MELl /i\ CALVIN 339 



tion oi the electrons in the o-(|uinone negative ion up to an excited 

 oihiial which (an then be tianslenecl into the lowest unoccupied 

 orbital ol the phthalocyanine crystal (a conduction orbital) . This, 

 then, is a relatively mobile electron which can rapidly find and 

 neutralize the conductivity holes in the phthalocyanine lattice, leading 

 to a decrease in conductivity. These represent the principal processes 

 shown in Fig. 16. 



rr® 



hv (7000) 



Pc 0-Q Pc o-Q" 



hv(4000) 



• > — o • 



• • — —m — • 



• » — • — • 



— • — » 



Pc Pc 



Pc O-Q" 



Fig. 18. Diagiammatic molecular orbital representation of a solid matrix of 



phthalocyanine with o-Q. 



Fig. 19 shows the actual separation of charge that can be accom- 

 plished in this model system if it is constructed properly. Here is 

 shown a matrix of phthalocyanine, on the surface of which lies an 

 o-quinone layer. There will be some negative charge trapped in the 

 o-quinone (acceptor) layer, and the positive charge will remain in 

 the phthalocyanine (donor) layer. This will induce a polarization 

 in the pair of electrodes between which the double layer is placed. 

 The polarization will be increased by shining light absorbed by 

 phthalocyanine on the double layer, in which case there will be an 

 additional accumulation of negative charge in the quinone and an 



