Fig. 1. Schematic diagram of the preparation of OLED emitting layer film by inkjet printing

Fig. 2. Film forming control process

Fig. 3. Principle of drop volume measurement^［23］

Fig. 4. Droplet volume control

Fig. 5. Droplet landing position control.（a）Normal landing position range；（b）Offset measurement；（c）Array formed by multiple nozzles printing；（d）Wrong landing position of droplets printed by abnormal nozzles.

Fig. 6. Motion process of nozzle and substrate

Fig. 7. Patterned schematic

Fig. 8. Inkjet printing equipment.（a）Overall appearance；（b）Inside the inkjet printer.

Fig. 9. Droplet volume measurement results

Fig. 10. Droplet landing position measurement results.（a）Before compensation；（b）After compensation.

Fig. 11. Droplets deposition.（a）Droplets array；（b）Printing by droplets unmixing method；（c）Printing by droplets mixing method.

Fig. 12. Morphology of film in the pixel pit

Fig. 13. Measurement results of film thickness in pixel pits

Fig. 14. OLED device lighting results.（a）Droplets unmixing；（b）Droplets mixing.