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.

MoO_3/Ag/Al/ZnO intermediate layer for inverted tandem polymer solar cells

We report an MoO3/Ag/Al/ZnO intermediate layer connecting two identical bulk heterojunction subcells with a poly（3-hexylthiophene） and [6,6]-phenyl-C61-butyric acid methyl ester （P3HT and PCBM） active layer for inverted tan- dem polymer solar cells. The highly transparent intermediate layer with an optimized thickness realizes an Ohmic contact between the two subcells for effective charge extraction and recombination. A maximum power conversion efficiency of 3.76% is obtained for the tandem cell under 100 mW/cm2 illumination, which is larger than that of a single cell （3.15%）. The open-circuit voltage of the tandem cell （1.18 V） approaches double that of the single cell （0.61 V）.

Enhanced Field Emission from Large-Area Arrays of WlsO49 Pencil-Like Nanostructure

Field enhancement and field screening are two major factors affecting field emission performance of arrays of quasi one-dimensional nanostruetures. We have observed enhanced field emission from large-area arrays of W18O49 pencil-like nanostructure due to both the effects of high aspect ratio and enlarged spacing between neighboring nanostructures. These arrays may be grown on silicon substrates by the multi-step thermal evaporation process. The spacing of nanotip-to-nanotip between neighboring nanostruetures may be increased by adjusting the growth temperature. The arrays are observed to have a typical turn-on field as low as about 1.26 MV/m and a threshold field as low as about 3.39 MV/m, resulting in increasing field enhancement and decreasing field screening effect.

Organic Light-Emitting Devices with a LiF Hole Blocking Layer

We introduce a thin LiF layer into tris-8-hydroxyquinoline aluminium （Alq3 ） based bilayer organic light-emitting devices to block hole transport. By varying the thickness and position of this LiF layer in Alq3, we obtain an electroluminescent efficiency increase by a factor of two with respect to the control devices without a LiF blocking layer. By using a 10nm dye doped Alq3 sensor layer, we prove that LiF can block holes and excitons effectively. Experimental results suggest that the thin LiF layer may be a good hole and exciton blocking layer.

Electronic properties and tunability in graphene/3D-InP mixed-dimensional van der Waals heterostructure

InP solar cell is promising for space application due to its strong space radiation resistance and high power conversion efficient(PCE).Graphene/InP heterostructure solar cell is expected to have a higher PCE because strong near-infrared light can also be absorbed and converted additionally by graphene in this heterostructure.However,a low PCE was reported experimentally for Graphene/InP heterostructures.In this paper,electronic properties of graphene/InP heterostructures are calculated using density functional theory to understand the origin of the low PCE and propose possible improving ways.Our calculation results reveal that graphene contact with InP form a p-type Schottky heterostructure with a low Schottky barrier height(SBH).It is the low SBH that leads to the low PCE of graphene/InP heterostructure solar cells.A new heterostructure,graphene/insulating layer/InP solar cells,is proposed to raise SBH and PCE.Moreover,we also find that the opened bandgap of graphene and SBH in graphene/InP heterostructures can be tuned by exerting an electric field,which is useful for photodetector of graphene/InP heterostructures.

A NEW IMPROVED STRUCTURE OF DYE-SENSITIZED SOLAR CELLS WITH REFLECTION FILM

A new improved structure of dye- sensi- tized nanocrystalline solar cells (DSSC) for utilizing reflected light was introduced in this paper. Typical DSSC is based on a sandwich structure, which con- sists of photoanode, electrolyte and cathode. For the improved structure of DSSC in this paper, a sliver reflection film was attached to the back of transparent conducting glass of cathode. In this way, the residual light passing through photoanode was reflected to it to be used again. The photocurrent-voltage charac- teristics of DSSC fabricated by two different thickness of TiO2 film were measured to illustrate the effects of utilizing reflected light. As a result, the improved DSSC with reflection film exhibited higher photocur- rent and solar-to-electric conversion efficiency than DSSC without reflection film.

A novel solar cell fabricated with spiral photo-electrode for capturing sunlight 3-dimensionally

A novel solar cell fabricated with spiral photo-electrode for capturing sunlight 3-dimensionally (3D-cell) is proposed in this paper. We studied its performance both in solar simulator and in nature sunlight. Spiral photo-electrode of 3D-cell can receive sunlight from all directions and therefore can track the sun passively. And it is much insensitive to solar azimuth angle and shade. In addition, it increases the area to obtain scattered sunlight and reflected light. Compared with the dye-sensitized solar cells using sandwich structure, it would be more advantageous in the sealing technique.