There are many fan theories going around Han Solo’s death, One them being that Han Solo killed himself. Remember, How in ‘Harry Potter : Half Blood Prince‘ Albus Dumbledore had asked “Severus Snape” to kill him. As killing Dumbledore would prove Snape’s allegiance toward Lord Voldemort, and help in being undercover. Similarly, there could a same possibility in ‘Star Wars : Force Awakens‘, where Han Solo wanted Kylo Ren to prove his allegiance towards Supreme Commander Snoke and the Dark Side.
Here is an interesting Fan Theory :
“It was Han Solo, who activated the lightsaber, not Ben (Kylo Ren). “I know what I have to do but I don’t know if I have the strength to do it” “will you help me” Han: “yes anything” Kylo pulls out his lightsaber holds it in both hands. Han reaches down grasp the center of it. We just see their faces but notice they aren’t struggling. Lightsaber activates and goes through Han, Kylo looks startled for a moment and says “thank you” Han touches his son’s face and falls into the abyss.
Kylo/Ben journey to the dark side required him to kill his father. Han knew this and knew that Supreme Commander Snoke would kill his son if he failed this task. By Han activating the lightsaber himself, Kylo can still go back to Snoke and report that the deed is done but the fact is that it wasn’t really him, who killed his father. This ensures there will always be a smidge of light left in him that can never be snuffed out. Eventually, Han’s sacrifice will succeedin his promise to Bring their son home .”