Abstract
SiNW/PEDOT:PSS hybrid solar cells are fabricated on 10.6-μm-thick crystalline Si thin films. Cells with Si nanowires (SiNWs) of different lengths fabricated using the metal-catalyzed electroless etching (MCEE) technique have been investigated. A surface treatment process using oxygen plasma has been applied to improve the surface quality of the SiNWs, and the optimized cell with 0.7-μm-long SiNWs achieved a power conversion efficiency (PCE) of 7.83 %. The surface treatment process is found to remove surface defects and passivate the SiNWs and substantially improve the average open circuit voltage from 0.461 to 0.562 V for the optimized cell. The light harvesting capability of the SiNWs has also been investigated theoretically using optical simulation. It is found that the inherent randomness of the MCEE SiNWs, in terms of their diameter and spacing, accounts for the excellent light harvesting capability. In comparison, periodic SiNWs of comparable dimensions have been shown to exhibit much poorer trapping and absorption of light.
Highlights
In recent years, extensive research has been devoted towards rendering solar energy more cost competitive to be a viable energy source
It is observed that PEDOT:PSS forms a continuous canopy on top of the Si nanowires (SiNWs) instead of penetrating into the SiNW gaps, attributed to its long polymer chain [16]
The better power conversion efficiency (PCE) is mainly due to the improvement in Voc across all the samples, as well as higher Jsc and FF for samples with longer SiNWs. This is attributed to the surface treatment that resulted in the removal of impurity particles and defects on the SiNW surface, which is crucial for longer SiNWs due to their large surface area
Summary
Extensive research has been devoted towards rendering solar energy more cost competitive to be a viable energy source. SiNWs fabricated by the low cost solution-based metal-catalyzed electroless etching (MCEE) technique have been combined with organic semiconductors to form hybrid solar cells [4, 5]. Such cells present a very cost-effective option due to their simple structure, coupled with the solution-based, low temperature and large area fabrication process. A promising power conversion efficiency (PCE) of 13.01 % has been reported for hybrid solar cells based on SiNWs and poly(3,4-ethylene-dioxythiophene):polystyrenesulfonate (PEDOT:PSS) [6].
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