Effects of acid-treated silicon nanowires on hybrid solar cells performance

Abstract : We demonstrate the efficiency improvement of hybrid solar cells based on silicon nanowires (SiNWs) and organic materials. This progress is readily achieved by acid treatments of SiNWs. Tin (Sn) catalyzed SiNWs contain residual Sn and Sn oxide drops on their top which are deleterious for a solar cell performance. Removal of this Sn and Sn oxide contamination is performed with hydrochloric acid. X-ray photoelectron spectroscopy measurement verified that the amount of Sn and Sn oxide on SiNWs array is decreased according to the immersing time. This brings open-circuit voltage and shunt resistance increase thus the hybrid solar cell performance is improved. Light intensity dependent open-circuit voltage clearly reveals that this efficiency improvement results from a reduced trap-assisted recombination through Sn and Sn oxide. In addition to the residual catalysts removal, native oxide removal by hydrofluoric acid also considerably contributes to further improvement in terms of short-circuit current and fill factor. Clearly, the improvement of SiNWs quality is essential for an optimization of hybrid solar cell performance.