I found that on mine, I also have the sunglasses issue. I have prescriptions, and even though I also have Transitions lenses in my regulars, I like my polarized sunglasses for well, sunny days. And if I turn my phone to landscape mode, I lose the display. So I either have to turn my head to match (which I'm sure in itself would be a funny picture....), take the photo in portrait instead and lose the wider view, put on my regulars and give them a moment to adjust so I don't get blinded by sunlight... or what I tend to do, is to turn the phone, position my finger where the shutter button is, then turn it back, and take a series of pictures hoping at least one comes out in focus. I'll review them later and delete unwanteds.
That aside though, I find that even in very direct sunlight, when my phone is on max brightness (at the expense of battery life), I can still see, even with the polarized on that still toys with certain angles upright. With my regular lenses on, I have no issues at all. It might be a little washed out so I can't see EVERY detail, but it's certainly functional enough for my tastes. Otherwise, it's shielding with your hand/body, or ducking into the cabin a foot to see.
If you're having issues, and it's a decent enough phone, double check the brightness settings. Might be better to manually adjust to full brightness instead of letting the auto setting work. Some phones are a little pickier about it. Mine has a setting on auto where I can limit the max brightness it will go to, as a battery saver, i.e. 80% is the max it'll go (or whatever I set it). So when I'm outside, I make sure to switch the auto off and manually go full bright.
