XIS: A low-current, high-voltage back-junction back-contact photovoltaic device

Abstract

In this paper we present a low-current, highvoltage back-junction back-contact integrated photovoltaic concept and experimental results of such a device, consisting of strip cells: narrow solar cells instead of conventional square cells. The concept is demonstrated by the successful transformation of a completely finished IBC cell into a XIS (Crystalline SiliconInterconnected Strips) device, leading to a V oc of 8.5 V for a series connection of 14 strip cells. For cell separation, different grooving methods were evaluated with respect to their effect on the quality of the groove surface. The effect of the surface passivation in the grooves, which is regarded as a critical parameter, on the XIS device was simulated to gain a better understanding of the processing requirements.

High voltage MWT module with improved shadow performance

“…3. The greater effect on the short circuit current is to be expected and is in line with results reported elsewhere [3].…”

“…These products have a very specific market and are not intended for large area, high power installations. At the other end of the spectrum there are more exotic examples of high voltage module technologies including Sliver [2] and XIS [3], as well as many thin film technologies.…”

Edge isolation of solar cells using laser doping

“…Edge recombination can be a particularly significant parasitic loss mechanism in small-area solar cells, such as laboratory-scale high efficiency solar cells, concentrator solar cells, and novel devices which rely on small area solar cells to be interconnected for low current, high voltage applications [13,14], as the losses are accentuated due to the large perimeter to area ratio present in these types of structures [15]. Several methods have been used to perform edge isolation in a manner to minimise the amount of recombination at the edge region, typically introducing an isolation groove around the edge [9,16] or partially cutting the cell out of the host wafer [17] at the front end of processing, such that the groove or cut face can be damage etched and well-passivated with a thermally grown oxide.…”

“…Several methods have been used to perform edge isolation in a manner to minimise the amount of recombination at the edge region, typically introducing an isolation groove around the edge [9,16] or partially cutting the cell out of the host wafer [17] at the front end of processing, such that the groove or cut face can be damage etched and well-passivated with a thermally grown oxide. Water-jet guided lasers have also been used [14,18] as an alternative to conventional laser edge isolation to reduce the damage induced by laser heat. Other methods have involved leaving a gap between the active area of the solar cell and the edge of the wafer with the use of an aperture to shade the edges [7,19].…”