Highly effective electronic passivation of silicon surfaces by atomic layer deposited hafnium oxide

This paper investigates the application of hafnium oxide (HfO2) thin films to crystalline silicon (c-Si) solar cells. Excellent passivation of both n-and p-type crystalline silicon surfaces has been achieved by the application of thin HfO2 films prepared by atomic layer deposition. Effective surface recombination velocities as low as 3.3 and 9.9 cm s(-1) have been recorded with 15nm thick films on n- and p-type 1 Omega cm c-Si, respectively. The surface passivation by HfO2 is activated at 350 degrees C by a forming gas anneal. Capacitance voltage measurement shows an interface state density of 3.6 x 10(10) cm(-2) eV(-1) and a positive charge density of 5 x 10(11) cm(-2) on annealed p-type 1 Omega cm c-Si. X-ray diffraction unveils a positive correlation between surface recombination and crystallinity of the HfO2 and a dependence of the crystallinity on both annealing temperature and film thickness. In summary, HfO2 is demonstrated to be an excellent candidate for surface passivation of crystalline silicon solar cells. Published by AIP Publishing.