Photoemission Spectroscopy Characterization of Attempts to Deposit MoO 2

Attempts to deposit molybdenum dioxide (MoO2) thin films have been described. Electronic structure of films, deposited by thermal evaporation of MoO2 powder, had been investigated with ultraviolet photoemission and X-ray photoemission spectroscopy (UPS and XPS). The thermally evaporated films were found to be similar to the thermally evaporated MoO3 films at the early deposition stage. XPS analysis of MoO2 powder reveals presence of +5 and +6 oxidation states in Mo 3d core level along with +4 state. The residue of MoO2 powder indicates substantial reduction in higher oxidation states while keeping +4 oxidation state almost intact. Interface formation between chloroaluminum phthalocyanine (AlPc-Cl) and the thermally evaporated film was also investigated

High Efficiency Organic Light Emitting Devices for Lighting

Incorporate internal scattering layers and microlens arrays in high efficiency OLED to achieve up to 70% EQE

Department of Energy Office of Energy Efficiency and Renewable Energy Solid State Lighting Core Technologies

The project objective is to demonstrate high efficiency white emitting OLED devices with a target luminous efficiency between 100 1m/W and 150 1m/W with integrated microcavity structure and down conversion phosphors. The main focus of this work will be on three areas: (1) demonstration of a 2X reduction in OLED device operating voltage by employing the appropriate dopants in the carrier transporting layers; (2) demonstration of a 3X light out-coupling efficiency enhancement by incorporating microcavity structure in the OLED devices; and (3) demonstration of a 2X down-conversion efficiency enhancement (from blue to white) using phosphors

Organic and Inorganic Blocking Layers for Solution-Processed Colloidal PbSe Nanocrystal Infrared Photodetectors

C1 - Journal Articles Referee

Batch-to-batch variation of polymeric photovoltaic materials: Its origin and impacts on charge carrier transport and device performances

A detailed investigation of the impact of molecular weight distribution of a photoactive polymer, poly[N-9\u2032-heptadecanyl-2,7-carbazole-alt-5,5-(4\u2032,7\u2032-di-2-thienyl-2\u2032,1\u2032,3\u2032-benzothiadiazole)] (PCDTBT), on photovoltaic device performance and carrier transport properties is reported. It is found that different batches of as-received polymers have substantial differences in their molecular weight distribution. As revealed by gel permeation chromatography (GPC), two peaks can generally be observed. One of the peaks corresponds to a high molecular weight component and the other peak corresponds to a low molecular weight component. Photovoltaic devices fabricated with a higher proportion of low molecular weight component have power conversion efficiencies (PCEs) reduced from 5.7% to 2.5%. The corresponding charge carrier mobility at the short-circuit region is also significantly reduced from 2.7 7 10-5 to 1.6 7 10-8 cm2 V-1 s-1. The carrier transport properties of the polymers at various temperatures are further analyzed by the Gaussian disorder model (GDM). All polymers have similar energetic disorders. However, they appear to have significant differences in carrier hopping distances. This result provides insight into the origin of the molecular weight effect on carrier transport in polymeric semiconducting materials. Batch-to-batch variation of the photovoltaic performance of devices based on commercial samples of the polymer poly[N-9\u2032-heptadecanyl-2,7-carbazole-alt-5,5- (4\u2032,7\u2032-di-2-thienyl-2\u2032,1\u2032,3\u2032-benzothiadiazole)] (PCDTBT) is reported, with efficiency ranging from 5.7% to 2.5%. As revealed by gel permeation chromatography, bimodal distributions are observed in the molecular weight. Charge transport data suggest that low molecular weight components increase the average hopping distance, resulting in lower mobility and poorer photovoltaic performance. \ua9 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Peer reviewed: YesNRC publication: Ye

Highly Efficient Organic Light-Emitting Diode Using A Low Refractive Index Electron Transport Layer

A low refractive index electron transport layer (ETL) can be very effective in enhancing the out-coupling efficiency of an organic light-emitting diode (OLED). However, most organic films show a refractive index close to 1.8. In this work, it has been discovered that tris-[3-(3-pyridyl) mesityl] borane (3TPYMB) has a low refractive index of 1.65 (at 550 nm), which is the lowest refractive index ETL among the commonly used ETLs up to date. Using 3TPYMB as an ETL, a solution processed OLED is demonstrated with nearly a 76% enhancement in external quantum efficiency (EQE). Optical simulation results of this study show that 59% of the enhancement comes from the low refractive index 3TPYMB, and the remaining 17% from the change in charge balance due to the 3TPYMB ETL in the OLED devices