The influence of porous silicon coating on silicon solar cells with different emitter thicknesses

The influence of the emitter thickness on the photovoltaic properties of monocrystalline silicon solar cells with porous silicon was investigated. The measurements were carried out on n+p silicon junction whose emitter depth was varied between 0.5 and 2.2 μm. A thin porous silicon layer (PSL), less than 100 nm, was formed on the n+ emitter. The electrical properties of the samples with PS were improved with decrease of the n+p junction depth. Our results demonstrate short-circuit current values of about 35–37 mA/cm2 using n+ region with 0.5 μm depth. The observed increase of the short-circuit current for samples with PS and thin emitter could be explained not only by the reduction of the reflection loss and surface recombination but also by the additional photogenerated carriers within the PSL. This assumption was confirmed by numerical modeling. The spectral response measurements were performed at a wavelength range of 0.4–1.1 μm. The relative spectral response showed a significant increase in the quantum efficiency of shorter wavelengths of 400–500 nm as a result of the PS coating. The obtained results point out that it would be possible to prepare a solar cell with 19–20% efficiency by the proposed simple technology.