PHOTOELECTRICAL PROPERTIES OFp-TYPE ANDn-TYPE ELECTRICAL CONDUCTIVITY AMORPHOUS CARBON THIN FILMS FOR APPLICATION IN ECONOMICAL CARBON-BASED SOLAR CELLS

The successful deposition of boron(B)-doped p-type(p-C:B)and phosphorous(P)-doped n-type(n-C:P)carbon(C)films, and fabrication ofp-C:Bon silicon(Si)substrate(p-C:B/n-Si)andn-C:P/p-Sicells by the technique of pulsed laser deposition (PLD) using graphite target is reported. The cells' performances are represented in the dark I–V rectifying curve and I–V working curve under illumination when exposed to AM 1.5 illumination condition (100 mW/cm2, 25°C). The open circuit voltage(Voc)and short circuit current density(Jsc)forp-C:B/n-Siare observed to vary from 230–250 mV and 1.5–2.2 mA/cm2, respectively, and to vary from 215–265 mV and 7.5–10.5 mA/cm2, respectively, forn-C:P/p-Sicells. Thep-C:B/n-Sicell fabricated using the target with the amount ofBby 3 Bwt% shows highest energy conversion efficiency, η = 0.20%, and fill factor, FF = 45%, while, then-C:P/p-Sicell with the amount ofPby 7 Pwt% shows highest energy conversion efficiency, η = 1.14%, and fill factor, FF = 41%. The quantum efficiencies (QE) of thep-C:B/n-Siandn-C:P/p-Sicells are observed to improve with Bwt% and Pwt%, respectively. The contributions of QE are suggested to be due to photon absorption by carbon layer in the lower wavelength region (below 750 nm) andSisubstrates in the higher wavelength region. The dependence ofBandPcontent on the electrical and optical properties of the deposited films, and the photovoltaic characteristics of the respectivep-C:B/n-Siandn-C:P/p-Siheterojunction photovoltaic cells, are discussed.