A reverse silicon solar cell

Abstract

In order to increase the efficiency of large-area solar cells made from thin (less than or equal to 200 μm) crystal wafers, without eliminating the thick film process sequence, an innovative back junction cell with a front contact grid on the lit side was developed. The major advantages of the reverse cell over the conventional cell are as follows:

• 1.

  (1) the reverse cell is suitable for the collection of long-wavelength light reflected on the back surface and at the same time of the short wavelengths owing to the opportunity of forming a shallow front surface p + layer without the risk of leakages from the contact metallization.

• 2.

  (2) the series resistance of the back and front contacts can be greatly reduced.

In this work we carried out a process sequence for reverse cell production: up to now our best fill factor was 78% which is probably the highest value obtained using thick film technology.

In addition, using numerical modelling, we analysed the spectral responsivity, the short-circuit current and the dependence of the efficiency on the front surface field depth. The behaviour of the short-circuit current with increasing lifetime was also investigated.