Characterization of ALD Processed Gallium Doped TiO2 Hole Blocking Layer in an Inverted Organic Solar Cell

To improve power conversion efficiency (PCE) of inverted structure organic solar cells a buffer layer, a hole blocking layer (HBL) was introduced between cathode and active photovoltaic layer. Gallium (Ga) doped TiO2 as a HBL was fabricated by means of atomic layer deposition. X-ray photoelectron spectroscopy showed the highest Ga-Ti complex binding characteristics was achieved at 5% doping concentration. Gallium doped TiO2 layer exhibited over 94% of optical transmittance at the process temperature of 200A degrees C. The resulting PCE of inverted structure organic solar cell having 5% doping in the hole block layer was 2.7%. The PCE was improved 35% compared to the cell without gallium doping.