iPhone

I am so sorry for your loss. Unfortunately, without knowing his phone’s lock code nothing can be accessed on the phone, and Apple (nor anyone else) has any way of recovering the phone’s lock code. If he synced the photos to iCloud they can be accessed using his Apple ID and password. So if he recorded these somewhere you can log in to https://icloud.com and download the photos from there. Similarly if he had a Mac those photos can be found in the Photos app on the Mac, or it it was Windows and he installed iCloud for Windows they would be there.

Other options, if he did not use iCloud photos:

• If he backed up the phone to his computer they will be in the iTunes backup, which can be access with 3rd party tools
• If he shared the photos anyone he shared them with should be able to find them on their computer
• If he synced them to an online photo service like Google Photos or Shutterfly and you have is credentials for these services they can be recovered from there.

Without knowing the passcode to the iPhone, I don't know of any way. With a death certificate and a will, Apple can erase the iPhone ()pitting not in a "factory fresh" state), but they cannot give your access to it.

How to request access to a deceased family member's Apple accounts - Apple Support

Bring the iPhone and appropriate paperwork (death certificate, proof of iPhone ownership) to an Apple Store and seek assistance there.

You will need to know the passcode that was used to unlock the phone when it is turned on. Without that, there is no way to access the phone.