Improved open circuit voltage using metal mediated epitaxial growth in thyristor structure solar cells

Abstract

Most presently manufactured bulk photovoltaic devices suffer from poor rear surface recombination velocities which limit the achievable efficiencies. In order to overcome this efficiency limitation, an innovative approach to redesigning the rear contact has been sought. The Buried Contact Solar Cell (BCSC) has been chosen as the basis for this study as this technology has been proven to be superior in performance to other commercially available bulk technologies. The new rear contacting scheme has been devised with improved experimental devices demonstrated. It utilises a process known as Metal Mediated Epitaxial Growth (MMEG) to achieve an improved Back Surface Field (BSF). This device design can also take advantage of the thyristor structure by utilising the p + region formed by MMEG in conjunction with the n-p-n structure unavoidably produced during most manufacturing processes. Results indicate that superior rear surface passivation can be achieved using this process and design. Higher open circuit voltages in the vicinity of 30-40 m V have been achieved relative to the conventional BCSC, indicating that higher efficiency devices are possible.