S. Narayanan

Plasma-texturization for multicrystalline silicon solar cells

Multicrystalline Si (mc-Si) cells have not benefited from the cost-effective wet-chemical texturing processes that reduce front surface reflectance on single-crystal wafers. The authors developed a maskless plasma texturing technique for mc-Si cells using reactive ion etching (RIE) that results in much higher cell performance than that of standard untextured cells. Elimination of plasma damage has been achieved while reducing front reflectance to extremely low levels. Internal quantum efficiencies higher than those on planar and wet-textured cells have been obtained, boosting cell currents and efficiencies by up to 11% on monocrystalline Si and 2.5% on multicrystalline Si cells.

RIE-Texturing of Industrial Multicrystalline Silicon Solar Cells

We developed a maskless plasma texturing technique for multicrystalline Si (mc-Si) cells using Reactive Ion Etching (RIE) that results in higher cell performance than that of standard untextured cells. Elimination of plasma damage has been achieved while keeping front reflectance to low levels. Internal quantum efficiencies higher than those on planar and wet-textured cells have been obtained, boosting cell currents and efficiencies by up to 6% on tricrystalline Si cells.

Greater Than 16% Efficient Screen Printed Solar Cells on 115-170 μm Thick Cast Multicrystalline Silicon

In this paper we report on the impact of mc-Si wafer thickness on efficiency. We have obtained 16.8%, 16.4%, 16.2% and 15.7% efficient screen printed 4 cm2 solar cells on 280 mum, 170 mum, 140 mum and 115 mum thick cast mc-Si respectively. Analysis of these cells showed that the efficiency of the 115 mum thick cell is limited by a BSRV of 750 cm/s, FSRV of 120,000 cm/s and a BSR of 67%. A module manufacturing cost model for a 25 MW plant was used to demonstrate that 15.7% efficient cells on 115 mum thick wafers are more cost effective than 16.8% cells on 280 mum wafers. The module manufacturing cost reduced from

RIE-texturing of industrial multicrystalline silicon solar cells

1.82/W to

Interactions Between Metals and Different Grain Boundary Types and Their Impact on Multicrystalline Silicon Device Performance

1.63/W when the wafer thickness was reduced from 280 mum (efficiency 16.8%) to 115 mum (efficiency 15.7%). A roadmap is developed for 115 mum thick wafers to demonstrate how cell efficiency can be increased to greater than 18% resulting in a module cost of less than

Investigation of the Effect of Resistivity and Thickness on the Performance of Cast Multicrystalline Silicon Solar Cells

1.40/W

Commercialization of a silicon nitride co-fire through (SINCOFT) process for manufacturing high efficiency mono-crystalline silicon solar cells

We developed a maskless plasma texturing technique for multicrystalline Si (mc-Si) cells using reactive ion etching (RIE) that results in higher cell performance than that of standard untextured cells. Elimination of plasma damage has been achieved while keeping front reflectance to low levels. Internal quantum efficiencies higher than those on planar and wet-textured cells have been obtained, boosting cell currents and efficiencies by up to 6% on tricrystalline Si cells.

Photovoltaic Cell and Production Thereof

The mechanical and electrical properties of polycrystalline solids, such as metals, ceramics, and photovoltaic-grade multicrystalline silicon (mc-Si), are strongly regulated by the interactions between impurities and grain boundaries. In this broader context, we combine synchrotron-based X-ray fluorescence microscopy (mu-XRF), SEM-based electron back-scatter diffraction (EBSD), and conventional techniques to correlate metal precipitation behavior with grain boundary character (type), electrical activity, and microstructure in commercial multicrystalline silicon (mc-Si) materials. It is directly observed that metals tend to form precipitates selectively at higher-Sigma coincidence site lattice (CSL) boundaries and non-CSL boundaries, while largely avoiding precipitation at Sigma3 boundaries, and to a lesser extent, Sigma9. The electrical impacts of this behavior differ, depending on surrounding intragranular quality. A discussion of mc-Si grain boundary engineering ensues

Improved photovoltaic cell and method of production thereof

A low resistivity of 0.2-0.3 Omegacm has been shown to be optimum for high quality single crystal silicon for solar cells. However, for lower quality cast mc-Si, this optimum resistivity increases owing to a dopant-defect interaction, which reduces the bulk lifetime at lower resistivities. In this study, solar cells fabricated on 225 mum thick cast multicrystalline silicon wafers showed very little or no enhancement in efficiency with the decrease in resistivity. However, Voc enhancement was observed for the lower resistivity cells despite significantly lower bulk lifetimes compared to higher resistivity cells. After gettering (during P diffusion) and hydrogenation (from SiNx) steps used in cell fabrication, the bulk lifetime in 225 mum thick wafers from the middle of the ingot decreased from 253 mus to 135 mus when the resistivity was lowered from 1.5 Omegacm to 0.6 Omegacm. This paper shows that solar cells fabricated on 175 mum thick, 1.5 Omegacm, wafers showed no appreciable loss in the cell performance when compared to the 225 mum thick cells, consistent with PC1D modeling