All solar photovoltaics drop in efficiencies with higher temperatures but it isn't the 45+ C you have to worry about but rather the heat from the sunlight striking the panels. There are hybrid systems which passes water in pipes attached to the back of the solar panels to cool the panels and preheat the water for solar thermal collectors. The difference between mono-crystalline and poly-crystalline are that mono-crystalline are more efficient and more costly to make.
