Is there a Y Combinator for single founders?
pg has said it's a negative, and it really is. The likelihood of a single founder company growing huge is smaller than if there's small team at the start, for all sorts of reasons (which pg and others have written about). But, if you've built something awesome, YC isn't going to say no just because you're a solo founder.
https://duckduckgo.com/?q=single+founder+y+combinator+compan...
Again, it's definitely a strike against you in the selection process (as it probably should be...I've started a company solo and I've started a company with a co-founder...the latter is clearly better), but it's not a deal-breaker.