When we make a solar cell or diode, we etch part of the ITO to make the top contact separate from the ITO. (see the attachment) But in the device there still have a samll overlap of top contact and ITO, it is called active area. I am confused about it. Why we need to etch ITO? If it is inactive area, why we still make it. In lots of publications, they just say it is to avoid short circuit. But why you still have the overlap area (active area)? Thanks.
Hello
If you don't etch the part of ITO, the device area would be Ag electrode size. When you connect both electrodes, it is likely the Ag partial electrode generating spikes which is called "short circuit". That means the current through the Ag to ITO via the shortest distance. Even there are some semiconductors there, it causes the burning effect from the part which ITO should be etched away.
You could try to do it with two devices. You may understand it more.
Xuhua Wang But why we still keep part of ITO below Ag (the active area)? This active area still has possibility to generate short circuit.
@Yuqiang Gao the active area is the device forming from semiconductors sandwiched with positive electrode and negative electrode. Due to the charge transport nature of semiconductors, the electrode contacts are key to make devices work properly. Even the size and shape of electrode designs affect the device lifetime because of conductivity of electrodes.
Dear Mr. Gao,
In the left side of the figure, one will never get short-circuit between the ITO bottom layer and top Ag metal layer because of the presence of the hole transport layer material PEDT:PSS. Even it required that the active area be as large as possible. And therefore the figure above is not to scale.
The overlap area is the PV generator.
Best wishes
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