Dopant-free random inverted nanopyramid ultrathin c-Si solar cell via low work function metal modified ITO and TiO2 electron transporting layer

Ultrathin c-Si solar cells with light trapping nanostructures attract tremendous research interest for their flexibility and high specific power density. However, the performance of the ultrathin c-Si solar cell is limited by a big light absorption loss due to the reduced thickness. Here, we report a novel ultrathin c-Si solar cell through the direct deposition of TiO2 electron transporting layer and indium tin oxide (ITO) electrode modified with ultrathin low workfunction (WF) metal subsequently onto random inverted nanopyramids (INPs) texture. The random INPs are fabricated through the well-known two-step Ag assisted chemical etching method followed by a post nanostructure rebuilding process. The TiO2 thickness, deposition temperature and metal layer thickness are changed to optimize cell performance. With the optimized parameters, a high short-current density (Jsc) (30.66 mA/cm2) and energy-conversion efficiency (11.36%) are achieved on random INPs based 45 μm ultrathin c-Si solar cell by choosing 2 nm Mg layer as the modifying ultrathin metal layer, which are 37.65% and 36.4% respectively higher than that in planar one. All the findings not only offer additional insight into the mechanism of TiO2 electron transporting layer based ultrathin c-Si solar cell but also introduce a promising new approach for next-generation cost effective flexible photovoltaics.