ITO substrates of sheet resistance 8-12 ohm and 20 ohm are there. which one is better for the fabrication of both oraganic and perovskite solarcells.
Dear Pratheek,
ITO as a transparent electrode is required not only to have a low sheet resistance and also the smooth surface. The low sheet resistance can reduce the heat generating from the current path through. The smooth surface can minimum the spikes or shorts within the cells. When you select a batch of ITO substrates, the above two criteria have to be considered. Sometimes the chemical formulation of ITO may also need to consider due to the slight difference of work function, which determines the charge carrier injection from electrodes.
Best wishes
Xuhua
Article Effect of Sheet Resistance and Morphology of ITO Thin Films ...
Dear Tioual,
28 ohm/Sq is quite large sheet resistance for ITO. It is definitely not good to make efficient devices. Once ITO subatrates are made, the sheet resistances are determined. Coating an extra layer to reduce the sheet resistance could cause other problems such as loosing transparency.
Hope it is clear.
Best
Xuhua
The thin layer of ITO has a sheet resistance Rs= roh/ d, where roh is the resistivity and d is the thickness. This sheet resistance must be as small as possible. Ideally it must be zero. However, this condition can not be practically realized. More realistic requirement is to make the resistance of this layer much smaller than the resistances of the other layers of the solar cells especially the hole transport layer and the electron transport layer. The resistivity roh of ITO = 10^-4 ohm.cm, with thickness of about one micrometer then the resistance of this layer = roh L/AREA,
Assuming 1 cm^2 area , then R of the layer= 10^-4 x 10-4/1= 10^-8 ohm. So, the bulk resistance of the layer is very small. But what is more important is the contact resistance of the this layer with the electron transport layer or the hole transport layer since ITO must build low ohmic contact with either one one such layers. One has to take care of such contact resistance.
One has to notice that the sheet resistance Rs= 10^-4/ 10^-4= one ohm per square.
Best wishes
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