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Orlando, FL, United States

Han C.,Henan University | Cheng Y.,Henan University | Chen L.,Henan University | Qian L.,Henan University | And 5 more authors.
ACS Applied Materials and Interfaces | Year: 2016

A highly efficient inverted polymer solar cell (PSC) has been successfully demonstrated by using a ZnO nanoparticle (NP) and poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctyfluorene)] (PFN) bilayer structure as an effective electron collecting layer. This ZnO/PFN bilayer structure is designed to combine the advantages of both ZnO and PFN, based on the performance comparison of ZnO-only, PFN-only, and ZnO/PFN bilayer devices in our work. ZnO NPs can serve as an efficient electron transport and buffer layer for reduced series resistance, while the PFN interlayer can improve the energy level alignment of devices through the formation of an interfacial dipole. With the enhanced electron extraction induced by the ZnO/PFN bilayer structure and PTB7:ICBA:PC71BM ternary system, the corresponding inverted PSC device shows a high PCE of 9.3%, which is more than a 15% improvement compared to the ZnO- or PFN-only devices. © 2016 American Chemical Society. Source


Grant
Agency: National Science Foundation | Branch: | Program: SBIR | Phase: Phase II | Award Amount: 683.35K | Year: 2014

This Small Business Innovation Research (SBIR) Phase II project aims to further enhance the efficiency and lifetime of quantum dot light emitting diodes (QD-LEDs) used for displays. An active matrix QD-LED prototype display will be demonstrated using solution processing. The lifetime of QD-LED will be extended by determining degradation mechanisms, and development of new materials, modified device processing and encapsulation techniques. The effects of charge imbalance and light trapping on the efficiency of QD-LED will be determined and optimized. External quantum efficiencies will exceed 18%. Lifetimes of QD-LEDs exceeding 10,000 hours for all three primary colors will be demonstrated, which meets the requirement for mobile display applications. The broader impact/commercial potential of this project will be a demonstration that quantum dot light-emitting diodes (QD-LEDs) have the commercial advantages of high efficiencies and long lifetimes. QD-LED will be welcomed by the display industry which is now desperately searching for next generation technologies. The demonstration of an active matrix QD-LED display prototype with a solution printing process will be a critical step towards the commercialization. The systematic investigation of technical details involved in the printing process of active matrix QD-LEDs will enable the construction of a pilot facility and eventual mass production. The simple architecture and solution fabrication process will provide significant cost advantages over conventional processes.


Grant
Agency: NSF | Branch: Standard Grant | Program: | Phase: | Award Amount: 180.00K | Year: 2013

This Small Business Innovation Research Phase I project seeks to demonstrate ultra high efficiency quantum dot light-emitting diodes (QD-LEDs) using a top-emitting structure and micro-lens array for display applications. Two key challenges will be addressed. First, a novel top-emitting structure will be explored based on the previous efficient bottom-emitting QD-LEDs. Use of top-emitting structure removes light trapped through the wave-guide mode within the glass substrate, which improves light out-coupling. A micro-lens array will be applied on top of the QD-LEDs to further enhance the light extraction. The project will focus on a number of innovative approaches. Micro-lens arrays will be fabricated using a novel stamp printing method. A small size micro-lens along with a top-emitting structure will minimize the pixel blurring effect induced by the conventional out-coupling micro-lens. Secondly, high refractive index material will be used to fabricate a micro-lens to match the refractive index of the transparent electrode, hence improving light extraction efficiency.

The broader impact/commercial potential of this project lies is to enable the commercialization of QD-LED displays, solid-state lighting and other applications. QD-LEDs provide intrinsically higher color purity compared to LCD or organic light-emitting diode (OLED) technology and are suitable for display applications. However, current QD-LED solutions suffer from lower efficiency compared to LCD and OLED. The company?s innovative nanomaterials and device architecture has enabled very efficient bottom-emitting QD-LEDs with high external quantum efficiency. Additionally, the multi-layer structure in the company?s QD-LED are deposited through solution processing, which reduces the cost significantly. It is expected that a better performing and substantially less expensive QD-LED will quickly gain considerable market share in a $60B market that ships over 1.5B units a year.


Grant
Agency: NSF | Branch: Standard Grant | Program: | Phase: SMALL BUSINESS PHASE II | Award Amount: 1.27M | Year: 2014

This Small Business Innovation Research (SBIR) Phase II project aims to further enhance the efficiency and lifetime of quantum dot light emitting diodes (QD-LEDs) used for displays. An active matrix QD-LED prototype display will be demonstrated using solution processing. The lifetime of QD-LED will be extended by determining degradation mechanisms, and development of new materials, modified device processing and encapsulation techniques. The effects of charge imbalance and light trapping on the efficiency of QD-LED will be determined and optimized. External quantum efficiencies will exceed 18%. Lifetimes of QD-LEDs exceeding 10,000 hours for all three primary colors will be demonstrated, which meets the requirement for mobile display applications.

The broader impact/commercial potential of this project will be a demonstration that quantum dot light-emitting diodes (QD-LEDs) have the commercial advantages of high efficiencies and long lifetimes. QD-LED will be welcomed by the display industry which is now desperately searching for next generation technologies. The demonstration of an active matrix QD-LED display prototype with a solution printing process will be a critical step towards the commercialization. The systematic investigation of technical details involved in the printing process of active matrix QD-LEDs will enable the construction of a pilot facility and eventual mass production. The simple architecture and solution fabrication process will provide significant cost advantages over conventional processes.


Shen H.,Henan University | Zheng Y.,NanoPhotonica | Wang H.,Henan University | Xu W.,Henan University | And 5 more authors.
Nanotechnology | Year: 2013

In this paper, we present an innovative method for the synthesis of CdTe/CdSe type-II core/shell structure quantum dots (QDs) using 'greener' chemicals. The PL of CdTe/CdSe type-II core/shell structure QDs ranges from 600 to 820 nm, and the as-synthesized core/shell structures show narrow size distributions and stable and high quantum yields (50-75%). Highly efficient near-infrared light-emitting diodes (LEDs) have been demonstrated by employing the CdTe/CdSe type-II core/shell QDs as emitters. The devices fabricated based on these type-II core/shell QDs show color-saturated near-infrared emission from the QD layers, a low turn-on voltage of 1.55 V, an external quantum efficiency (EQE) of 1.59%, and a current density and maximum radiant emittance of 2.1 × 103 mA cm-2 and 17.7 mW cm-2 at 8 V; it is the first report to use type-II core/shell QDs as near-infrared emitters and these results may offer a practicable platform for the realization of near-infrared QD-based light-emitting diodes, night-vision-readable displays, and friend/foe identification system. © 2013 IOP Publishing Ltd. Source

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