Profile and interface control of hybrid organic-silicon nanorod solar cells

Hybrid organic-silicon solar cells are promising candidates for next-generation photovoltaics due to their low fabrication cost and scalable roll-to-roll processes. However, the power conversion efficiency (PCE) cannot compete with those of traditional silicon solar cells yet mostly due to surface reflection and interface recombination losses. In this work, we investigate the sidewall profile and interface defects of silicon nanorod templates, fabricated by means of polystyrene lithography, followed by metal-assisted chemical etch (MACE), for hybrid photovoltaics. The control of nanorod sidewall profile is important to organic surface coverage, as well as optical absorption for thin-silicon substrates, whereas the control of interface defects is important to boost the open-circuit voltage of hybrid devices. We systematically compared the optical and electrical characteristics of hybrid organic- silicon nanorod (Si NR) devices made with different noble metal etching catalysts: gold (Au) and silver (Ag), which result in different surface morphologies. The preliminary results show that Si NRs made of Ag catalysts have lower interface defects than those of Au catalysts. After passivated by 10nm-Al₂O₃, the minority carrier lifetime is 157 μsec (Ag) versus 29 μsec (Au). Moreover, a PCE of 11.9% is achieved with the hybrid solar cells using Ag catalysts without any post-etching surface treatment, where the short-circuit current is as high as >34 mA/cm₂ enhanced by the nearly periodical pillar arrangement. The Si NR template made with Au catalysts requires further damage removal etch (DRE), which also lead to a high PCE of 11.37% and Jsc of ~ 34 mA/cm₂. Currently optimization of device structure and fabrication technique is still in process and more experimental and simulation data will be presented.