(a) Schematic of a field-induced organic light emitting board (OLEB) based on a parallel alternating-current electroluminescent (AC EL) device for visualizing fingerprint. (b) A photograph of an electroluminescent (EL) image of fingerprint pattern obtained by gentle contact of a finger on an OLEB. The scale bar is 5 mm. (c) A plot of device current as a function of the applied voltage on finger contact at 100 kHz. (d) The variation of device current under repeated events of finger touching and de-touching. (e) Reliable variation of the device current as a function of the number of finger touching events on a SiO2 insulating layer of the OLEB. (f) Photographs of EL images of fingerprint patterns obtained from OLEBs with green and blue fluorescent polymers under gentle finger contact. The scale bar is 5 mm. (g) Photographs of a mechanically flexible OLEB and a fingerprint EL image obtained from the flexible EL board. The scale bar is 5 mm. (h) Schematic of an OLEB consisting of 3 × 3 arrays of parallel-type Indium tin oxide (ITO) electrodes. (i) Photographs of an OLEB with arrays of parallel-type ITO electrodes with position recognition of a finger touch. The scale bar is 5 mm.