Cathode Interfacial Modification In Organic Optoelectronic Devices

This thesis focuses on cathode interfacial modification and interfacial physicsin the organic optoelectronic devices. Main contents include:1. Highly efficient organic light-emitting diodes (OLEDs), polymerlight-emitting diodes (PLEDs) and polymer solar cells (PSCs) have been fabricatedusing alkali metal salts (LiF, NaF, CsF and Cs2CO3) as a cathode interlayer. InOLEDs and PLEDs, CsF as a cathode interlayer presents the highest luminousefficiency and power efficiency in the four alkali metal salts. It is apparent thateffect of LiF, NaF, CsF and Cs2CO3as a cathode interlayer on device performance isdifferent and efficiency sequence of corresponding devices is CsF Cs2CO3NaF>LiF. In particular in PLEDs with Poly(p-phenylene vinylene)(P-PPV)as an emitter, introduction of CsF as a cathode interlayer gives rise to a maximumluminous efficiency up to17.8cd/A which is nearly4times of luminous efficiencyof device with LiF as a cathode interlayer. When LiF is selected as a cathodeinterlayer in PSCs with Poly(3-hexylthiophene)（P3HT）：Phenyl-C61-butyric acidmethyl ester（PC61BM） as an active layer, PCE can reach4.12%while PCE valuesof PSCs with NaF, Cs2CO3and CsFas a cathode interlayer are3.72%,3.55%and3.2%, respectively.PSCs with polymer thieno[3,4-b]-thiophene/benzodithiophene(PTB7):[6,6]-phenyl C71-butyric acidmethyl ester (PC71BM) as an active layer havebeen fabricated using water/alcohol organic molecule MetallophthalocyanineDerivative2. A novel cathode interlayer, water/alcohol organic moleculemetallophthalocyanine derivative (VOPc(OPyCH3I)8) has been synthesized andsuccessfully utilized in the PSCs based on polymer thieno[3,4-b]-thiophene/benzodithiophene (PTB7):[6,6]-phenyl C71-butyric acidmethyl ester (PC71BM) as anactive layer. Compared to the two control devices, a simultaneous enhancement inVOC, JSCand FF of the PSC with VOPc(OPyCH3I)8as a cathode interlayer has been observed. As a result, a PCE of8.12%for the working areas of22mm2and a PCE of7.23%for the working areas of44mm2have been achieved. They are comparablewith the best values of PCE of the PSCs reported currently. Moreover a PCE of PSCwith VOPc(OPyCH3I)8as a cathode interlayer is higher than one of PSC with PFN asa cathode interlayer in this study. It indicates that VOPc(OPyCH3I)8is a newpromising candidate as a good cathode interlayer for highly efficient PSCs. Inaddition, we also carried out dark current density-voltage, external quantum efficiency(EQE) spectra, electron mobility, ultraviolet photoemission spectroscopy (UPS), AFMand contact angle measurements in order to provide some reasonable explanation. Sofar we propose that interface dipole maybe dominating working mechanism ofVOPc(OPyCH3I)8as a cathode interlayer in PSCs.