2. Experiments and measurements
The a-SiGe thin films are fabricated in a capacitively coupled
radio frequency plasma enhanced chemical vapor deposition (RFPECVD)
system with a base vacuum of 105 Pa. The substrate
temperature is fixed at 270 C. The reactive gases for the deposition
of thin films include silane (SiH4), germane (GeH4), hydrogen (H2),
trimethylboron (TMB) and phosphine (PH3). The flow rate is shown
in standard cubic centimeters per minute (sccm). The pressure and
gas flow are independently controlled by a downstream throttle
valve controller and upstream mass flow controllers, respectively.
The solar cells are fabricated with the structure of glass/textured
SnO2:F/p-i-n a-SiGe/ITO/Ag. The area is 0.30 cm2
. The ITO films are
deposited by intermediate frequency magnetron sputtering from a
sintered ceramic SnO2-doped In2O3 (10 wt.%) in an argon atmosphere.
The Ag films are obtained by direct current magnetron
sputtering from pure Ag target, respectively.