. ▁ ▁The ▁discovery ▁by ▁K all man ▁and ▁Pope ▁p aved ▁the ▁way ▁for ▁applying ▁organ ic ▁sol ids ▁as ▁active ▁elements ▁in ▁sem icon duct ing ▁electronic ▁devices , ▁such ▁as ▁organ ic ▁light - em itting ▁di odes ▁( O LED s ) ▁that ▁rely ▁on ▁the ▁recom bin ation ▁of ▁electrons ▁and ▁hole ▁inject ed ▁from ▁" oh mic " ▁electro des , ▁i . e . ▁electro des ▁with ▁un limited ▁supply ▁of ▁charge ▁carri ers . ▁The ▁next ▁major ▁step ▁towards ▁the ▁techn ological ▁explo itation ▁of ▁the ▁phenomen on ▁of ▁electron ▁and ▁hole ▁injection ▁into ▁a ▁non - c ry st all ine ▁organ ic ▁sem icon duct or ▁was ▁the ▁work ▁by ▁Tang ▁and ▁Van ▁S ly ke . ▁They ▁showed ▁that ▁efficient ▁elect rol um ines c ence ▁can ▁be ▁generated ▁in ▁a ▁v apor - de pos ited ▁thin ▁am orph ous ▁bil ayer ▁of ▁an ▁a rom atic ▁diam ine ▁( T AP C ) ▁and ▁Al q 3 ▁sand wich ed ▁between ▁an ▁ind ium - t in - ox ide ▁( IT O ) ▁an ode ▁and ▁an ▁M g : Ag ▁c ath ode . ▁Another ▁mil estone ▁towards ▁the ▁development ▁of ▁organ ic ▁light - em itting ▁di odes ▁( O LED s ) ▁was ▁the ▁recognition ▁that ▁also ▁conjug ated ▁polym ers ▁can ▁be ▁used ▁as ▁active ▁materials . ▁The ▁efficiency ▁of ▁O LED s ▁was ▁greatly ▁improved ▁when ▁real izing ▁that ▁ph osph ores cent ▁states