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Chapter 18 • Thin Film Photovoltaics 367
solar Frontier (Japan) leads the production on Cis technology with annual production
capacity over 1 GW and has plans to enter BiPV market with the use of aluminium in place
of glass to reduce the weight of the modules.
18.2.4 Perovskite
Perovskite solar cells stem from dye-sensitized solar cells but have promising solid state
structures as well as rapid efficiency leaps (Fig. 18.4), which have now reached 22.7% [2].
Most commonly, CH 3 NH 3 PbI 3 based organic–inorganic perovskite materials have been
used in these types of solar cells due to their high charge carrier mobility. High mobility
is important because, together with high charge carrier lifetimes, it means that the light-
generated electrons and holes can move large enough distances to be extracted as current,
instead of losing their energy as heat within the cell [19]. Moreover, the perovskite solar
cells can be deposited by low-temperature methods such as solution process viz. spin
coating, spray deposition, and thermal evaporation methods.
18.3 Deposition and Growth Techniques
Room temperature deposition allows the use of a variety of substrates such as glass, metal,
and plastics but often results in inferior module efficiencies and quality. Two most com-
monly used methods for a-si are plasma enhanced chemical vapor deposition (PeCVd)
and glow discharge CVd. For high deposition rates the deposition technologies based on
very high frequency (VhF), microwave and high-pressure plasma are currently being pur-
sued. Alternative deposition methods using hot wire CVd (hWCVd) technique, electron
cyclotron resonance reactor (eCR) and also the combination of hWCVd and PeCVd are
also being carried out to increase the deposition rate [1,10,20–22]. Vacuum Evaporation is
a simple deposition method allowing low temperatures for CdTe and CiGs cells. Vacuum
evaporation method involves simultaneous evaporation of the constituent elements from
multiple sources in single or sequential processes during the whole absorber deposition
process [23]. There is a substantial interest in testing different deposition techniques for
CiGs which could improve the technology greatly. some methods include: nanosized pre-
cursor particles and electro-deposition from a chemical bath. A hybrid approach that uses
additional vacuum deposition on electrodeposited precursor layers has also been inves-
tigated [24]. Closed Space Sublimation (CSS) and vapor transport (VT) are the prominent
−1
and industrially used processes for CdTe deposition owing to its very high rate (2–5 µ min )
of deposition. First solar is the most successful CdTe company to date with an annual pro-
2
duction capacity of approximately 3 GWp for modules on 60 × 120 cm glass substrates.
Ge global research has achieved a ground-breaking efficiency of 19.6% on glass substrates.
early 2014 First solar communicated 20.4% solar cell efficiency and a very remarkable
full scale module efficiency of 17%. details of other alternative methods such as screen-
printing, spray pyrolysis, moCVd, CVd and atomic layer deposition (ALd) and electro-
deposition (ed) are also possible [11,13,23,24]. For flexible substrates such as polymers low
temperature methods like sputtering, hVe, and electro-deposition (ed) are suitable.