Back contact solar panels: combining high power and aesthetics

In addition to green-field and residential applications, these technologies also offer unique opportunities for the urban environment and the transport sector. These include all-black panels, shadow-tolerant panels, various panel shapes and dimensions and patterned or single-colour appearances.

The trend of continuously higher power conversion in industrial PV panels is due to global and long term research by company laboratories and R&D institutes, including TNO. Higher module power conversion efficiency is one of the best drivers for lower cost electricity production and more competitive PV. A high module efficiency is also particularly relevant for distributed generation in the urban environments of densely populated and build-up regions and countries, where the impact of power generation will be directly limited by the available area.

RECORD EFFICIENCY

To support these developments, TNO develops module technology for all back contact c-Si solar cells, including metal wrap-through (MWT) and interdigitated back-contact (IBC) concepts. Back contact cells have the potential to reach the highest conversion efficiencies for single-junction c-Si solar cells. TNO technology offers the opportunity to connect these cells together with no or very limited efficiency losses and high reliability. TNO and her partners have developed a combined interconnection and lamination concept based on conductive back sheet foil (like a printed circuit board for PV modules) and back contact solar cells.

Free design possibilities of BACK contact

The efficiency advantages of conductive back sheet module technology are very relevant for the residential market as well as special applications of PV; in all situations where the highest power output in a small area is needed. In addition, the conductive back sheet foil offers a large degree of freedom in the design of the cell interconnection, compared to the very rigid rectangular patterns of stringed solar cells. Conductive back contact foil allows for variation in (cut) cell sizes, cell-cell distances, orientation of the cells, and better performance when the PV element can not be optimally oriented toward the sun (like on the side of a building). In particular on the European market, there is an increasing demand for variation in the supply of PV panels for new applications: one size no longer fits all. Back contact foil modules can be easily manufactured in all these variants.

The TNO toolbox, in particular the conductive back sheet cell-cell interconnection, thus offers unique opportunities for new applications and appearances in the urban environment. This has been demonstrated in a large portfolio of prototype and pilot-production modules, featuring all-black appearance, shadow tolerance, patterns and colouring, extremely thin cells (<100 micron) or almost arbitrary shapes and dimensions.

EXPERTISE PORTFOLIO

TNO has developed in the last 10-15 years an extended technology and expertise portfolio. In collaboration with industrial partners like materials and equipment suppliers and manufacturers of solar cells and modules, the technology has been further developed and is already used for large scale manufacturing of rectangular modules for residential applications. Now TNO is focused on expanding the applicability for the urban environment and other applications.

TNO can support your research and development of back contact solar panels

• Cell processing and metallisation pattern optimalisation
• Unique interconnection technology to integrate back contact cells in PV panels including processing techniques and equipment
• Application of existing and new materials for solar panels for conventional and novel applications
• Building prototypes, in particular, different sizes, shapes, 3D curved and light weight
• Characterisation and reliability testing of solar panels