Recombination center in C 60/p-Si heterojunction and solar cells

Abstract

Deep level transient spectroscopy (DLTS) has been used to detect the contribution of interface-related states, responsible for minority carrier lifetime reduction in C 60/p-Si solar cells. The very low efficiency of C 60 based solar cells is found to be due to the presence of one hole level E V +0.70 eV at the interface of C 60/p-Si heterojunction. The hole capture cross-section and the variation with temperature have been determined, to account for minority carrier lifetime of the material. A large barrier for hole capture, implying a large electron–phonon interaction, characterizes the observed hole level. A pronounced reduction in DLTS peak of the dominant level ( 0.70 eV ) due to injection of electrons provides evidence of electron–hole recombination. A detailed characterization indicates that a dominant deep level, with comparable electron and hole emission rates, acts as a recombination center, which governs the minority-carrier lifetime