Buried contact solar cells with innovative rear localised contacts

A new rear contacting scheme using low‐temperature processes to form localised contacts without the use of photolithography has been developed. It uses randomly nucleated, aluminium‐induced, localised regions of solid phase epitaxial growth ofp+silicon onto the rear surface of a wafer through a thick rear surface passivating oxide. This rear contacting technique has been applied on solar cells with front buried contacts and results have shown that a suitable ohmic contact to the rear can be formed through oxide as thick as 3000 Å and using only low temperature sintering below the eutectic temperature of silicon and aluminium. This low‐temperature sintering avoids the destruction of the interfacial oxide which has been shown to provide good surface passivation for the rear of the solar cells. Microscopic images indicate the possibility of formingp+rear contacts with aluminium‐induced crystallisation, but without requiring any additional deposition of silicon. The source of silicon for the latter appears to be from the reduction of the silicon dioxide by the aluminium.