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Zheng Xu

Other affiliations: IMEC, Solarmer Energy, Inc., Katholieke Universiteit Leuven  ...read more
Bio: Zheng Xu is an academic researcher from Hangzhou Normal University. The author has contributed to research in topics: Catalysis & Enantioselective synthesis. The author has an hindex of 52, co-authored 312 publications receiving 15446 citations. Previous affiliations of Zheng Xu include IMEC & Solarmer Energy, Inc..


Papers
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Journal ArticleDOI
TL;DR: The past success in organic light-emitting diodes provides scientists with confidence that organic photovoltaic devices will be a vital alternate to the inorganic counterpart, and the easiness of the fabrication holds the promise of very low-cost manufacturing process.
Abstract: Sun is the largest carbon-neutral energy source that has not been fully utilized. Although there are solar cell devices based on inorganic semiconductor to efficiently harvest solar energy, the cost of these conventional devices is too high to be economically viable. This is the major motivation for the development of organic photovoltaic (OPV) materials and devices, which are envisioned to exhibit advantages such as low cost, flexibility, and abundant availability. [1] The past success in organic light-emitting diodes provides scientists with confidence that organic photovoltaic devices will be a vital alternate to the inorganic counterpart. At the heart of the OPV technology advantage is the easiness of the fabrication, which holds the promise of very low-cost manufacturing process. A simple, yet successful technique is the solution-processed bulk heterojunction (BHJ) solar cell composed of electron-donating semiconducting polymers and electron-withdrawing fullerides as active layers. [2] The composite active layer can be prepared as a large area in a single step by using techniques such as spin-coating, inkjet-printing, spraycoating, gravure-coating, roller-casting etc. [3] In the last fifteen years, a significant progress has been made on the improvement of the power-conversion efficiency (PCE) of polymer BHJ solar cells, and the achieved efficiencies have evolved from less than 1% in the poly(phenylene vinylene) (PPV) system in 1995, [2] to 4‐5% in the poly(3-hexylthiphene) (P3HT) system in 2005, [4] to around 6%, as reported recently. [5] However, the efficiency of polymer solar cells is still significantly lower than their inorganic counterparts, such as silicon, CdTe and CIGS, which prevents practical applications in large scale.

3,602 citations

Journal ArticleDOI
TL;DR: This review article takes a retrospective look at the research and development of OPV, and focuses on recent advances of solution-processed materials and devices during the last decade, particular the polymer version of the materials and Devices.
Abstract: Organic photovoltaic (OPV) technology has been developed and improved from a fancy concept with less than 1% power conversion efficiency (PCE) to over 10% PCE, particularly through the efforts in the last decade. The significant progress is the result of multidisciplinary research ranging from chemistry, material science, physics, and engineering. These efforts include the design and synthesis of novel compounds, understanding and controlling the film morphology, elucidating the device mechanisms, developing new device architectures, and improving large-scale manufacture. All of these achievements catalyzed the rapid growth of the OPV technology. This review article takes a retrospective look at the research and development of OPV, and focuses on recent advances of solution-processed materials and devices during the last decade, particular the polymer version of the materials and devices. The work in this field is exciting and OPV technology is a promising candidate for future thin film solar cells.

1,073 citations

Journal ArticleDOI
TL;DR: In this paper, the role of the additive in the mixture solvent and how the optimized nanoscale phase separation develops laterally and vertically during the non-equilibrium spin-coating process was investigated.
Abstract: The mixed solvent approach has been demonstrated as a promising method to modify nanomorphology in polymer solar cells. This work aims to understand the unique role of the additive in the mixture solvent and how the optimized nanoscale phase separation develops laterally and vertically during the non-equilibrium spin-coating process. We found the donor/acceptor components in the active layer can phase separate into an optimum morphology with the additive. Supported by AFM, TEM and XPS results, we proposed a model and identified relevant parameters for the additive such as solubility and vapor pressures. Other additives are discovered to show the ability to improve polymer solar cell performance as well.

683 citations

Journal ArticleDOI
TL;DR: In this article, the vertical phase separation of spin-coated poly(3-hexylthiophene) (P3HT):fullerene derivative blends was investigated using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM).
Abstract: A method which enables the investigation of the buried interfaces without altering the properties of the polymer films is used to study vertical phase separation of spin-coated poly(3-hexylthiophene) (P3HT):fullerene derivative blends. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analysis reveals the P3HT enrichment at the free (air) surfaces and abundance of fullerene derivatives at the organic/substrate interfaces. The vertical phase separation is attributed to the surface energy difference of the components and their interactions with the substrates. This inhomogeneous distribution of the donor and acceptor components significantly affects photovoltaic device performance and makes the inverted device structure a promising choice.

676 citations


Cited by
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Journal ArticleDOI
TL;DR: Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density.
Abstract: In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density of ES (476 references).

7,642 citations

Journal ArticleDOI
TL;DR: In this paper, a polymer solar cell based on a bulk hetereojunction design with an internal quantum efficiency of over 90% across the visible spectrum (425 nm to 575 nm) is reported.
Abstract: A polymer solar-cell based on a bulk hetereojunction design with an internal quantum efficiency of over 90% across the visible spectrum (425 nm to 575 nm) is reported. The device exhibits a power-conversion efficiency of 6% under standard air-mass 1.5 global illumination tests.

4,002 citations

Journal ArticleDOI
TL;DR: In this article, a review summarizes recent progress in the development of polymer solar cells and provides a synopsis of major achievements in the field over the past few years, while potential future developments and the applications of this technology are also briefly discussed.
Abstract: This Review summarizes recent progress in the development of polymer solar cells. It covers the scientific origins and basic properties of polymer solar cell technology, material requirements and device operation mechanisms, while also providing a synopsis of major achievements in the field over the past few years. Potential future developments and the applications of this technology are also briefly discussed.

3,832 citations

Journal ArticleDOI
TL;DR: In this article, the authors showed that PFN can be incorporated into polymer light-emitting devices (PLEDs) to enhance electron injection from high-work-function metals such as aluminium (work function w of 4.3 eV) and gold (w ¼ 5.2 eV).
Abstract: typically based on n-type metal oxides, our device is solutionprocessed at room temperature, enabling easy processibility over a large area. Accordingly, the approach is fully amenable to highthroughput roll-to-roll manufacturing techniques, may be used to fabricate vacuum-deposition-free PSCs of large area, and find practical applications in future mass production. Moreover, our discovery overturns a well-accepted belief (the inferior performance of inverted PSCs) and clearly shows that the characteristics of high performance, improved stability and ease of use can be integrated into a single device, as long as the devices are optimized, both optically and electrically, by means of a meticulously designed device structure. We also anticipate that our findings will catalyse the development of new device structures and may move the efficiency of devices towards the goal of 10% for various material systems. Previously, we reported that PFN can be incorporated into polymer light-emitting devices (PLEDs) to enhance electron injection from high-work-function metals such as aluminium (work function w of 4.3 eV) 22,23 and has thus been used to realize high-efficiency, air-stable PLEDs 24 . Furthermore, we also found that efficient electron injection can be obtained even in the most noble metals with extremely high work functions, such as gold (w ¼ 5.2 eV), by lowering the effective work function (for example lowering w in gold by 1.0 eV), which has previously been ascribed to the formation of a strong interface dipole 25 .

3,651 citations

Journal ArticleDOI
TL;DR: The past success in organic light-emitting diodes provides scientists with confidence that organic photovoltaic devices will be a vital alternate to the inorganic counterpart, and the easiness of the fabrication holds the promise of very low-cost manufacturing process.
Abstract: Sun is the largest carbon-neutral energy source that has not been fully utilized. Although there are solar cell devices based on inorganic semiconductor to efficiently harvest solar energy, the cost of these conventional devices is too high to be economically viable. This is the major motivation for the development of organic photovoltaic (OPV) materials and devices, which are envisioned to exhibit advantages such as low cost, flexibility, and abundant availability. [1] The past success in organic light-emitting diodes provides scientists with confidence that organic photovoltaic devices will be a vital alternate to the inorganic counterpart. At the heart of the OPV technology advantage is the easiness of the fabrication, which holds the promise of very low-cost manufacturing process. A simple, yet successful technique is the solution-processed bulk heterojunction (BHJ) solar cell composed of electron-donating semiconducting polymers and electron-withdrawing fullerides as active layers. [2] The composite active layer can be prepared as a large area in a single step by using techniques such as spin-coating, inkjet-printing, spraycoating, gravure-coating, roller-casting etc. [3] In the last fifteen years, a significant progress has been made on the improvement of the power-conversion efficiency (PCE) of polymer BHJ solar cells, and the achieved efficiencies have evolved from less than 1% in the poly(phenylene vinylene) (PPV) system in 1995, [2] to 4‐5% in the poly(3-hexylthiphene) (P3HT) system in 2005, [4] to around 6%, as reported recently. [5] However, the efficiency of polymer solar cells is still significantly lower than their inorganic counterparts, such as silicon, CdTe and CIGS, which prevents practical applications in large scale.

3,602 citations