Henning Sirringhaus

Bio: Henning Sirringhaus is an academic researcher from University of Cambridge. The author has contributed to research in topics: Organic semiconductor & Field-effect transistor. The author has an hindex of 96, co-authored 467 publications receiving 50846 citations. Previous affiliations of Henning Sirringhaus include Epson & Northwestern University.

Two-dimensional charge transport in self-organized, high-mobility conjugated polymers

Abstract: Self-organization in many solution-processed, semiconducting conjugated polymers results in complex microstructures, in which ordered microcrystalline domains are embedded in an amorphous matrix1. This has important consequences for electrical properties of these materials: charge transport is usually limited by the most difficult hopping processes and is therefore dominated by the disordered matrix, resulting in low charge-carrier mobilities2 (⩽10-5 cm2 V-1 s-1). Here we use thin-film, field-effect transistor structures to probe the transport properties of the ordered microcrystalline domains in the conjugated polymer poly(3-hexylthiophene), P3HT. Self-organization in P3HT results in a lamella structure with two-dimensional conjugated sheets formed by interchain stacking. We find that, depending on processing conditions, the lamellae can adopt two different orientations—parallel and normal to the substrate—the mobilities of which differ by more than a factor of 100, and can reach values as high as 0.1 cm2 V-1 s-1 (refs 3, 4). Optical spectroscopy of the field-induced charge, combined with the mobility anisotropy, reveals the two-dimensional interchain character of the polaronic charge carriers, which exhibit lower relaxation energies than the corresponding radical cations on isolated one-dimensional chains. The possibility of achieving high mobilities via two-dimensional transport in self-organized conjugated lamellae is important for applications of polymer transistors in logic circuits5 and active-matrix displays4,6.

High-Resolution Inkjet Printing of All-Polymer Transistor Circuits

Abstract: Direct printing of functional electronic materials may provide a new route to low-cost fabrication of integrated circuits. However, to be useful it must allow continuous manufacturing of all circuit components by successive solution deposition and printing steps in the same environment. We demonstrate direct inkjet printing of complete transistor circuits, including via-hole interconnections based on solution-processed polymer conductors, insulators, and self-organizing semiconductors. We show that the use of substrate surface energy patterning to direct the flow of water-based conducting polymer inkjet droplets enables high-resolution definition of practical channel lengths of 5 micrometers. High mobilities of 0.02 square centimeters per volt second and on-off current switching ratios of 10 5 were achieved.

Integrated Optoelectronic Devices Based on Conjugated Polymers

Abstract: An all-polymer semiconductor integrated device is demonstrated with a high-mobility conjugated polymer field-effect transistor (FET) driving a polymer light-emitting diode (LED) of similar size. The FET uses regioregular poly(hexylthiophene). Its performance approaches that of inorganic amorphous silicon FETs, with field-effect mobilities of 0.05 to 0.1 square centimeters per volt second and ON-OFF current ratios of >10 6 . The high mobility is attributed to the formation of extended polaron states as a result of local self-organization, in contrast to the variable-range hopping of self-localized polarons found in more disordered polymers. The FET-LED device represents a step toward all-polymer optoelectronic integrated circuits such as active-matrix polymer LED displays.

General observation of n-type field-effect behaviour in organic semiconductors

Abstract: Organic semiconductors have been the subject of active research for over a decade now, with applications emerging in light-emitting displays and printable electronic circuits. One characteristic feature of these materials is the strong trapping of electrons but not holes1: organic field-effect transistors (FETs) typically show p-type, but not n-type, conduction even with the appropriate low-work-function electrodes, except for a few special high-electron-affinity2,3,4 or low-bandgap5 organic semiconductors. Here we demonstrate that the use of an appropriate hydroxyl-free gate dielectric—such as a divinyltetramethylsiloxane-bis(benzocyclobutene) derivative (BCB; ref. 6)—can yield n-channel FET conduction in most conjugated polymers. The FET electron mobilities thus obtained reveal that electrons are considerably more mobile in these materials than previously thought. Electron mobilities of the order of 10-3 to 10-2 cm2 V-1 s-1 have been measured in a number of polyfluorene copolymers and in a dialkyl-substituted poly(p-phenylenevinylene), all in the unaligned state. We further show that the reason why n-type behaviour has previously been so elusive is the trapping of electrons at the semiconductor–dielectric interface by hydroxyl groups, present in the form of silanols in the case of the commonly used SiO2 dielectric. These findings should therefore open up new opportunities for organic complementary metal-oxide semiconductor (CMOS) circuits, in which both p-type and n-type behaviours are harnessed.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Conjugated polymer-based organic solar cells

Abstract: The need to develop inexpensive renewable energy sources stimulates scientific research for efficient, low-cost photovoltaic devices.1 The organic, polymer-based photovoltaic elements have introduced at least the potential of obtaining cheap and easy methods to produce energy from light.2 The possibility of chemically manipulating the material properties of polymers (plastics) combined with a variety of easy and cheap processing techniques has made polymer-based materials present in almost every aspect of modern society.3 Organic semiconductors have several advantages: (a) lowcost synthesis, and (b) easy manufacture of thin film devices by vacuum evaporation/sublimation or solution cast or printing technologies. Furthermore, organic semiconductor thin films may show high absorption coefficients4 exceeding 105 cm-1, which makes them good chromophores for optoelectronic applications. The electronic band gap of organic semiconductors can be engineered by chemical synthesis for simple color changing of light emitting diodes (LEDs).5 Charge carrier mobilities as high as 10 cm2/V‚s6 made them competitive with amorphous silicon.7 This review is organized as follows. In the first part, we will give a general introduction to the materials, production techniques, working principles, critical parameters, and stability of the organic solar cells. In the second part, we will focus on conjugated polymer/fullerene bulk heterojunction solar cells, mainly on polyphenylenevinylene (PPV) derivatives/(1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C61) (PCBM) fullerene derivatives and poly(3-hexylthiophene) (P3HT)/PCBM systems. In the third part, we will discuss the alternative approaches such as polymer/polymer solar cells and organic/inorganic hybrid solar cells. In the fourth part, we will suggest possible routes for further improvements and finish with some conclusions. The different papers mentioned in the text have been chosen for didactical purposes and cannot reflect the chronology of the research field nor have a claim of completeness. The further interested reader is referred to the vast amount of quality papers published in this field during the past decade.

Long-Range Balanced Electron- and Hole-Transport Lengths in Organic-Inorganic CH3NH3PbI3

Abstract: Low-temperature solution-processed photovoltaics suffer from low efficiencies because of poor exciton or electron-hole diffusion lengths (typically about 10 nanometers). Recent reports of highly efficient CH3NH3PbI3-based solar cells in a broad range of configurations raise a compelling case for understanding the fundamental photophysical mechanisms in these materials. By applying femtosecond transient optical spectroscopy to bilayers that interface this perovskite with either selective-electron or selective-hole extraction materials, we have uncovered concrete evidence of balanced long-range electron-hole diffusion lengths of at least 100 nanometers in solution-processed CH3NH3PbI3. The high photoconversion efficiencies of these systems stem from the comparable optical absorption length and charge-carrier diffusion lengths, transcending the traditional constraints of solution-processed semiconductors.

Electroluminescence in conjugated polymers

Abstract: Research in the use of organic polymers as the active semiconductors in light-emitting diodes has advanced rapidly, and prototype devices now meet realistic specifications for applications. These achievements have provided insight into many aspects of the background science, from design and synthesis of materials, through materials fabrication issues, to the semiconductor physics of these polymers.

High-efficiency solution processable polymer photovoltaic cells by self-organization of polymer blends

Abstract: Converting solar energy into electricity provides a much-needed solution to the energy crisis the world is facing today. Polymer solar cells have shown potential to harness solar energy in a cost-effective way. Significant efforts are underway to improve their efficiency to the level of practical applications. Here, we report highly efficient polymer solar cells based on a bulk heterojunction of polymer poly(3-hexylthiophene) and methanofullerene. Controlling the active layer growth rate results in an increased hole mobility and balanced charge transport. Together with increased absorption in the active layer, this results in much-improved device performance, particularly in external quantum efficiency. The power-conversion efficiency of 4.4% achieved here is the highest published so far for polymer-based solar cells. The solution process involved ensures that the fabrication cost remains low and the processing is simple. The high efficiency achieved in this work brings these devices one step closer to commercialization.