Design Of High Efficiency Organic Solar Cells Based On Two-Dimensional Arrayed Dielectric Nanospheres

We theoretically demonstrate a convex-concave organic solar cell based on two-dimensional arrayed silica (SiO 2 ) dielectric nanospheres loaded above the indium tin oxide (ITO) substrate, which can bring efficient light trapping in the active layer. In simulation, the PEDOT: PSS (buffer) and the PSBTBT:PC 71 BM (active) layers are conformal to that of the SiO 2 nanospheres, i.e., in the convex-concave shape. Fig. 1 shows that the absorption efficiency of light in the active layer increases over the whole wavelength range from 400 to 900nm when SiO 2 nanospheres with the diameter of 120nm are adopted, by comparison with that of the equivalent planar device (control). It also reflects that the enhancement factor of absorption for the patterned device with respect to the control is especially high at the edge of the absorption band of the active blend (e.g., around 100% at 820 nm). The integrated absorption efficiency of light in the active layer at normal incidence is up to 76.6%, increased by 21.6% as compared with that of the control (63.0%). Detailed investigations reveal that the excitation of photonic modes (i.e., the hybridization of cavity modes and Bloch modes) and plasmonic modes are responsible for the observed enhancement in absorption. In practice, SiO 2 nanospheres achieved with the low-cost solution process can form periodical array through the self-assembly method. The upper functional layers of the solar cells can then be structured conformably by the spin-coating process and thermal evaporation process. Experimentally, this proposal could also lengthen the interface between the active layer and the buffer layer, thereby favoring the charge collection. Compared with metal nanoparticles, the introduced dielectric nanospheres donu0027t suffer from the ohmic loss. This design contributes to the development of low cost solar cell devices.