High-efficiency silicon solar cells for car roofs

Silicon layers produced by HWCVD for a heterostructure solar cell.
© Fraunhofer IST, Falko Oldenburg
Silicon layers produced by HWCVD for a heterostructure solar cell.

Challenge 

Vehicle-integrated high-performance solar cells can only be used successfully if they meet the demanding requirements of automotive engineering. This is why high efficiency at low cost, visual appearance (color, impression) and the challenges of roof glazing in vehicles (e.g. hailstorm test, resistance to temperature and climatic changes) are of prime importance.

Solution 

During the project, highly efficient heterostructure solar cells were manufactured in which all the necessary silicon films were produced by the Fraunhofer IST using hot-wire CVD. Compared to the PECVD processes used previously, HWCVD represents a more cost-effective alternative for the production of functional films due to the simpler system concept, its high deposition rates (up to 7 nm/s) and the greatly improved gas utilization (> 80 %).

Added value 

The successful fabrication of SHJ solar cells by means of HCVD was demonstrated on large M2 wafer areas (156 x 156 mm²). Despite several interruptions in the process chain (wafer etching and cleaning, TCO deposition, metallization carried out by partners), cell efficiencies of 19.75 % were demonstrated on this wafer size. 

Project insights

Inline system with 7 compartments for the deposition of silicon and silicon nitride coatings with hot-wire chemical vapour deposition.
© Fraunhofer IST, Rainer Meier, BFF Wittmar
Inline system with 7 compartments for the deposition of silicon and silicon nitride coatings with hot-wire chemical vapour deposition.
Charge-carrier lifetime mapping of an M2 wafer after annealing in air at 220 °C for 30 minutes with an a-Si passivation layer thickness of 6 nm.
© Fraunhofer IST
Charge-carrier lifetime mapping of an M2 wafer after annealing in air at 220 °C for 30 minutes with an a-Si passivation layer thickness of 6 nm.

Funding reference

Bundesministerium für Wirtschaft und Energie

 

 

The project was funded by the German Federal Ministry for Economic Affairs and Energy (BMWi) under funding number 0324074A-H (PATOS).