Potential of quasi-inverted pyramid with both efficient light trapping and sufficient wettability for ultrathin c-Si/PEDOT:PSS hybrid solar cells

In this paper, a simple and cost-effective wet chemical method is presented to form quasi-inverted pyramids (QIP) on ultrathin c-Si for efficient light trapping and sufficient wettability. The QIP is fabricated by a well-known two-step Ag assisted chemical etching method followed by a post nanostructure rebuilding (NSR) process. The variation of [Ag+] realizes the modulation of QIP size from sub-micro scale to micro scale. The comparable average absorptance value of 50 pm c-Si with double-sided QIP fabricated under 0.5 mM [Ag+] (QIP-50) to that of 182 pm c-Si with double-sided conventional micro-scale pyramid in the spectral range of 300 - 1100 nm demonstrates an over 3.6-fold reduction in material usage. In comparison with nanopores-structured light-trapping configuration, the QIP-50 possesses much smaller specific surface area of similar to 2.39, which alleviates the surface recombination losses. After wet oxidation treatment, the water contact angle (WCA) of QIP-50 (35.73 degrees) can achieve a comparable value to that of wet oxidized polished wafer (33.30 degrees), demonstrating sufficient wettability of the QIP for high efficiency ultrathin c-Si/PEDOT:PSS hybrid solar cells. The finding of QIP with both efficient light trapping and superior wettability provides a new opportunity to improve the performance of ultrathin c-Si/PEDOT:PSS hybrid solar cells with a simple process at low cost.