Thin Solid Films, Vol.570, 129-133, 2014
Deposition of low sheet resistance indium tin oxide directly onto functional small molecules
We outline a methodology for depositing tin-doped indium oxide (ITO) directly onto semiconducting organic smallmolecule films for use as a transparent conducting oxide top-electrode. ITO filmswere grown using pulsed laser deposition onto copper(II) phthalocyanine (CuPc): buckminsterfullerene (C-60) coated substrates. The ITO was deposited at a substrate temperature of 150 degrees C over a wide range of background oxygen pressures (P-d) (0.67-10 Pa). Deposition at 0.67 <= P-d <= 4.7 Pa led to delamination of the organic films owing to damage induced by the high energy ablated particles, at intermediate 4.7 <= P-d <= 6.7 Pa pressures macroscopic cracking is observed in the ITO. Increasing P-d further, >= 6.7 Pa, supports the deposition of continuous, polycrystalline and highly transparent ITO filmswithout damage to the CuPc: C-60. The free carrier concentration of ITO is strongly influenced by P-d; hence growth at >6.7 Pa induces a significant decrease in conductivity; with a minimum sheet resistance (R-s) of 145 Omega/square achieved for 300 nm thick ITO films. To reduce the R-s a multi-pressure deposition was implemented, resulting in the formation of polycrystalline, highly transparent ITO with an R-s of similar to 20 Omega/square whilst maintaining the inherent functionality and integrity of the small molecule substrate. (C) 2014 Published by Elsevier B.V.
Keywords:Transparent conducting oxides;Indium tin oxide;Pulsed laser deposition;Small molecules;Photovoltaics