Apple has long been rumored to be adopting Sharp’s sophisticated IGZO display technology for iPhones and iPads, but the reported ongoing yields issues have prevented it from making the switch over concerns on maintaining a minimum level of capacity.

At the same time, it hasn’t gone unnoticed that the iPad Air achieves the same 10-hour battery life (and 24-hour LTE hotspot performance) in spite of packing in a powerful 64-bit A7 processor and, more importantly, a much smaller battery than its predecessor, 32.9 Whr versus 43 Whr for the iPad 4.

Now, one of the benefits of using IGZO display technologies is vastly reduced power consumption. So, has Apple switched to IGZO panels for the iPad Air or not?

To find that out, Eric Slivka of MacRumors spoke to one guy who knows these things inside out, Dr. Ray Soneira of DisplayMate Technologies.

Soneira suspects Apple is using IGZO panels for the iPad Air based on the 57 percent improvement in power efficiency of the iPad Air’s display versus previous iPads.

Such a marked improvement simply is not possible with the amorphous silicon (a-Si) compounds used in previous iPads. Conveniently, indium gallium zinc oxide (IGZO) semiconductor materials could explain the iPad Air’s power-efficient display.

In addition to rendering deeper blacks, more vibrant colors and providing an all-around sharper image on ultra-high resolution displays, IGZO panels are said to consume only a fraction of the power versus the traditional LCD technology, as in about ten percent of the LCD’s power draw.

Also, bear in mind the display is by and large the iPad’s most power-hungry component.

Therefore, had Apple kept the traditional LCD around, it could only have gotten away using the smaller battery for the iPad Air while maintaining the ten-hour battery life by switching to a much more power-efficient screen.

Enter IGZO, which allows for the iPad Air’s brighter image with higher contrast and less refractions. Here’s a passage from Soneira’s display shootout comparing the iPad Air’s display to that of the Kindle Fire HDX 8.9 and the Google Nexus 10 (emphasis mine):

The most important under the hood display improvement is the switch from a-Si amorphous Silicon LCDs up to a much higher performance IGZO LCD backplane. The switch to IGZO produces an impressive 57 percent improvement in display power efficiency from previous Retina Display iPads – so the iPad Air doesn’t get uncomfortably warm like the earlier iPads.

Even more to the point, an IHS iSuppli teardown analysis has revealed that the iPad Air uses fewer LEDs versus its predecessor. These power-hungry modules provide the backlighting for the screen and the iPad Air achieves the same level of brightness with just 36 LED lights versus 84, or less than half the LEDs than the iPad 3.

The traditional LCD IPS screen on previous iPads definitely requires way more than 36 LEDs in order to push the light between the densely packed pixels. But not IGZO.

Soneira expects Apple will adopt IGZO panels for the upcoming iPad mini with Retina display, even more so given its higher pixel density on the 40 percent smaller canvas. Put simply, an a-Si screen would be infeasible for a Retina display at that size.

For the Kindle Fire HDX 8.9’s better-than-iPad-Air-screen, Amazon utilizes the more complicated – but also better performing and more power-savvy – low temperature polysilicon (LTPS) technology.

That tech, Soneira cautioned, doesn’t scale well to support Apple’s volume requirements that now approach a hundred million tablet panels on an annual basis.

IGZO also offers a more natural transition for display manufacturers, as they can in many cases simply upgrade their existing equipment from current a-Si production, while moving to LTPS would require a complete change in production. IGZO is also just the first of a number of metal oxide semiconductors that show promise for improved display performance, pointing to solid opportunities for the technology to continue to evolve.

Before wrapping up, Apple says it has managed to achieve the iPad Air’s 24 percent reduction in overall volume by shaving fractions of millimeters off many components: the cover glass is 17 percent thinner, the touch sensor is as much as 70 percent thinner, with the Retina display itself having shaved of 20 percent off its overall thickness.

And if you believe the rumors based on supply chain chatter, apparently Sharp has finally managed to commercialize mass-production of IGZO panels for smartphones and will begin churning them out at its Kameyama Plant Number 2 before the end of 2013.

Who wants an iPhone 6 with an IGZO screen?