Impact of Relevant Gas Impurities on Thin-Film Silicon Solar Cell Performance

The influence of oxygen, nitrogen and carbon impurities on the performance of thin-film solar cells based on single junction a-Si:H absorber layer and tandem junction a-Si:H/μc-Si:H absorber layers deposited on industrial AKT® Gen 5 tool was studied. A series of intentionally contaminated complete solar cells were prepared by adding oxygen or nitrogen or methane (carbon precursor) during a Plasma-Enhanced Chemical Vapor Deposition (PECVD) process. It was found out that all the impurities have an ability to deteriorate the solar cells’ performance after a specific impurity concentration in hydrogen, called the critical level, has been exceeded. The contaminated solar cells were also studied by the means of Secondary Ion Mass Spectrometry (SIMS) in order to investigate the impurity concentration incorporated into the solar cells’ bulk so the impurity concentration in hydrogen could be matched to the incorporated impurity concentration in bulk.