Complex sentence: This is because the phosphor compounds which emit light to produce images lose their luminance with use; uneven usage results in uneven light output over time and in severe cases can create a ghost image of previous content.
Split into simpler sentences: This is because the phosphor compounds which emit light to produce images lose their luminance with use. Uneven usage results in uneven light output over time, and in severe cases can create a ghost image of previous content.