Ir led current at lower voltage

[Kajunbee]

I have a project to compare effects of different color light on solar panel output. What I built was a 5 sided box from 65mm x 65 mm panels with the panels facing in. On the inside of lid I mount various color leds to see which if any color gives greater output from panels. My question is about the expected current through led at lower than nominal voltage.
The first led I used was a 1.6 volt 20 ma IR led. The load on the panels was another identical IR led. The input voltage and current I measured was 1.60v at 20 ma. The output measurement to the load led was 1.25v at .40ma. Should the current measurement be this low at 1.25 volts are do you think it's a measurement error.

 

[KlausST]

Hi,

Usually the datasheet contains a V-I chart.
There you can find the answer on your own.

But it should be common knowledge not to "voltage drive" a LED.

It has already been discussed and documented in the internet - I assume - million times.

Klaus