Reusable mass-sensor in manufacture of organic light-emitting devices

Apparatus for depositing an evaporated or sublimed organic layer onto a structure which will form part of an organic light-emitting device, comprising:

• a) a housing defining a chamber and a pump connected to the chamber for reducing the pressure therein;
• b) a source for receiving organic material to be evaporated or sublimed and means connected to the source for adjusting the temperature thereof to control the rate at which the organic material is evaporated or sublimed;
• c) means for positioning the structure so that such structure is located spaced from the source in a deposition zone;
• d) a first movable sensor of a plurality of movable sensors positioned in the deposition zone for receiving organic material from the source at the same time such organic material is deposited onto the structure;
• e) electrical means connected to the first movable sensor and responsive to the thickness of the organic material deposited on the sensor for adjusting the temperature control means to control the rate of deposition and the thickness of the organic layer formed on the structure;
• f) means for moving the first sensor out of the deposition zone and means for removing in whole or in part organic material deposited on the sensor so that such sensor can be reused in the deposition zone;
• and
• g) means for moving a second movable sensor of the plurality of movable sensors into the deposition zone and electrical means connected to such second sensor.