Using hydrogen‐doped In2O3 films as a transparent back contact in (Ag, Cu)(In, Ga)Se2 solar cells. (11th January 2018) - Keller, Jan
Abstract: This study evaluates the potential of hydrogen‐doped In2 O3 (IOH) as a transparent back contact material in (Agy, Cu1‐y )(In1‐x, Gax )Se2 solar cells. It is found that the presence of Na promotes the creation of Ga2 O3 at the back contact during (Agy, Cu1‐y )(In1‐x, Gax )Se2 growth. An excessive Ga2 O3 formation results in a Ga depletion, which extends deep into the absorber layer. Consequently, the beneficial back surface field is removed and a detrimental reversed electrical field establishes. However, for more moderate Ga2 O3 amounts (obtained with reduced Na supply), the back surface field can be preserved. Characterization of corresponding solar cells suggests the presence of an ohmic back contact, even at absorber deposition temperatures of 550°C. The best solar cell with an IOH back contact shows a fill factor of 74% and an efficiency ( η ) of 16.1% (without antireflection coating). The results indicate that Ga2 O3 does not necessarily act as a transport barrier in the investigated system. Observed losses in open circuit voltage ( V OC ) as compared to reference samples with a Mo back contact are ascribed to a lower Na concentration in the absorber layer. Abstract : This contribution illustrated the great potential of hydrogenated In2 O3 (IOH) films as a transparent back contact material in chalcopyrite solar cells. A well‐adjusted sodium incorporation results in an ohmic back contact and a sufficient lateral conductivity, even after absorber deposition temperatures as high as 550°C. A solar cell with a fill factor of 74% and an efficiency of 16.1% could be fabricated on an IOH back contact and without the aid of any additional supporting layers.