A lot of works are devoted now to integrate driving TFT with OLED, minimizing the area of the pixel. In other part, people try to fabricate devices using low cost technologies as deposition in solution avoiding any photolithography step in the process. Finally, it can be better if the full driving TFT-OLED device is transparent.

The present work try to answer simultaneously to these 3 desires. Particularly, the present paper focus on the TFT.

Vertical TFT will answer to the first desire to minimize the area of the device. It is based here on a stack of the gate, the insulator, the source, the semiconducting active layer and the drain; meaning 5 films all solution deposited.

Thanks to the present available insulator solutions for the deposition, different insulators can be chosen. High k HFO₂ insulator is chosen in this work. It is is spincoated and then annealed at 300C during 1 hour. Figure 1 shows the current-voltage curves of ITO/HFO₂/AgNWs stack. After rapid increase, the current stabilizes at 10 pAmp at least still a voltage of 10V, meaning a field of 7.7x10⁵ V/cm² with a thickness of 130 nm. Present HFO₂ film is then a good insulator.

ZnO is chosen as active layer. It is spin-coated and then annealed at 180C. This temperature was found enough high to lower the conductivity (Figure 2)

The source and drain layers are spin-coated using Ag nanowires (AgNWs) solution. As source AgNWs layer is deposited before ZnO layer, it will be annealed at the same temperature 180C. Figure 3 shows that AgNWs film stays enough conducting after such annealing temperature. It can be used as conducting source and drain.

Finally, the full stack of 5 films is characterized as a TFT.

Figure 4 shows the transfer characteristic of this TFT plotted at a drain voltage of 2.6V. The drain current is modulated by 4 orders from off to on regime.

Very simple and low cost fully in solution process is presented in this work. Working transparent TFT is demonstrated. The process shows its high potential in the development of integrated TFT-OLED in small area. It is very promising.

Its shows also the need of future hard work in this way to demonstrate fully integrated driving TFT-OLED