An OLED phone screen.

OLED (organic light-emitting diode) screens are capable of creating higher-quality images, mainly because they're able to produce significantly deeper black levels compared with LCD (liquid crystal display) screens. 

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This means that when you look at an OLED phone screen, colors pop and dark details are more clearly defined. You'll find these screens on more expensive models, such as the Samsung Galaxy S9, $620, and the iPhone X, $1,000.

But OLED phone screens can suffer from burn-in, or traces of old images that linger on the screen. And when displaying brighter images, such as a sunny sky, an OLED phone screen may dim, says Richard Fisco, CR's head of smartphone testing.

"Even so, OLEDs are certainly the best looking screens out there," says Fisco. But phones with LCD screens still offer smooth, crisp high-resolution displays at budget-friendly prices, such as the LG G6, $500.

Editor's Note: This article also appeared in the November 2018 issue of Consumer Reports magazine.