In-depth analysis of chloride treatments for thin-film CdTe solar cells

CdTe thin-film solar cells are now the main industrially established alternative to silicon-based photovoltaics. These cells remain reliant on the so-called chloride activation step in order to achieve high conversion efficiencies. Here, by comparison of effective and ineffective chloride treatments, we show the main role of the chloride process to be the modification of grain boundaries through chlorine accumulation, which leads an increase in the carrier lifetime. It is also demonstrated that while improvements in fill factor and short circuit current may be achieved through use of the ineffective chlorides, or indeed simple air annealing, voltage improvement is linked directly to chlorine incorporation at the grain boundaries. This suggests that focus on improved or more controlled grain boundary treatments may provide a route to achieving higher cell voltages and thus efficiencies

Trachoma in South Africa

Trachoma remains the most common cause of preventable blindness in certain areas of the northern Transvaal region of South Africa. Results of epidemiological studies in the area indicate that trachoma is a familial disease with young children acting as the main source of infection within the family. Elderly women who have lived in these areas for long periods of time are at greater risk of blindness and impaired vision from the disease. Genital tract carriage of Chlamydia trachomatis is relatively infrequent in these trachoma-endemic areas and no evidence of eye-to-eye transmission of oculo-genital serotypes of C. trachomatis could be demonstrated.