Physicists have discovered unusual electronic properties in a material that has potential to improve solar cell efficiency and computer chip design. The material has potential to improve solar cell efficiency and computer chip design. Researchers determined that a crystal made of bismuth, iron and oxygen can act as a reversible diode, and that diodes made from this material generate current when light falls on them. The material appears sensitive to light at the blue end of the spectrum, a property that could increase solar cell efficiency.