We incorporated an additional p-type organic semiconductor layer (APL) between the anode and the phthalocyanine layer, which is an indispensable p-type semiconductor layer (IPL) in forming a p/n junction with a fullerene C 60 layer. We used two thiophene/phenylene co-oligomers as the APL. The incorporation increases the short-circuit current density (J SC ) and enhances incident photon-current conversion efficiency (IPCE) over the wavelength region where the APL shows strong absorption.Combined dependence of the APL/IPL implies that Förster resonance excitation transfer is the main factor in J SC and IPCE enhancements. We demonstrate clearly that the 'positive' hole injection barrier at the interface between the APL and the IPL impacts the smooth transportation of holes to the indium-tin-oxide anode. However, the small positive hole barrier of 0.1 eV has no noticeable influence on the fill factor of the current density vs. voltage characteristic under photoirradiation, or on those devices

We demonstrated important changes produced on the modulation frequency of hybrid organic–inorganic light‐emitting diodes to examine the applicability as a light source for visible optical communications. The fabricated device structure was 4,4′‐bis[N ‐(1‐napthyl)‐N ‐phenyl‐amino]biphenyl/4,4′‐(bis(9‐ethyl‐3‐carbazovinylene)‐1,1′‐biphenyl:4,4′‐bis[9‐dicarbazolyl]‐2,2′‐biphenyl/ZnS/LiF/MgAg. This device showed an improvement in the modulation frequency using ZnS instead of an organic material, tris(8‐hydroxyquinoline)aluminum. A maximum cutoff frequency of 20.6 MHz was achieved.magnified image(© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)