Dear researchers,
I am currently trying to perform I-V measurements for thin films. Could anybody let me know what is the best way to perform I-V measurements using Keithley 2600. How to make good top contacts for good I-V data. Any kind of suggestion or some discussion would be helpful.
Hi Aditya,
I think you must try to put the silver ink over the top electrode and ITO contact before measuring. For J-V measurement, it is useful to prepare the device holder with containing the contact pins, or you may directly connect with crocodile pins.
Also, the buffer layer (ZnO/PEDOT: PSS) coating completion on ITO, try to remove (before film annealing) the film from edges to make good contact with ITO and silver ink (or directly crocodile pin).
I hope it will help.
The simplest way is to use some liquid electrode as the top contact. Of course, in reality it becomes the bottom electrode, as otherwise liquid runs away, but this naming confusion is a minor thing... Not only Hg is liquid at room temperature, also an InGa alloy can be used. There are some draw back in this simplicity. The metal surface is always oxidized, and small crystals in the liquid metal can damage the film, therefore results are not well reproducible.
You can evaporate Au, Ag, or Cu (or whatever you want) right on top of organics, using a mask. The mask can be made as a metal or plastic sheet with holes e.g. 1...2 mm in diameter, placed at 0.1 to 0.5 mm from the surface. The hardest trick is to do evaporation slowly enough. Often this means that you cannot measure the speed of evaporation, since it is below sensitivity. Then you make a connection to this evaporated electrode with a liquid metal contact.
The above two methods do not need any operations with the bottom electrode. If you can etch the transparent electrode, then you better do the following. Form (by etching) one common bottom transparent electrode and a set of small contact places for the top metal electrode. Make your films. Wash away the films from the small contact places before you make the metal electrodes. Using another mask, evaporate the top electrodes, each as a band, partly over the bottom electrode and partly over one of the small contact places. Only the part of the films between the two electrodes will work as a cell. In this case, you can use anything to make your connections, including simple alligator clips. An example of this design you can find e.g. in Article Role of a phthalocyanine-fullerene dyad in multilayered orga...
There are many ways to make a top contact.....
If you want to make good top contact, my suggestion is to make a photo-mask, and apply on the top of the thin film, after that use sputtering techniques (for polymeric sample best to use E-beam evaporation techniques) to deposit Chromium of first layer of thickness approximately 10 - 20 nm, over it a gold coating of thickness 90 – 80 nm.
Hi Aditya ,
I am not much understand your question because you are not mention here which type your thin film and which type metal to try deposited on thin film .
so if , you work on 3th generation solar cell like perovskite , organic and quantum dot solar cell than you may be use of Al , Au & Ag.
so regarding this type metal deposition you need to highly pure metal and proper mask to deposition metals.
also you take extra care when you deposited metal(Al, Au & Ag) by thermal deposition like vacuum pressure( >10^-6mbar) and thickness(80nm to 120nm) and deposition rate .
Well, I was trying to make top contacts by the help of silver ink, but i was unable to get good I-V data, so is there any other way to improve the top contact by methods other than masking or evaporation based.
Thank you Ram Datt Vladimir I Chukharev Braj Krishna Gaurav Gupta for responding to the query in an effective manner.
If you don't want to evaporate you can try different inks/adhesives. There's silver and carbon based inks and adhesives, and also InGa eutectic. But it depends what you're trying to contact - contacting metals is easy, contacting low-doped semiconductors is hard.
You can find the details electrical conductivity measurement for thin films using by a four-probe method in an attached paper. Expert researchers already suggested possible surface treatment before measuring the I-V plot.
There is yet another simple method to make a top electrode, with a soft conductive rubber. I know that it was successfully used for transient photovoltage measurements with stable and relatively thick films (micrometers) of bacteriorhodopsin.
Conductive rubber is usually made by adding a lot of soot (or other conductive dust) into rubber precursors before polymerization.
This contact has rather high resistivity and suits voltage measurements, while current measurements are difficult. And the film is mostly destroyed when the contact is removed. Otherwise, it's probably the simplest method.
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanostructures
- Thin Films