F. Schmidhuber, C. Hebling Fraunhofer-Institute for Solar Energy Systems ISE Heidenhofstr. 2, 79110 Freiburg, Germany

Phone: +49 (0) 761/4588-5193, e-mail: helge. schmidhuber@ise. fraunhofer. de

Over 10 million Personal Digital Assistants (PDAs) and about 470 million cellular phones have been sold in the year 2003 ([Haines03], [Loding03]) and most of these devices use rechargeable batteries for the energy supply. The operation time of such devices can be increased if a solar module for charging the battery is integrated or if an external solar battery charger is used. With the today’s state of the art technology device integrated solar cells are interconnected either with tabs as in large standard modules, or they are contacted with the back on a printed circuit board (PCB). The front side contact is usually connected with a short tab on the plate. Partially the tabs are coloured black in order to give the solar module a uniform look. Contacting the solar cells to a PCB has the advantage that a mechanically very stable module is obtained. If one applies this interconnecting technology to high efficiency solar cells there is the disadvantage that by using the tabs the cell shading is increased. In this paper a novel method is presented, with which the shingle technology [Zhao97] and connection on a PCB are combined. One obtains an aesthetical, stable and nevertheless thin solar module, which is suitable for device integration.

A detailed description of the module concept is given and first measurements concerning the shingle technology, the connection and the encapsulation materials are shown. With the new module design it is possible to realise solar modules in a highly automated way with an efficiency between 18% and 20%.

Motivation

Today’s state of the art solar cells for device integration are interconnected either with small tabs as in large standard modules, or they are contacted with the back on a printed circuit board (PCB) and the front side contact is connected with a tab to the PCB. Partially the cell tabs are painted black, in order to give the solar module a uniform exterior. Contacting on a pCb has the advantage that depending upon choice of the PCB material a mechanically stable module is obtained and a packaging without a further backing material is possible. If the state of the art interconnecting technology is applied to high — efficient solar cells, it has the disadvantage that by the use of cell tabs the cell shading is increased.

The shingle technology for solar cells is described in [Zhao97] and [SCHMIDHUBER01a]. In this case the inactive cell part under the bus bar is covered by the active part of the next solar cell. The shading of the solar cells is reduced thereby and the module efficiency is increased.

In this paper a method is presented, in which the shingle technology and the interconnection on a PCB are combined. One receives an aesthetically looking, stable and nevertheless thin solar module, which is suitable for device integration. This new module concept is also very easy to produce because the finishing technology for surface mounted devices (SMD) can partially be used.