Fabrication and analysis of record high 18.2%25 efficient solar cellson multicrystalline silicon material

• Published in: IEEE electron device letters Vol. 17; no. 8; pp. 401 - 403
• Main Authors: Rohatgi, A, Narasimha, S, Kamra, S, Khattak, C P
• Format: Journal Article
• Language: English
• Published: 01.08.1996
• ISSN: 0741-3106
• DOI: 10.1109/55.511588

Solar cell efficiencies of 18.2% (1 cm(2) areas) have been achieved using a process sequence which involves impurity gettering on 0.65 Omicron-cm multicrystalline silicon (mc-Si) grown by the heat exchanger method (HEM). This represents the highest reported solar cell efficiency on mc-Si to date. Photoconductive decay (PCD) measurements were used to monitor the lifetime in control samples which underwent the same process sequence as solar cells. PCD analysis reveals that HEM mc-Si material with an average as-grown bulk lifetime (tau(b)) of 12 mus can achieve a lifetime as high as 135 mus by process-induced gettering. Internal quantum efficiency (IQE) measurements reveal that the effective diffusion length (L(eff)) in the finished devices is 244 mum (or close to 90% of the total device width). Detailed cell analysis shows that for this combination of tau(b) and L(eff), the back surface recombination velocity (S(b)) of 10 000 cm/s or higher is the dominant efficiency limiting factor in the uniform regions of these mc-Si devices. Lowering S(b) can raise the efficiency of untextured HEM mc-Si solar cells above 19.0%, thus closing the efficiency gap between good quality, untextured single crystal and mc-Si solar cells