Quantification of Valleys of Randomly Textured Substrates as a Function of Opening Angle: Correlation to the Defect Density in Intrinsic nc-Si:H

• Published in: ACS applied materials & interfaces Vol. 8; no. 32; pp. 20660 - 20666
• Main Authors: Kim, Do Yun, Hänni, Simon, Schüttauf, Jan-Willem, van Swaaij, René A. C. M. M, Zeman, Miro
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 17.08.2016
• Subjects: electrical properties; light scattering; nanocrystals; photovoltaic cells; silicon; zinc oxide; opening angle; nc-Si:H; morphology; simulation; defect density; defective valleys; solar cell
• DOI: 10.1021/acsami.6b03995
• ISSN: 1944-8244; 1944-8252

Optical and electrical properties of hydrogenated nanocrystalline silicon (nc-Si:H) solar cells are strongly influenced by the morphology of underlying substrates. By texturing the substrates, the photogenerated current of nc-Si:H solar cells can increase due to enhanced light scattering. These textured substrates are, however, often incompatible with defect-less nc-Si:H growth resulting in lower V oc and FF. In this study we investigate the correlation between the substrate morphology, the nc-Si:H solar-cell performance, and the defect density in the intrinsic layer of the solar cells (i-nc-Si:H). Statistical surface parameters representing the substrate morphology do not show a strong correlation with the solar-cell parameters. Thus, we first quantify the line density of potentially defective valleys of randomly textured ZnO substrates where the opening angle is smaller than 130° (ρ<130). This ρ<130 is subsequently compared with the solar-cell performance and the defect density of i-nc-Si:H (ρdefect), which is obtained by fitting external photovoltaic parameters from experimental results and simulations. We confirm that when ρ<130 increases the V oc and FF significantly drops. It is also observed that ρdefect increases following a power law dependence of ρ<130. This result is attributed to more frequently formed defective regions for substrates having higher ρ<130.