Improvement of Performance of Organic Light-Emitting Diodes with Both a MoO3 Hole Injection Layer and a MoO3 Doped Hole Transport Layer

We improve the performance of organic light-emitting diodes （OLEDs） with both a MoO3 hole injection layer （HIL） and a MoO3 doped hole transport layer （HTL）, and present a systematical and comparative investigation on these devices. Compared with OLEDs with only MoO3 HIL or MoO3 doped HTL, OLEDs with both MoO3 HIL and MoO3 doped HTL show superior performance in driving voltage, power efficiency, and stability. Based on the typical NPB/Alq3 heterojunction structure, OLEDs with both MoO3 HIL and MoO3 doped HTL show a driving voltage of 5.4 V and a power efficiency of 1.41 lm/W for 1000 cd/m2, and a lifetime of around 0. 88 h with an initial luminance of 5268 cd/m2 under a constant current of 190 mA/cm2 operation in air without encapsulation. While OLEDs with only MoO3 HIL or MoO3 doped HTL show higher driving voltages of 6.4 V or 5.8 V and lower power efficiencies of 1.201m/W or 1.341m/W for 1000cd/m2, and a shorter lifetime of 0.33 or 0.60h with an initial luminance of around 5122 or 5300cd/m2 under a constant current of 200 or 216mA/cm2 operation. Our results demonstrate clearly that using both MoO3 HIL and MoO3 doped HTL is a simple and effective approach to simultaneoasly improve both the hole injection and transport efficiency, resulting from the lowered energy barrier at the anode interface and the increased hole carrier density in MoO3 doped HTL.

Synthesis and Photovoltaic Properties of Novel Porphyrin Derivatives

The porphyrin derivatives, 5,10,15,20-tetra（4-（N-pentane-carboxamide） phenyl） porphyrin（4 NC5-TPP）, 5,10,15,20-tetra（4-（N-dodecane-carboxamide） phenyl） porphyrin（4 NC12-TPP） and their zinc-complexes（4 NC5-TPPZn and 4 NC12-TPPZn）, have been synthesized. Their thermal properties and morphologies were investigated via thermal gravity analysis（TGA）, differential scanning calorimetry（DSC） and polarized optical microscopy（POM）. It was found that the 4 NC5-TPP was amorphous and the 4 NC5-TPPZn was crystalline at room temperature, while the 4 NC12-TPP formed the columnar liquid crystal and the 4 NC12-TPPZn showed the spherulite texture. The electron state density distributions and the optimum configuration of the porphyrin derivatives were calculated by chemical simulation. The electrochemical oxidation and reduction abilities of the porphyrin derivatives were studied by cyclic voltammetry（CV）. It was indicated that the porphyrin derivatives had the potential to develop organic photovoltaic（OPV） devices. Using the porphyrin derivatives as donor materials and the 3,4,9,10-perylenetetracarboxylic dianhydride（PTCDA） as the acceptor material, the OPV devices were fabricated. The device structure is ITO/porphyrin derivatives：PTCDA/Al. The relationship between the morphology and performance of OPV was studied. It was found that the crystalline morphology of the film was beneficial to improve the efficiency of the devices.