Solar cells based on carbon thin films

Carbon as an alternative material for low-cost and high-efficiency solar cell is attempted. Thin films of semiconducting n- (p-doped) and p- (un-doped) type carbon have been deposited on various substrates by ion beam sputtering and pyrolysis, using camphor as a natural carbon precursor. The optical gap of carbon has been found to be around 1.05 and <0.5 eV for n- and p- type films, respectively. Studies dealing with the temperature dependence of conductivity reveal semiconducting behavior of both the films and Hall measurements indicate n-type conduction of p-doped ion beam sputtered films and p-type conduction of un-doped pyrolysed films. Photovoltaic solar cells of configurations n-C/p-Si and n-C/p-C/p-Si have been fabricated and their photoresponse characteristics under AM 0 and 1 SUN illumination conditions have been studied. An enhanced efficiency of 1.52% has been obtained for the n-C/p-C/p-Si solar cell with the insertion of a p-C layer.