Photosensitizers absorb light (hν) and transfer the energy from the incident light into another nearby molecule either directly or by a chemical reaction.  Upon absorbing photons of radiation from incident light, photosensitizers transform into an excited singlet state. The single electron in the excited singlet state then flips in its intrinsic spin state via Intersystem crossing to become an excited triplet state. Triplet states typically have longer lifetimes than excited singlets. The prolonged lifetime increases the probability of interacting with other molecules nearby. Photosensitizers experience varying levels of efficiency for intersystem crossing at different wavelengths of light based on the internal electronic structure of the molecule.