The analysts are citing supply chain sources spoken to during a trip to Asia.
"iPhone 8 design didn't sound 100% locked down but we believe the move is to a bezel-less design with screen sizes getting larger and curved edges in the original envelope. The IP8 moves to 5" (from 4.7") and the Plus moves to 5.8" (from 5.5")," the analysts write.
The mention of a 5-inch iPhone lines up with previous reports from Nikkei and KGI Securities analyst Ming-Chi Kuo.
The phones may stay the same size while the screens get bigger, thanks to less space around the screen.
Only the Plus model will have an OLED screen, a newer type of display technology with better color and deeper blacks, the analysts wrote. Most of the OLEDs will come from Samsung and LG, according to the report.
That's because of supply issues, they say, and the industry expects Foxconn's subsidiary Sharp to get its factories up and running in 2018.
The report also suggests that Apple's Force Touch feature may change to a "film-based solution" from the current "flexible PCB" technology that the iPhone 7 uses.
We're expecting Apple's iPhone 8 to be a major redesign to coincide with the 10th anniversary of the iPhone, and Barclays' predictions line up with what we've been hearing.