In Diablo 2, if you wanted a higher difficulty in single player, you could type
/players 8 to make the game scale the difficulty, experience, and drops to what it'd be if there were 8 players in game.
Does Diablo 3 have an equivalent? I was not able to find anything in the D3 FAQ, so I would suspect it does not. Are there any methods for increasing the difficulty/exp/drops other than playing at a higher difficulty level?