“Transport limiting mechanisms of amorphous (a-Si:H) and microcrystalline(mc-Si:H) thin film heterostructures for photovoltaic application”

Abstract

AbstractDirect conversion of sunlight into electricity employing amorphous (a-Si:H) and microcrystalline (mc-Si) silicon solar cell structures provides cheap, continuous, large-area device capability. However, the inherent instability due to light induced degradation of such cells poses a challenge for practical photovoltaic applications. To work around this problem, we have made use of a-Si:H/c-Si (crystalline) and mc-Si/c-Si heterostructures. Plasma decomposition of 2% silane gas (SiH4/He) in an ECR (electron cyclotron resonance)-CVD configuration forms the basis of the deposition technique. Electro-optical properties exhibit photoconductivity (σp) of 6.5×10−6 S/cm and a low dark conductivity (σd) of 1.4×10−9 S/cm for a-Si:H films and a relatively high σp of 2.1×10−4 S/cm and a high σd of 1.2×10−7 S/cm for mc-Si films. A possible multi-tunneling transport mechanism is evident for a low forward bias with the current conduction becoming space charge limited with increasing bias. The domination of this latter mechanism may be responsible for non-ideal junction behavior.