▁K all mann ▁and ▁Pope . ▁They ▁found ▁that ▁a ▁hole ▁current ▁can ▁flow ▁through ▁an ▁anth rac ene ▁cry stal ▁contact ed ▁with ▁a ▁posit ively ▁bi ased ▁electro ly te ▁containing ▁i od ine ▁that ▁can ▁act ▁as ▁a ▁hole ▁inject or . ▁This ▁work ▁was ▁stim ulated ▁by ▁the ▁earlier ▁discovery ▁by ▁Ak am atu ▁et ▁al . ▁that ▁a rom atic ▁hydro car b ons ▁become ▁conduct ive ▁when ▁bl ended ▁with ▁mole cular ▁i od ine ▁because ▁a ▁charge - trans fer ▁complex ▁is ▁formed . ▁Since ▁it ▁was ▁readily ▁realized ▁that ▁the ▁cru cial ▁parameter ▁that ▁controls ▁injection ▁is ▁the ▁work ▁function ▁of ▁the ▁electro de , ▁it ▁was ▁straightforward ▁to ▁replace ▁the ▁electro ly te ▁by ▁a ▁solid ▁met all ic ▁or ▁sem icon duct ing ▁contact ▁with ▁an ▁appropriate ▁work ▁function . ▁When ▁both ▁electrons ▁and ▁holes ▁are ▁inject ed ▁from ▁opposite ▁contacts , ▁they ▁can ▁re comb ine ▁radi atively ▁and ▁emit ▁light ▁( elect rol um ines c ence ). ▁It ▁was ▁observed ▁in ▁organ ic ▁cry st als ▁in ▁ 1 9 6 5 ▁by ▁S ano ▁et ▁al . ▁ ▁In ▁ 1 9 7 2 , ▁research ers ▁found ▁met all ic ▁conduct ivity ▁in ▁the ▁charge - trans fer ▁complex ▁T TF - TC N Q . ▁Super con duct ivity ▁in ▁charge - trans fer ▁complex es ▁was ▁first ▁reported ▁in ▁the ▁Be ch ga ard ▁salt ▁( TM TS F ) 2 PF 6 ▁in ▁ 1