EmuNations

The "PlayStation Portable Simulator Suitable for Playing Portably" is a multi-platform, open-source emulator written in C++ with the aim of speed and portability. It can run PSP games in full HD resolution with upscaling textures to reduce bluriness and most games are playable. Its development is ongoing and still in beta state, though does have a Switch port and libretro core.

JPCSP is an open-source PlayStation Portable emulator written in Java. It requires Java Runtime environment to be installed.  it can reach 100% PSP speed on a lot of commercial games and is still being actively developed. That said, JAVA Runtime has a history of security breaches and tends to be a little slower than C-based emulators. All in all, it's a really intresting approach to emulation.