Nanostructured surfaces

Investigation of nanoporous silicon on the frontal surface of solar cells by mass spectroscopy
Yerokhov V.Yu., Druzhinin A.A., Nichkalo S.I.
Department of Semiconductor Electronics, Lviv Polytechnic National University, 
S. Bandera Str., 12, Lviv-79013, Ukraine
E-mail: v.yerokhov@gmail.com
When using nanoporous silicon as a texture and anti-reflective coating, the nanoporous layer is formed directly on the silicon surface of the front layer of solar cells (SC). Along with blooming, it must also provide passivation of the SC surface. However, research in this area has shown that the passivating properties of porous silicon are insufficient to minimize surface recombination [1]. Partial improvement of the passivating properties of nanoporous silicon was achieved by thermal and anodic oxidation of the porous layer, as well as by plasma spraying on its surface of silicon nitride [2]. However, none of these methods allowed to achieve the required level of surface passivation and its stabilization over time.
To obtain frontal functional nanolayers of SC, an in-depth analysis of existing models of porous silicon was performed. The selected models are the most effective for creating an effective and cost-effective coating based on nanoporous silicon and the most adapted to the processes of creating silicon SC.
A more effective method of improving the passivating properties of porous silicon can be its electrochemical hydrogenation in hydrogen-enriched electrolytes. This treatment can be achieved by efficient passivation of hydrogen-broken bonds at the interface between porous silicon/monocrystalline or polycrystalline silicon.
Mass spectroscopy was used to study the frontal surface of the SC. We also studied the surface appearance of multicrystalline silicon samples before and after hydrogenation in hydrogen and in an electrolyte based on hydrofluoric acid, both in the spectra of secondary ions and in the image of the distribution of elements on the surface (ion microprobe mode and mass spectral ion microscope).

1.	Yoo J., Yu G., Yi J. Black surface structures for crystalline silicon solar cells. // Materials Science and Engineering B.– 2009.– 159-160.– P. 333–337. 
2.	Fang W., Changshui C., Huili H. Analysis of sunlight loss for femtosecond laser microstructed silicon and its solar cell efficiency // Applied Physics A: Materials Science and Processing. – 2011. - 103(4). - P 977-982.