Hydrogenated amorphous carbon films prepared by XeCl excimer pulsed laser deposition using compositional graphite and camphor target for solar cell applications

摘要

Hydrogenated amorphous carbon films (a-C:H) were deposited on p-type silicon (a C:H/p-Si) and quartz substrates by excimer laser at room temperature using mixture ratios 1 to 9 and 3 to 7 of camphor to graphite by weight percentages. The presence of hydrogen in the a-C:H films has been confirmed by Fourier transform infrared spectroscopy (FTIR) measurements. The structure and optical properties of a C:H films were respectively investigated by Raman scattering and UV-visible spectroscopy. The increase of sp(3) sites in the a-C:H films has also been confirmed by the Raman spectra spectroscopy analysis. The increase of the optical band gap with higher camphor percentage in the target was believed to be due to the increase of the sp3 hybrid forms of carbon arising from camphor incorporation. The formation of a heterojunction between the a-C:H film and Si substrate was confirmed by current-voltage (I-V) measurement. The structure of a-C:H/p-Si cells deposited using mixture ratios I to 9 of camphor to graphite by weight percentages showed better photovoltaic characteristics with an open-circuit voltage of 400 mV and short-circuit current density of about 15 mA/cm(2) under AM 1.5 (100 mW/cm(2) at room temperature) illumination. The energy conversion efficiency and fill factor were found to be approximately 2.1% and 0.38, respectively. The carbon layer contributed to the energy conversion efficiency in the lower wavelength region has been proved by the quantum efficiency measurement.