Current Voltage Luminance Testing System for OLEDs

[Plexonite]

This is going to be a message board for a OLED/LED Current-Voltage-Luminance (IVL) testing system that I am in process of developing.  The system will be capable of electrically categorizing 36 pixels(9 Devices, 4 pixels each) by performing a reverse bias to forward bias voltage sweep.  The system will also measure the light output of a pixel by monitoring the current(A) output of a photodiode.  To calibrate the light output the pixels are measured at fixed current density specified by the user before the IVL test using a Luminance meter.  The system consist of two keithley 2400 source meters and a keithley 7001 Switch System.  One keithley is use to source voltage(V) measure current(A) and the other is used to monitor photodiode current.  The switch is used to switch between the 36 pixels.  

Eventually I will post the entire project but for now I would like to get some comments on performing a single IVL sweep on a single pixel.  I was unable to get the triggering feature to work with keithley's in labview so I had to use sequence structures.  I just took the Labview Core 3 and DAQ classes,  if possible I would like to implement some of the parallel processing which I learned.  I will attach the file VI's in the next post.

[Plexonite]

Here are the important vis

[Plexonite]

Let me know if you need to view any others. Again any comments would be appreciated

[weberkp]

I have developed a simple OLED V-I-L system that employs an NI GPIB connection to a Keithley 2400 SourceMeter and a USB controlled TOPCON BM-7A Colorimeter interfaced with a VBA macro-enabled Microsoft Excel 2003 workbook as the front-end. I made good use of the sample program "ni-488.2_in_excel.xls" available on the NI website. I am now hoping to extend the program to include spectral measurement using a USB spectrophotometer.

I have also written another VBA macro-enabled Excel workbook to import CSV files of multiple V-I-L sweeps to plot V-I-L curves, CIE(x,y) points, calculate current densities (mA/cm2) and efficiencies (cd/A, lm/W) and generate performance statistics (e.g. tables and Box-Whisker plots of cd/A @ 1mA/cm2 ) of groups of devices.

I am happy to provide source code if others would like to investigate the "limited, but cheaper" VBA method.

[vin31]

Hi, Could you please share your code. I want to communicate with Topcon BM-7A and use the data in LabVIEW code.

Thanks

Vinamra

[Plexonite]

Hi Vin,

Sorry I no longer have access to the code. How are you communicating with the instrument? Do you have the commands from the manufacturer? Sometimes they are not willing to share the commands because they want you to use their proprietary software.

E

[frankhl]

Hi Plexonite,

Can you provide other vis such as hysteresis and PDcurrent2Lum?

Thanks!

[nyc_(is_out_of_here)]

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@frankhl wrote:

Hi Plexonite,

Can you provide other vis such as hysteresis and PDcurrent2Lum?

Thanks!

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What part of "I no longer have access to the code" in Plexonite's post, do you not understand?

[Plexonite]

For the hysteresis I just used 2 ramp functions to generate the voltage sweep array. So you would have 4 controls: start voltage, ramp up voltage , ramp down voltage, and a hysteresis enable. The pdcurrent2lum was a simple linear calibration where the photo diode current, luminance, and voltage was collected at 10 mA/cm2 prior then since you know the luminance/pdcurrent ratio you can just multiply ratio to all the pd currents. We were able to do this because our photo diodes responded very linearly to our green and blue OLEDS. So depending on your color and luminance range you may have to do a different calibration procedure.