HW-CVD deposited μc-Si:H for the inverted heterojunction solar cell

Abstract

P-type-microcrystalline-silicon / n-type-crystalline-silicon hetero-junction solar cell has been prepared by means of hot-wire chemical vapor deposition (HW-CVD) technique. The solar cell structure was illuminated on the opposite side of the normally-formed heterojunction. With this inverted structure, the photovoltaic cell has the design potential to improve the light-incident surface-texturing with the possibility to avoid the use of transparent conducting oxide (TCO). Solar cells were fabricated on Czochralsky (CZ)-grown phosphorous-doped crystalline-silicon (c-Si) substrates within 0.5 to 1 ohm-cm. HW-CVD has employed for the deposition of a very thin intrinsic hydrogenated amorphous silicon (i-a-Si) as a buffer-layer as a heterojunction interface, and boron-doped hydrogenated microcrystalline silicon (p-μc-Si) on c-Si substrate. The tungsten catalyst temperature (Tfil) was settled to 1600 °C and 1950 °C for i-a-Si and p-μc-Si films, respectively. Silane (SiH4), hydrogen (H2) and diluted diborane (B2H6) gases were used for p-μc-Si at the substrate temperatures (Tsub) of 200 °C. The obtained I–V characteristics under simulated solar radiation at 100mW/cm2 are: Jsc =26.1 mA/cm2; Voc = 545 mV; Jm = 21.4 mA/cm2; Vm = 410 mV; FF = 61.7%, with total area efficiency of η= 8.8%. The solar cell has great potential to improve its conversion efficiency with proper surface passivation and antireflection coat.