Two-dimensional photonic crystal arrays for polymer:fullerene solar cells

摘要

We report the application of two-dimensional (2D) photonic crystal (PC) array substrates for polymer:fullerene solar cells of which the active layer is made with blended films of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The 2D PC array substrates were fabricated by employing a nanosphere lithography technique. Two different hole depths (200 and 300nm) were introduced for the 2D PC arrays to examine the hole depth effect on the light harvesting (trapping). The optical effect by the 2D PC arrays was investigated by the measurement of optical transmittance either in the direction normal to the substrate (direct transmittance) or in all directions (integrated transmittance). The results showed that the integrated transmittance was higher for the 2D PC array substrates than the conventional planar substrate at the wavelengths of ca.400nm, even though the direct transmittance of 2D PC array substrates was much lower over the entire visible light range. The short circuit current density (J _(SC)) was higher for the device with the 2D PC array (200nm hole depth) than the reference device. However, the device with the 2D PC array (300nm hole depth) showed a slightly lower J _(SC) value at a high light intensity in spite of its light harvesting effect proven at a lower light intensity.