Semiconductor nanocrystals exhibit strong quantum sized effects. They may prove to be important building blocks for solar cells that exploit quantum effects explicitly. While quantum effects can easily be used to control the initial events of light absorption and possibly the earliest events of electron relaxation, the issue of facile transport in nanocrystals solar cells remains as a problem. This talk will describe two limiting types of nanocrystal solar cells, distinguished by the relationship between the size of the nanocrystals and the bulk exciton diameter. In the case where the nanocrystal is very much smaller than the bulk exciton, it is possible to make an ordered array of the nanocrystals and to investigate the possibility that mini-bands form when the particles are placed in the array. In that case, the transport between the particles may be facile. In the second case, all the elements of the solar cell can be built into a single nanocrystal, so that the charges need not hop between nanocrystals in order to be harvested. Practical examples of these two types of solar cells will be discussed.