No abstract

Excellent passivation properties of hydrogenated amorphous silicon oxide (a-SiOx:H) prepared by very high frequency plasma-enhanced chemical vapor deposition (VHF PECVD) at a low substrate temperature (170 °C) on crystalline and polycrystalline silicon (Si) wafers are reported. Films were characterized by ellipsometry, Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible (UV–vis) spectrophotometry, and dark-conductivity and photoconductivity measurements. A comparison of the results with those for different passivation layers such as hydrogenated amorphous silicon carbon nitride (a-SiCxNy:H), hydrogenated amorphous silicon nitride (a-SiNx:H), and hydrogenated amorphous silicon (a-Si:H) reveals their superiority as an excellent passivation layer for p-type crystalline Si as well as polycrystalline Si. A maximum effective lifetime of 400 µs was measured for 1–10 Ω cm, 380-µm-thick p-type c-Si using a micro-photocurrent decay (µ-PCD) system. Fixed charge density (Qf) was estimated by high-frequency (1 MHz) capacitance–voltage measurement using a metal–insulator–silicon structure (CV-MIS). The effect of annealing temperature on surface passivation in a nitrogen atmosphere was also studied.

We have developed n-type microcrystalline hydrogenated silicon oxide (n-µc-SiO : H) thin films by the radio frequency plasma enhanced chemical vapour deposition (RF-PECVD, 13.56 MHz) method having suitable characteristics for use in the fabrication of single or multijunction amorphous silicon (a-Si) solar cells. The films have been characterized in detail for the study of structural and optoelectronic properties. Transmission electron microscopy, Raman spectroscopy, x-ray diffraction, Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy have been used for the structural studies. The dependence of the structure and optoelectronic properties of n-µc-SiO : H films on the various deposition parameters such as hydrogen dilution, chamber pressure, RF-power density etc have also been studied. Comparison of the properties between n-µc-SiO : H and n-µc-Si : H films have been studied, too, which shows that the former has higher optical gap (2.17 eV) and lower activation energy (0.015 eV) with similar electrical conductivity (12.08 S cm-1).

The n-type microcrystalline cubic silicon carbide (mc-3C-SiC:H) films were deposited by hot wire chemical vapor deposition (HWCVD) at a low substrate temperature ($300 C). Heterojunction silicon based photovoltaic devices were fabricated by depositing wide band gap n-type mc-3C-SiC thin films on p-type Si wafers, whose thickness and resistivity were 200 mm and 1-10 cm, respectively. The silicon wafers were textured using alkaline etchant prior to the device fabrication. The photovoltaic parameters of a typical device were found to be V oc ¼ 560 mV, J sc ¼ 35:0 mA/cm 2 , fill factor (F.F.) = 0.724, and ¼ 14:20%. Numerical analysis was performed using automat for simulation of hetero structures (AFORS-HET), a onedimensional device simulators to determine the probable cause of the changes in device parameters before and after the ageing of the filament.

Wide gap, highly conducting n-type hydrogenated microcrystalline silicon oxide (μc-SiO : H) films were prepared by very high frequency plasma enhanced chemical vapour deposition at a very low substrate temperature (170 °C) as an alternative to amorphous silicon (a-Si : H) for use as an emitter layer of heterojunction solar cells. The optoelectronic properties of n-μc-SiO : H films prepared for the emitter layer are dark conductivity = 0.51 S cm−1 at 20 nm thin film, activation energy = 23 meV and E04 = 2.3 eV. Czochralski-grown 380 µm thick p-type ⟨1 0 0⟩ oriented polished silicon wafers with a resistivity of 1–10 Ω cm were used for the fabrication of heterojunction solar cells. Photovoltaic parameters of the device were found to be Voc = 620 mV, Jsc = 32.1 mA cm−2, FF = 0.77, η = 15.32% (active area efficiency).