Advanced Technologies for Smart Windows.

CVD Graphene for direct transferred transparent contacts

Illustration CVD equipment
monolayer graphene growth on 150x150mm Cu foil

1 The idea behind

The objective is to replace indium tin oxide (ITO), which is the common material used as transparent conductive layer in electrical device, by graphene synthesised via chemical vapor deposition (CVD) and the use of a roll to plate process for the transfer. Graphene has a higher transparency than ITO and is a promising candidate for cost reduction, and for overcoming the shortage of indium supplying. Especially the roll to plate process that will be developed within the project is an easy and fast process to transfer CVD graphene from copper foils onto glass and will make it possible to handle graphene layers for mass production. The specific goal within MEM4WIN will be to fabricate large area CVD graphene, transfer it to glass and use it for OPVs, Micro Mirrors and OLEDs.

2 Advantages

Graphene layers should be capable of meeting the required minimum conductivities of 10-5 (for charge extraction layers) and area conductivities of 0.05 (for electrodes) while still providing transparencies of more than 80% over the whole visible and near infrared region.

3 Results

Within the framework of the MEM4WIN project we successfully achieved the transfer on glass plate of CVD graphene grown on copper. The investigation and optimisation works have led to a reliable CVD process for the preparation of defect free graphene. The developed transfer process has enabled the preparation of graphene on glass at lab scale. Four layers of graphene were grown and doped by CNR on glass and showed a resistivity around 25 Ω/□ and a transmittivity above 90%.

To enable large scale applications for graphene, all tools used for material growth and transfer needs to be scaled up. Within the project, a new CVD tool was developed. This new tool allows a significant throughput increase for the production of high quality monolayer graphene. This new equipment is capable of producing 400cm2/h of monolayer graphene. The concept for this new system is fully scalable and could be used to produce very large area graphene > 1x1m.

First integration in OPV cell of graphene transferred on glass was realized. This attempt showed that with CVD Graphene it is possible to make functional solar cells and that the optical density is good. The OPV cell tested consisted of a layer stack of ZnO, P3HT:PCBM, and HIL were coated and a 300 nm Ag electrode was evaporated. The first trial gave 40%FF and 0.8% efficiency, which is very promising. With the optimized transfer process and with graphene doping, a stable sheet resistance of 35Ω/□ at a transparency of 90,2% were obtained with a 4-layer-graphene sample (5x5cm).

4 Contact

For Doped CVD Graphene for direct transferred transparent contacts, please contact:
Giovanni Bruno
+39.080.5442082 / under construction

For CVD Graphene growth equipment, please contact
Prof. Dr. Michael Heuken
+49 (2407) 9030-335