The looks more like a photo cell (dusk to dawn) that a solar cell.
Also, that motion sensor should have a dusk to dawn sensor in it to prevent operation in daylight. (Or did you disconnect it.)
A lot of the fixtures/photo eyes sold over the years are not compatible with CFL/LED bulbs. Your problem may be your light bulbs. Your sensor may work fine with incandescent bulbs. Or buy a replacement sensor, but make sure before purchasing that the sensor is CFL/LED compatible.
Also, that motion sensor should have a dusk to dawn sensor in it to prevent operation in daylight. (Or did you disconnect it.)
A lot of the fixtures/photo eyes sold over the years are not compatible with CFL/LED bulbs. Your problem may be your light bulbs. Your sensor may work fine with incandescent bulbs. Or buy a replacement sensor, but make sure before purchasing that the sensor is CFL/LED compatible.