Just days after announcing the launch of major expansions in New York state, the San Mateo-based solar company SolarCity has filed for an IPO in excess of $200 million. Having already received more than $1.5 billion in funding from a variety of high profile companies including Google, PG&E, and U.S. Bancorp, SolarCity is betting on the success of its business model to appeal to stock investors eager to snatch up a slice of the potentially lucrative solar pie.