Since the intertwining of light and electron transfer enables life on the planet, it is no surprise that the same phenomenon can serve to empower materials[1] for service in the built environment. The inexpensive generation of electrical power from sunlight in a distributed manner will probably become possible with photoelectrochemical cells embedded in windows. From a chemical viewpoint, 1 can undergo photoinduced electron transfer (PET) with TiO2 and the resulting 1.+ can undergo further electron transfer with electrochemical relay I-, when the thermodynamic conditions are considered (Fig. 1). However, the efficiency of charge separation following PET in this and related cases is attributable to the nanostructured TiO2 matrix on which 1 is bound [2]. For instance, the electric current generation efficiency in sunlight is around 1000-fold higher for 1 in nanostructured TiO2 than on a chosen face of single-crystal TiO2 in its anatase form[3]. Besides the hugely increased surface area of this matrix (c.f. the single-crystal), it also avoids charge-depletion layers and local electric fields near the particles. Some of these window-cells will probably be adaptable to selfcleaning tasks as well, since photoelectrochemical cells are able to decompose organic compounds via redox processes [4].