Transparent Conductive Oxides

ITO conductor tracks on glass
© Fraunhofer ISC
ITO conductor tracks on glass produced by pad printing

In optoelectronics, mainly indium tin oxide (ITO) and aluminium-doped zinc oxide (AZO) are used as transparent conductive materials. For large area depositions, wet chemical methods can hardly compete with e.g. sputtering techniques in terms of conductivity. However, when it comes to the direct production of lateral structures such as transparent conductive tracks, coating solutions from ITO or AZO can be printed directly. Pad printing and inkjet processes are suitable for this purpose.

Alternatively, transparent conductive layers can also be realized by composites of hybrid polymers with silver nanowires.

P-type Transparent Conductive Oxides

p-type delafossite layers
© Fraunhofer ISC
Specific resistance and transparency of doped p-type delafossite layers.

Delafossites such as CuAlO2 and CuCrO2 have attracted considerable scientific and technological attention due to their p-type conductivity and transparency. Even though the electrical performance of these materials will never be able to compete with the well-established n-type transparent conductors such as Al-doped zinc oxide (AZO) or indium-tin oxide (ITO) the combination of such n- and p- semiconductors may enable the fabrication of transparent electronics and optoelectronics. Devices such as transparent diodes transistors, UV-LEDs and applications in photovoltaic cells are envisioned.