Apple is expected to unveil its biggest and most expensive iPhone on Wednesday as part of a lineup of three new models aimed at widening the product's appeal amid slowing sales growth.

If media leaks pan out, the newest additions to the iPhone lineup will make their debut at a scheduled company event in California.

Most of the buzz is swirling around a rumored iPhone that is supposed to boast a 6.5-inch OLED screen, up from 5.8 inches on the existing iPhone X. OLED is a step up from traditional LCD technology in offering a display without a backlight, so black is truly black rather than simply dark.

FILE- In this May 31, 2018, file photo customers enter the Apple store in New York. Apple is expected to unveil its biggest and most expensive iPhone yet on Wednesday, Sept. 12, along with two smaller, cheaper versions in an attempt to widen the product’s appeal amid slowing sales growth. (AP PhotoMark Lennihan, File)

FILE- In this May 31, 2018, file photo customers enter the Apple store in New York. Apple is expected to unveil its biggest and most expensive iPhone yet on Wednesday, Sept. 12, along with two smaller, cheaper versions in an attempt to widen the product’s appeal amid slowing sales growth. (AP PhotoMark Lennihan, File)

The iPhone X became the first mass-market smartphone to sell for $1,000, and now Apple is upping the ante again.