Developing economic and green methods to supply our future energy needs is perhaps the grand challenge of our time. Due to its abundant and distributed supply, solar energy may play a key role in this revolution. However, limitations in cost and efficiency have hindered solar photovoltaic energy conversion from supplying a large fraction of our energy. The seminar will focus on our progress towards solving the key challenges to decrease the cost and increase the efficiency of photovoltaic energy conversion by developing new nanomaterials and devices. In particular, I will discuss recent developments on a new low-cost route to solar cells based on colloidal semiconductor nanocrystal inks and on a new nanofabrication method for forming solar cells based on semiconductor quantum wire arrays. The materials for the latter are made using self-assembly and have the potential to take advantage of photophysics that can exceed the Shockley-Queisser limit (33%, the upper limit of energy conversion for a conventional single junction solar cell).