Silicon Nanorod / Quantum Dot / C-Si Composite High Efficiency Solar Cell

In all different kinds of solar cells nowadays, crystalline Si (c-Si) based solar cell takes the lead,due to its earth abundant, mature in large scale fabrication and high efficiency. In recent years, theresearches in power efficiency conversion (PCE) improvement in c-Si are mostly focusing on thesurface improvement of the cells. In this study, one-demensional sub-wavelength Si nanostructurewas capped with different kinds of quantum dots (QDs), to form the Si/QDs composited structure.Afterwards, we studied the J-V character of the composited solar cells and analyzed the mechanismof the improved PCE.This article is based on the former researches, we carefully studies the characteristics ofone-demensional sub-wavelength Si nanostructure and its composite with different kinds of QDsafterwards. The PCE enhancement of the composited solar cell included two aspects. Firstly, we tookon an easy step to fabricate the one-demensional Si nanostructure on Si based solar cells. The lengthof the Si nanostructure was ranging from20-250nm. The absorption enhanced with the increased ofSi nanostructure length, especially among the region of250-550nm. On the contrary, the minoritycarrier lifetime decreased rapidly as the length increase of Si nanostructure. We finally found theoptimum Si nanostructure length by studying the J-V characters of each sample. Secondly, QDs asPbS、CdS、Ag2S、Sb2S3were synthesized by means of High Temperature Pyrolysis, Chemical VaporDeposition（CVD) and Chemical Bath Deposition（CBD), with an average diameter of2-3nm. Thecolloid QDs were capped onto the Si nanostructure by spin coating, sintering with the protection ofN2, thus get the Si/QDs composited structure. After measuring the J-V characters, the compositedsolar cell displayed3-6%enhancement in open circuit voltage,19-27%improvement in short circuitcurrent，and21-30%increase in PCE, comparing with the bare Si solar cell. One-demensionalsub-wavelength Si nanostructure efficiently improved the light absorption. QDs layer on hand actedas passivate layer, on the other had the ability to slow down hot carriers recombination. Moreover,with proper down conversion properties, the QDs could help to improve the utility of wholespectrum.