A novel hierarchical structure integrating ZnO‐nanowire arrays on Si micropyramids is reported as an effective antireflection layer for improving the solar‐cell conversion efficiency. This structure displays a broadband reflection suppression with an average weighted reflectance of 3.2%. Solar cells based on the hierarchal structure show a high conversion efficiency of 16.0%, as well as a superior self‐cleaning property.

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A boron diffusion process using boric acid as a low cost, nontoxic spin-on source is introduced. Using dilute solutions of boric acid, sheet resistances ranging from 20 to 200Ω/◻ were achieved, along with saturation current densities as low as 85fA/cm2 . These results indicate that boric acid is a suitable source for forming both normalp+ emitters and back surface fields for high efficiency n- and p-type solar cells. The degradation of the minority carrier bulk lifetime, which is a common efficiency-limiting characteristic of low cost boron sources, was also minimized through the use of a high purity boric acid source. The ability to achieve low sheet resistances, high bulk lifetimes and low saturation current densities with boric acid were exploited to achieve a 19.7% efficient screen printed solar cell exhibiting a bulk lifetime 400μs .

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Two-dimensional numerical simulations were performed to derive design rules for low-cost, high-efficiency interdigitated back contact (IBC) solar cells on a low-cost substrate. The IBC solar cells were designed to be fabricated using either the conventional screen printing or photolithography metallization processes. Bulk lifetime, bulk resistivity, contact spacing (pitch), contact opening width, recombination in the gap between the p + BSF and n + emitter, and the ratio of emitter width to pitch have been used as key variables in the simulations. It is found that short circuit current density (Jsc) is not only a strong function of the bulk lifetime but also the emitter coverage of the rear surface. Fill factor (FF) decreases as the emitter coverage increases because the majority carriers need to travel a longer distance through the substrate for longer emitter width. The simulated IBC results were compared with those for conventional screen printed solar cells. It was found that the IBC solar cell outperforms the screen printed (SP) solar cell when the bulk lifetime is above 50 μs due to higher Voc and Jsc, which suggests that higher performance can be realized on low-cost substrates with the IBC structure.