it’s not a schottky diode, it’s just a plain vanilla diode, although I’m pretty hazy on the differences between the two. The important difference is that the plain diode drops more voltage than the schottky, which is what we want, even though that’s often a bad thing I’m told 
The circuit is Battery>diode>LED>driver>battery. So all the diode does is increase the effective Vf of the LED, so there’s less voltage drop across the driver. It doesn’t affect efficiency in any way that I can understand, the main point is to reduce some of the burden on the 7135 chips. The higher the voltage drop and current draw per chip, the higher the power that needs to be dissipated as heat. As they get hotter they either get less efficient, shut off independently or die, none of which are good things. So all a diode does is add another place from which voltage can be burned off as heat, so there’s less to burn off in the driver.
You can do a similar thing with a resistor in series with the LED, but for my application the voltage drop across it would change too much with current, so getting the right resistance value for one extreme would make it inappropriate at the other.
These
http://www.ebay.com/itm/180847140820?ssPageName=STRK:MEWNX:IT&\_trksid=p3984.m1439.l2649
were what I bought. I have some spare if anyone wants one, although for a buck you could just get 10 of your own From what I remember these were what suited my voltage drop/ current rating/ size requirements at the time, although exactly how I came to that model I can’t quite remember. Here Driver Matching was the thread where I learned about diodes 
I took pictures (although not very informative ones) but my camera’s at home, so I can upload some tomorrow if that helps?
edit: the end with the band points towards the LED. Very easy to figure it out - wire it up the wrong way and the LED won’t light