A solar cell apparatus 100 and a method for forming said solar cell apparatus 100, comprising a substrate 101, a n-type transparent conductive oxide (TCO) layer 102 deposited atop said substrate 101, a p-i-n structure 200 that includes a p-type layer 103, an i-type layer 104, a n-type layer 105, a metal back layer 106 deposited atop said n-type layer 105 of the p-i-n structure 200. The n-type layer 105 comprises n-type donors 115 including phosphorus atoms. The n-type donors 115 include oxygen atoms at an atomic concentration comprised between 5% and 25% of the overall atomic composition of the n-type layer 105.