There's a related question: In space can the difference in temperature between the inside and outside, provide useful energy?
The problem with that one is that it relies on the concept of "hot inside" and using space as the heat sink - while there are sources (like the Sun) which would pretty much heat up the "outside" more than the "inside", and generally a range of other problems.
Now, there should be a much simpler way of exploiting heat transfer: Let's take a pad of Peltier cells, with the side exposed to the Sun, with highly absorbent coating, and an array of radiators of high emmissivity on the "dark side".
The basic problem on Earth is the "ambient temperature" - about as much heat as is radiated out of the "cooled side" is returned to it by radiating Earth, and balanced out by convection+conduction of heat from air. In space, there's Cosmic Microwave Background (CMB) which, if I understand correctly, is fairly weak. There is no convection but radiation is fairly efficient. That means considerable amounts of heat could be transferred from the Sun side to the "outer space" side, at least as long as we remain relatively near to the Sun.
Of course such heat transfer could be exploited through any energy source that exploits heat transfer - like a Peltier cell, or even if you're willing to go that far, through a Stirling engine.
Now, how would such systems fare against "tried old" photovoltaic cells? Could someone throw some numbers at me, comparing what we could expect from the same surface/mass/price of one versus the other?