Dilip Chandra Ghimire

Role of Amorphous Carbon Thin Film Cells Developed by Microwave Surface Wave Plasma CVD for Photovoltaic Energy Application

The a-C thin films were deposited by various techniques including a newly developed microwave (MW) surface-wave plasma (SWP) chemical vapor deposition (CVD) technique for solar cell application. The optical, structural, electrical and electronic properties of the films were studied by UV/VIS/NIR spectroscopy, AFM, Raman, X-ray photoelectron spectroscopy (XPS) and current-voltage (I-V) measurements. In this paper, we report experimental results of the optical, structural and photovoltaic properties of the a-C thin films; the results suggested that it is possible to control film growth rate and optical band gap with increasing gas composition pressure (GCP) inside the film deposition chamber consequently improve photoconductivity by proper selection of deposition parameters. Our research work is in progressing stage to realize cheap, high efficiency and environmentally friendly a-C based photovoltaic solar cell in near future

Enhanced photovoltaic properties of a-C/Si heterojunction solar cells

Boron doped amorphous carbon (a-C) thin films were synthesized by microwave surface wave plasma (MW SWP) chemical vapor deposition (CVD). The XPS results show successful doping of boron into the films, whereas atomic concentration of B into the films was about 1.6 at. %. Hall measurements indicate that the films were p-type in semiconducting nature. TEM and Raman results showed that the some graphene layers are grown into the a-C film. The photovoltaic measurement of a-C:B/n-Si heterojunction solar cell displayed rectifying I-V characteristics under dark and illumination (AM 1.5 100 mW/cm2) showed photovoltaic behavior with open-circuit voltage (Voc) of 0.21 V, short circuit current density (Jsc) of 31.88 mA/cm2, fill factor (FF) of 0.36 and conversion efficiency (η) of 2.4 %. The films show photoconductive.

Some aspects of nitrogen doped amorphous carbon thin films

Optical, structural and photovoltaic properties of amorphous carbon (a-C) thin films deposited on p-type silicon (p-Si) and quartz substrates by microwave (MW) surface-wave plasma (SWP) chemical vapor deposition (CVD) were analyzed in this paper. Argon (Ar: 200 sccm) was used as carrier gas while acetylene (C2H2: 20 sccm) and nitrogen (N: 0 and 10 sccm) were used as plasma source. Analytical methods such as X-ray photoelectron spectroscopy (XPS), Raman and UV-visible spectroscopy were employed to investigate the structural and optical properties of the a-C thin films respectively. The optical gaps of the films were tailored from 1.2 eV to 0.9 eV with nitrogen doping. Nitrogen doped a-C (a-C:N) thin film showed the photoconductivity action under white light illumination and hence Au/a-C:N/p-Si/Au heterojunction solar cell was fabricated with 0.23 V open circuit voltage, fill factor 25 and efficiency 5.7* 10−3 %.

Photovoltaic Properties of a-C:N/p-Si Heterojunction Solar Cell Synthesized by Microwave Surface Wave Plasma CVD

Amorphous carbon (a-C) thin films have been synthesized by microwave surface wave plasma chemical vapor deposition at low temperature (<100 degC). The influence of nitrogen doping on the properties a-C films is reported. Argon, acetylene and nitrogen (N) were used as a carrier, source and dopant gases. Analytical methods such as X-ray photoelectron spectroscopy (XPS), Nanopics 2100/NPX200 surface profiler, JASCO V-570 UV/VIS/NIR spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and Solar simulator were employed to investigate chemical, optical, structural and electrical properties of the films. Successfully nitrogen incorporated (29.37 at. %) into the film was found. The optical band gaps decreased from 2.7 to 1.7 eV. The photovoltaic measurements of a-C:N/p-Si structure show that the open-circuit voltage (Voc) of 4.7 mV and a short-circuit current density (Jsc) of 19.6 muA/cm2 under light illumination (AM 1.5 100 mW/cm2). The energy conversion efficiency and fill factor of the solar cell were found to be 2.24times10-4 % and 0.24 respectively

Compositional and structural variations of nitrogen doped amorphous carbon films grown by surface-wave mode microwave plasma CVD

In this paper, we report the effect of acetylene (C<inf>2</inf>H<inf>2</inf>) flow rates (5 to 20 sccm) on the compositional and structural variations of nitrogen doped amorphous carbon (a-C:N) thin films grown by surface-wave mode microwave plasma chemical vapor deposition at low temperature (≪100 °C). Argon was used as the main plasma source gas. The films were characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV/VIS/NIR spectroscopy and Fourier transform infrared spectroscopy (FTIR) measurements. The deposition rate of the films was typically 10 nm/min. The Tauc optical band gap of the films was in the range 1.6–1.8 eV. The XPS results show successful doping of nitrogen in the films, whereas N atomic concentration (at.%) into the films varied in the range of 23 to 35%. The N at.% in the films did not correlate with the increase of C<inf>2</inf>H<inf>2</inf> flow rate (i.e. decrease of nitrogen gas concentration). The maximum percentage of nitrogen take up was observed in the film grown at C<inf>2</inf>H<inf>2</inf> flow rate of 10 sccm. The FTIR results show enhanced contribution of C=C sp² and C-N sp³ bonds with increasing C<inf>2</inf>H<inf>2</inf> flow rate. The increase of C-H vibration mode around 3300 cm⁻¹ indicates the increase of sp³-bonded carbon in the films. The amorphous nature of the films was qualitatively understood from the Raman results.

Effect of process parameters on the properties of diamond like carbon films deposition by microwave surface-wave plasma CVD

Diamond like carbon (DLC) thin films were deposited on various substrates, such as, silicon, quartz and ITO substrates at low temperature (≪100 °C) by microwave (MW) surface-wave plasma (SWP) chemical vapor deposition (CVD), for solar cell application. The methane (CH4), ethylene (C2H4) and acetylene (C2H2) were used as carbon precursors, while argon was used as carrier gas. Nitrogen is used as dopant. The deposited DLC films were characterized by UV/VIS/NIR spectrophotometer, Raman, FT-IR and XPS measurements. In this paper, we report some experimental results of the optical and structural properties of the films; the results suggested that it is possible to control film growth rate and optical band gap, and consequently improve photoconductivity by proper selection of deposition parameters, optimizing dopants and appropriate deposition temperature. Our research work can be realize cheap, reasonably environmentally friendly and high efficiency solar cell.

Energy Demand, Availability in Nepal and Present PV Cost Analysis

This paper describes the Photovoltaic solar electricity generating capacity in Nepal. Although Nepal is rich in hydropower, currently only about 17% of the total population has access of electricity. The majority of the population who are living in the rural mountainous parts of Nepal is still deprived of electricity. The relatively high insulation throughout the year and geographical situation encourage for the development of PV energy in the country. The monthly mean solar radiation analysis shows that April and January receive the highest and the lowest solar radiation respectively. The PV installation rate has increased dramatically in the last five years due to relative decrease in PV module cost and government subsidy. PV technology is reliable because of its simplicity, extremely low maintenance cost and point-of-use installation possibility. The widespread use of PV will help to reduce CO2 emission and consequently contributes towards better environment.Copyright