How does a screen work?

LCD on paper you see lots of drawbacks, in practice modern state of the art LCD for TV is pretty damn good. We will soon have RGB LED Backlight LCD with WHVA+ Panel that is about as wide angle as IPS, 95%+ REC 2020 colour, and 1-2ms response time.

Phosphorescent blue OLEDs should reduce current OLED display energy usage by 20-30%. But it still seems to be way off for phones and mass usage.

I think it's fairly common for technologies to get really good just as they're becoming obsolete. Vacuum tubes, CRTs, optical disks, photographic film... in fact, they're often in some respects better than the early generations of the technology that replaces them.

But OLEDs just have too many advantages where it actually matters. Much lower power consumption, physically more compact (no need for backlight layers), etc.

None of that really helps LCDs primary downsides of poor contrast ratio and relatively high energy consumption. Backlit displays will always inherently score worse on these metrics vs self emissive displays.

You might add ICE cars to that list. All kinds of cool stuff being developed around small turbocharged engines and other efficiency gains, excellent transmissions, etc.

For me, OLEDs fall into a category exemplified by Anton Gudim's "YES, BUT" comic series.

YES, OLEDs consume less power, offer truer color reproduction, and are physically more compact.

BUT, they are prone to CRT-like burn-in.

SSDs, the same thing.

YES, SSDs are much faster and immune to mechanical failure.

BUT, they tend not to last as long as HDDs due to limited write cycles, and their price per GiB is still much higher.

The energy efficiency of LCDs is very good, typically better than OLED screens, except on very dark content.

>downsides of poor contrast ratio

In terms of TV. LCD have higher peak brightness. The Sony Bravia 10 will be out soon, hopefully it will showcase the world what LCD could be.

Not to mention cheaper at larger size panel.

LCDs as a transmissive display technology work by emitting a bunch of photons and then selectively filtering some out to achieve the desired color / pixel brightness. Any filtered photon is wasted energy, this is inherent to the display technology and is not limited to dark content, just exacerbated by it.

Given that, all things equal there is no way for LCD to equal the efficiency of a self emissive display, at best it's a question of when will the luminous efficiency of OLED exceed that of white/blue backlight LEDs... and honestly we're likely already at or past that point.

peak brightness is not contrast. If anything higher peaks mean worse contrast, even for systems with local dimming zones due to bleed between zones / gradients in display content which do not align with backlight zones.

> Given that, all things equal there is no way for LCD to equal the efficiency of a self emissive display

The backlight LEDs are just much more efficient than OLEDs. The power consumption of TVs / monitors is a well known quantity.