Table 1 Worldwide PV Module Production in 2003 by Technology TypeTechnology Type
MW
%Flat plates – single-crystal silicon 230.5 31.0
Cast poly/multicrystalline silicon 443.8 59.6
Ribbon silicon 22.8 3.1
Thin-film amorphous silicon 39.3 5.3
Thin-film cadmium telluride 3 0.4
Thin-film CIGS 4 0.5
Concentrators – silicon 0.7 0.1
TOTALS 744.1 100
Source: PV NewsFlat-plate Systems
Flat-plate Crystalline Silicon. Of the PV modules produced today, nearly 94% are based on
crystalline silicon wafer technologies. Of this total, about 30% are based on conventional, single-
crystal silicon grown by the Czochralski ingot process, 60% are based on polycrystalline (also
referred to as multicrystalline) ingots cast in a crucible, and 3% are from silicon ribbons/sheet
produced by various processes.
Ingot-based Technologies. The silicon solar cells with the highest efficiency to date (24.7% in
Figure 66) have been made with single-crystal, float-zone silicon, but the commercial use of
float-zone silicon for PV has started only recently. Using back-contact solar cell design, 21.5%
efficiency has been achieved with long lifetime (>1 ms), n-type float-zone silicon wafers
(Mulligan et al. 2004).
Single-crystal silicon grown by the Czochralski technique still constitutes a sizable portion of the
PV market (Table 1). Several cell designs have achieved efficiencies of >21% (Tanaka et al.
2003) and >18% (Bruton et al. 2003). Efforts to improve Czochralski growth for PV typically
focus on reducing consumable materials and energy costs — melt replenishment, crucible
development (lower cost and longer lifetime), furnace hot-zone designs, growth ambient control,
increase in ingot diameter and length, and extensive studies of the effects of defects and
impurities.
By far the fastest growing segment of the PV industry (Table 1) is that based on casting large,
multicrystalline ingots in some crucible that is usually consumed in the process. The grain sizes
are typically in the millimeter to centimeter range in width and columnar (several centimeters in
length) along the solidification direction. Manufacturers routinely fabricate large multicrystalline
silicon solar cells with efficiencies in the 13–15% range; small-area research cells are 20%
efficient.