3D photovoltaic (PV) devices employ a 3D structure to improve photoelectric efficiency by increasing the amount of light captured by the light-absorbing material in the PV cell or panel. By comparison, conventional solar cells consist of a 2D planar diode structure. By utilizing a 3D design, the surface area available for light absorption is increased, and some designs incorporate nanostructures such as wells, towers or nanotubes intended to trap photons, increasing the proportion that impart their energy to the PV cell. Once the sunlight strikes the 3D solar panel, the 3D design will trap the sunlight and help bounce the photons (many times) until they have been fully converted into electrons and hence usable electricity. 3D solar cells may also include features intended to reduce the rate of recombination of electron-hole pairs. 3D PV technology can also improve solar cell performance by reducing light reflection. 3D PV technology has the potential to produce much-higher-efficiency PV cells, panels and systems; however, it is still too early to determine what the real-world efficiency will be. The key challenge for commercialization of this technology will be developing a low-cost manufacturing process that can translate the efficiency gains into lower-cost solar electricity.