Devices and methods for absorbing light

A light-absorbing device comprising a series of photon-absorbing semiconductor substructures, the device comprising:

• a first semiconductor substructure providing first and second energy states, the difference between the first and second energy states being such as to cause an electron to be promoted from the first energy state to the second energy state upon absorption of a photon of a first energy;
• and
• a second semiconductor substructure providing third and fourth energy states, the third energy state being arranged to receive the electron from the second energy state, and the difference between the third and fourth energy states being such as to cause the electron to be promoted from the third energy state to the fourth energy state upon absorption of a subsequent photon of a second energy;
• wherein the third energy state has a lower energy than the second energy state, such as to cause the electron to dissipate energy as it passes from the second energy state to the third energy state.