulation of poly(3-hexylthiophene) (P3HT)/Si nanowire array (NWA) hybrid solar cells was investigated to evaluate the optical design requirements of the system by using finite-difference time-domain (FDTD) method. Steady improvement of light absorption was obtained with increased P3HT coating shell thickness from 0 to 80 nm on Si NWA. Further increasing the thickness caused dramatic decrease of the light absorption. Combined with the analysis of ultimate photocurrents, an optimum geometric structure with a coating P3HT thickness of 80 nm was proposed. At this structure, the hybrid solar cells show the most efficient light absorption. The optimization of the geometric structure and further understanding of the optical characteristics may contribute to the development for the practical experiment of the promising hybrid solar cells.

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A coupled three-dimensional optoelectrical simulation was used to evaluate the optical and electrical designs requirements for improving the efficiency of Si nanowire array (NWA)/Poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM) solar cells. Due to the addition of organic coating layers, better light absorptions are observed for the Si NWA/P3HT:PCBM structure at the wavelengths both below and above the absorption cutoff wavelengths of P3HT:PCBM. Optimized optical designs are obtained by maximizing the ultimate photocurrent under AM1.5G illumination. Furthermore, from the electrical simulation of the solar cell at optimized photo-absorption structure, the proposed Si NWA/P3HT:PCBM hybrid cell exhibits a promising character that is insensitive to exciton recombination at the optimized coating thickness of 80 nm. An efficiency of 9.4% can still be obtained even at high bimolecular recombination rates.