All the cells in one string (i.e. all the cells in series, connected positive to negative terminal) need uniform sunlight. Otherwise some cells can go into reve

All the cells in one string (i.e. all the cells in series, connected positive to negative terminal) need uniform sunlight. Otherwise some cells can go into reverse bias and dissipate the power of the other cells in the string. This happens, for example where there is uneven shade, or dirt on the array.