Photoelectrical properties of pulsed laser deposited boron doped p-carbon/n-silicon and phosphorus doped n-carbon/p-silicon heterojunction solar cells

This paper reports on the successful deposition of boron doped p-type (p-C:B) and phosphorus doped n-type (n-C:P) semiconducting carbon films and fabrication of p-C:B on n-type silicon (Si) substrate (p-C:B/n-Si) and n-C:P/p-Si cells by pulsed laser deposition at room temperature using graphite target. The B and P powder were respectively mixed with graphite powder in range from 1% to 20% of B by weight in the targets (Bwt.%) and 1–10% of P by weight in the targets (Pwt.%), and compressed into pellet targets. The B and P atoms incorporated in the films were determined by X-ray photoelectron spectroscopy to be in the range of 0.2–1.75 and 0.22–1.77 atomic percentages, respectively. The cells performances have been given under illumination I–V rectifying curve (AM 1.5, 100mW/cm2, 25 C). The open circuit voltage (Voc) and short circuit current density (Jsc) for p-C:B/n-Si are observed to vary from 230 to 250mV and 1.5 to 2.2mA/cm2, respectively. While, for n-C:P/p-Si cells the Voc and Jsc are observed to vary from 215 to 265mV and 7.5 to 10.5mA/cm2, respectively. The p-C:B/n-Si cells fabricated using 3 Bwt.% shows highest energy conversion efficiency, g = 0.20% and fill factor, FF = 45%. While, the n-C:P/p-Si cell fabricated using 7 Pwt.% shows highest of g = 1.14% and fill factor, FF = 41%. The quantum efficiency of p-C:B/n-Si and n-C:P/p-Si cells are observed to improve with percentage of B and P, respectively. The contribution of quantum efficiency in the lower wavelength region (below 750nm) may be due to the photon absorption by carbon layer and in the higher wavelength region is due to the Si substrates. 2004 Elsevier Ltd. All rights reserved.