Recent progress in MIS solar cells

Metal–insulator–semiconductor (MIS)‐type solar cells have an inherent cost advantage compared to p‐n junction solar cells. First‐generation MIS–inversion layer (MIS–IL) solar cells, already successfully produced in an industrial pilot line, are restricted to efficiencies of 15–16%. With the second‐generation MIS–IL silicon solar cells, based on drastically improved surface passivation by plasma‐enhanced chemical vapour‐deposited silicon nitride, simple technology can be combined with very high efficiencies. The novel inversion layer emitters have the potential to outperform conventional phosphorus‐diffused emitters of Si solar cells. A 17.1% efficiency could already be achieved with the novel point‐contacted ‘truncated pyramid’ MIS–IL cell. A new surface‐grooved line‐contact MIS–IL device presently under development using unconventional processing steps applicable for large‐scale fabrication is discussed. By the mechanical grooving technique, contact widths down to 2 μm can be achieved homogeneously over large wafer areas. Bifacial sensitivity is included in most of the MIS‐type solar cells. For a bifacial 98 cm 2 Czochralski (Cz) Si MIS‐contacted p‐n junction solar cell with a random pyramid surface texture and Al as grid metal, efficiencies of 16.5% for front and 13.8% for rear side illumination are reported. A 19.5% efficiency has been obtained with a mechanically grooved MIS n + p solar cell. The MIS‐type silicon solar cells are able to significantly lower the costs for solar electricity due to the simple technology and the potential for efficiencies well above 20%.©1997 John Wiley & Sons, Ltd.