Energy level alignment in PCDTBT:PC70BM solar cells: Solution processed NiOx for improved hole collection and efficiency

► The energetic level alignment of PCDTBT and PC70BM was measured with UPS/IPES. ► The solid state electronic band gap of PCDTBT was found to be 2.2 eV. ► The solid state electronic band gap of 1:4 blend ratio of PCDTBT:PC70BM was found to be 1.5 eV. ► Energy level alignment differs on NiOx and PEDOT:PSS interlayers.