We have developed a device for performing neutron scattering experiments with simultaneous irradiation by light at low temperatures. The light source is a halogen lamp which yields broad bands of wavelengths between 400 nm and 1 000 nm by using appropriate filters. The light is guided by a series of lenses to the sample which is mounted in a cooling system. A mechanical chopper may be inserted into the light beam in order to create light pulses with frequencies between 0.05 Hz and 5 Hz, and the neutron counts resulting from the dark and light experiments are separately stored. Our device has been used to study the light-induced dynamical behaviour of photosynthetic chlorophyll systems by neutron spectroscopy