Rene Janssen

Rene Janssen
Eindhoven University of Technology | TUE · Departments of Chemical Engineering & Chemistry and Applied Physics

Professor

About

690
Publications
94,576
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53,858
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Introduction
Our research of focuses on organic and inorganic semiconductor materials for novel opto-electronic. Synthetic chemistry is combined with time-resolved optical spectroscopy, electrochemistry, morphological characterization, and fabrication and characterization of prototype devices. In recent years activities concentrate on organic and perovskite solar cells, photodetectors, flow batteries, and solar fuels.

Publications

Publications (690)
Article
The performance of thin-film photovoltaic cells is closely related to the energy alignment of the absorber layers and charge collection layers used for constructing the device and is further influenced by the presence of energetic disorder and defects in the photoactive material. This especially holds for novel organic and perovskite semiconductors...
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Full-text available
An efficient substrate-configuration p-i-n metal-halide perovskite solar cell (PSC) is fabricated on a polymer-coated steel substrate. The optimized cell employs a Ti bottom electrode coated with a thin indium tin oxide (ITO) interlayer covered with a self-assembled [2-(9H-carbazol-9-yl)ethyl]phosphonic acid monolayer as a hole-selective contact. A...
Preprint
Touchless technology based on user interaction modes such as voice or gestures is paving the way for tomorrow’s digital ecosystems, accelerated by hygiene requirements resulting from the COVID-19 pandemic. Gesture-based touchless user interfaces typically use near-infrared (NIR) cameras. The applicability of these systems is hampered by their limit...
Article
The photoluminescence spectrum of metal‐halide perovskite films is altered by extrinsic effects, making what is measured different from what is intrinsically emitted. In article number 2102557, Tom P. A. van der Pol and co‐workers identify self‐absorption and interference to underly significant spectral distortions. They develop an optical modellin...
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Interface layers used for electron transport (ETL) and hole transport (HTL) often significantly enhance the performance of organic solar cells (OSCs). Surprisingly, interface engineering for hole extraction has received little attention thus far. By finetuning the chemical structure of carbazole-based self-assembled monolayers with phosphonic acid...
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Perovskite-based multijunction solar cells are a potentially cost-effective technology that can help surpass the efficiency limits of single-junction devices. However, both mixed-halide wide-bandgap perovskites and lead-tin narrow-bandgap perovskites suffer from non-radiative recombination due to the formation of bulk traps and interfacial recombin...
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All‐Perovskite Tandem Photovoltaics Monolithic multijunction solar cells using lead‐halide perovskite materials can deliver high performance at low material and processing costs. In article number 2110053, René A. J. Janssen and co‐workers report surface‐treatment and light‐management strategies to reduce performance losses arising from nonradiativ...
Article
Photoluminescence spectroscopy is a simple and powerful characterization technique to determine material properties and dynamic effects in metal–halide perovskite optoelectronic systems. However, self‐absorption and thin film cavity effects, amplified due to their high refractive indices, can have a significant impact on spectral lineshapes, affect...
Article
Efficient organic solar cells based on a blend of PBDS-T as a donor polymer and BTP-eC9 as non-fullerene acceptor are presented and characterized. PBDS-T is an alternating copolymer that comprises easily accessible electron-rich trialkylsilyl-substituted benzodithiophene and electron-deficient benzodithiophene-4,8-dione units and that can be effici...
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Defects in perovskite solar cells are known to affect the performance, but their precise nature, location, and role remain to be firmly established. Here, we present highly sensitive measurements of the sub-bandgap photocurrent to investigate defect states in perovskite solar cells. At least two defect states can be identified in p-i-n perovskite s...
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Since their introduction in 2017, the efficiency of lead-free halide perovskite solar cells based on Cs2AgBiBr6 has not exceeded 3%. The limiting bottlenecks are attributed to a low electron diffusion length, self-trapping events and poor selectivity of the contacts, leading to large non-radiative VOC losses. Here, 2D/3D hybrid double perovskites a...
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Fabricating efficient perovskite solar cells on steel substrates could enable easy building integration of this photovoltaic technology. Herein, an n–i–p perovskite solar cell is developed on steel substrates for top illumination. The optimized stack uses a Ti bottom electrode, covered with an indium tin oxide (ITO) interlayer and a SnO2 electron t...
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Poly(3-hexylthiophene) thin films containing carbon-based nanostructures, i.e. fullerenes such as Buckminsterfullerene (C60) or phenyl-C61-butyric acid methyl ester (PCBM), or single-walled carbon nanotubes, were investigated as heterogeneous photosensitizers producing singlet oxygen...
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Metal halide perovskite photodiodes (PPDs) offer high responsivity and broad spectral sensitivity, making them attractive for low-cost visible and near-infrared sensing. A significant challenge in achieving high detectivity in PPDs is lowering the dark current density ( J D ) and noise current ( i n ). This is commonly accomplished using charge-blo...
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Following the 1st release of the “Emerging photovoltaic (PV) reports”, the best achievements in the performance of emerging photovoltaic devices in diverse emerging photovoltaic research subjects are summarized, as reported in peer-reviewed articles in academic journals since August 2020. Updated graphs, tables, and analyses are provided with sever...
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Solution-processed photodetectors could be of use in large-area light-sensing applications because they can be fabricated at low cost on plastic substrates and their absorption spectra can be tuned by chemical design. However, fabricating photodetectors with low dark currents and integrating them into high-resolution backplanes remains challenging....
Article
Quasi-2D Perovskites The interaction between the co-solvents and the perovskite precursors dictates which quasi-2D perovskite phases are formed during spin coating or thermal annealing. In the cover artwork representing article number 2102144 by René A. J. Janssen and co-workers, methylammonium iodide is depicted in a bubble while interacting with...
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Solution‐processed quasi‐2D perovskites are promising for stable and efficient solar cells because of their superior environmental stability compared to 3D perovskites and tunable optoelectronic properties. Changing the number of inorganic layers (n) sandwiched between the organic spacers allows for tuning of the bandgap. However, narrowing the pha...
Preprint
Following the 1 release of the “Emerging PV reports” , the best achievements in the performance of emerging photovoltaic devices in diverse emerging photovoltaic research subjects are summarized, as reported in peer-reviewed articles in academic journals since August 2020. Updated graphs, tables and analyses are provided with several performance pa...
Preprint
Following the 1 release of the “Emerging PV reports” , the best achievements in the performance of emerging photovoltaic devices in diverse emerging photovoltaic research subjects are summarized, as reported in peer-reviewed articles in academic journals since August 2020. Updated graphs, tables and analyses are provided with several performance pa...
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Full-text available
Recent developments toward high-energy-density all-organic redox flow batteries suggest the advantageous use of molecules exhibiting multielectron redox events. Following this approach, organic anolytes are developed that feature multiple consecutive one-electron reductions. These anolytes are based on N-methylphthalimide, which exhibits a single r...
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Lead–tin (Pb–Sn) hybrid perovskite materials possess ideal narrow bandgaps (1.2–1.4 eV) for efficient single-junction and tandem solar cells. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is commonly used as hole transport layer (HTL) for Pb–Sn perovskite solar cells (PSCs), despite its poor stability with these perovskites. He...
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Light-induced halide segregation hampers obtaining stable wide-band-gap solar cells based on mixed iodide–bromide perovskites. So far, the effect of prolonged illumination on the performance of mixed-halide perovskite solar cells has not been studied in detail. It is often assumed that halide segregation leads to a loss of open-circuit voltage. By...
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Cs2AgBiBr6 has attracted much interest as a potential lead-free alternative for perovskite solar cells. Although this material offers encouraging optoelectronic features, severe bottlenecks limit the performance of the resulting solar cells to a power conversion efficiency of below 3%. Here, the performance-limiting factors of this material are inv...
Article
In recent years, noncovalently assembled monolayers of conjugated, semiconducting polymers with thickness less than 5 nm have attracted increasing attention because of their determining role in charge carrier transport in field-effect transistors and their multifunctionality in other electronic devices. This article reviews recent advances in vario...
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Electron transport layers (ETLs) placed between the electrodes and a photoactive layer can enhance the performance of organic solar cells but also impose limitations. Most ETLs are ultrathin films, and their deposition can disturb the morphology of the photoactive layers, complicate device fabrication, raise cost, and also affect device stability....
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Side-chain engineering is an important strategy in designing novel polymer semiconductor materials for high-efficient organic solar cells. The use of trialkylsilyl side chains can improve the photovoltaic efficiency by decreasing the energy of the HOMO of the polymer and improving its crystallinity and hole mobility. Compared to simple linear deriv...
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Parasitic optical absorption is one of the root causes of the moderate efficiency of metal halide perovskite solar cells (PSCs) with an opaque substrate configuration. Here, we investigate the reduction of these optical losses by using thin (7–10 nm), undoped, thermally evaporated 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluoren...
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The combination of narrow-bandgap diketopyrrolopyrrole (DPP) polymers and nonfullerene acceptors (NFAs) seems well-matched for solar cells that exclusively absorb in the near infrared but they rarely provide high efficiency. One reason is that processing of the active layer is complicated by the fact that DPP-based polymers are generally only suffi...
Preprint
Emerging photovoltaics (PVs), focuses on a variety of applications complementing large scale electricity generation. For instance, organic, dye-sensitized and some perovskite solar cells are considered in building integration, greenhouses, wearable and indoors, thereby motivating research on flexible, transparent, semitransparent, and multi-junctio...
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The incorporation of additives to modulate the properties of metal halide perovskite thin films has become a successful approach in improving the power conversion efficiency of perovskite‐based solar cells. Herein, the beneficial use of sodium diethyldithiocarbamate (NaDEDTC) as processing agent in improving the open‐circuit voltage of methylammoni...
Preprint
Emerging photovoltaics (PVs), focuses on a variety of applications complementing large scale electricity generation. For instance, organic, dye-sensitized and some perovskite solar cells are considered in building integration, greenhouses, wearable and indoors, thereby motivating research on flexible, transparent, semitransparent, and multi-junctio...
Article
Full-text available
Emerging photovoltaics (PVs) focus on a variety of applications complementing large scale electricity generation. Organic, dye‐sensitized, and some perovskite solar cells are considered in building integration, greenhouses, wearable, and indoor applications, thereby motivating research on flexible, transparent, semitransparent, and multi‐junction P...
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Full-text available
The effect of the nature of the π-conjugated linker that is positioned between electron-deficient 2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (DPP) and electron-rich dithieno[3,2-b:2′,3′-d]pyrrole (DTP) units in alternating DPP–DTP copolymers on the optical and electrochemical band gaps and the effective exciton binding energy is investigated for si...
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The optical properties of two sets of donor–acceptor–donor molecules with terminal bithiophene donor units and a central diketopyrrolopyrrole (DPP) acceptor unit are studied. The two sets differ in the alkyl chains on the DPP, which are either branched at the α-carbon (3-pentyl) (1–4) or linear (n-hexyl) (5–8). Within each set, the molecules differ...
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Few semiconducting polymers are known that possess more than one semi-crystalline structure. Guidelines for rationalizing or creating polymorphism in these materials do not exist. Two different semi-crystalline polymorphs, β 1 and β 2 , and an amorphous α phase have recently been identified for alternating diketopyrrolopyrrole-quaterthiophene copol...
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Perovskite semiconductors hold a unique promise in developing multijunction solar cells with high-efficiency and low-cost. Besides design constraints to reduce optical and electrical losses, integrating several very different perovskite absorber layers in a multijunction cell imposes a great processing challenge. Here, we report a versatile two-ste...
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In developing organic semiconductor polymers for photovoltaic applications, chlorine substitution has become an effective strategy in replacing fluorine substitution to overcome the drawbacks of low yield and high cost, commonly associated with fluorination. In general, several molecular positions are available for chlorination. To obtain a clear u...
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Two asymmetric thiophene (T)/pyridine (Py) flanked diketopyrrolopyrrole (DPP) polymers with a regiorandom and regioregular conjugated backbone are synthesized via a Stille polycondensation to investigate the effect of regioregularity on their optoelectronic properties and photovoltaic performance in fullerene-based polymer solar cells. Surprisingly...
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To date, substrate‐configuration metal‐halide perovskite solar cells (PSCs) fabricated on opaque substrates such as metal foils provide inferior efficiencies compared with superstrate‐configuration cells on transparent substrates such as glass. Herein, a substrate‐configuration PSC on planarized steel is presented. To quantify the differences betwe...
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Photovoltaic devices that switch color depending on illumination conditions may find application in future smart window applications. Here a photochromic diarylethene molecule is used as sensitizer in a ternary bulk heterojunction blend, employing poly(4-butylphenyldiphenylamine) (poly-TPD) and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) fo...
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Compared to conjugated polymers, small‐molecule organic semiconductors present negligible batch‐to‐batch variations, but presently provide comparatively low power conversion efficiencies (PCEs) in small‐molecular organic solar cells (SM‐OSCs), mainly due to suboptimal nanomorphology. Achieving precise control of the nanomorphology remains challengi...
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Diketopyrrolopyrrole (DPP) polymers possess narrow optical bandgaps and high charge carrier mobilities which make them attractive for solar cell applications. DPP polymers are generally only soluble in chlorinated solvents, which is a drawback for commercial application. Solubility in non-halogenated solvents can be achieved by reducing the transla...
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Introducing solubilizing α‐branched alkyl chains on a poly(diketopyrrolopyrrole‐ alt ‐terthiophene) results in a dramatic change of the structural, optical, and electronic properties compared to the isomeric polymer carrying β‐branched alkyl side chains. When branched at the α‐position the alkyl substituent creates a steric hindrance that reduces t...
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Organic photodetectors (OPDs) have gained increasing interest as they offer cost‐effective fabrication methods using low temperature processes, making them particularly attractive for large area image detectors on lightweight flexible plastic substrates. Moreover, their photophysical and optoelectronic properties can be tuned both at a material and...
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Organic electrochemical transistors (OECTs) show great promise for flexible, low‐cost, and low‐voltage sensors for aqueous solutions. The majority of OECT devices are made using the polymer blend poly(ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), in which PEDOT is intrinsically doped due to inclusion of PSS. Because of this intrinsic...
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In article number 2000270, Alberto Salleo, Yoeri van de Burgt, and co‐workers add small‐molecule amines to PEDOT:PSS in solution to fabricate high‐performance enhancement‐mode organic electrochemical transistors. Small‐molecule amines efficiently de‐dope PEDOT:PSS, shifting the transistor operation from depletion to enhancement mode without degradi...
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Storing solar energy in chemical bonds is an effective strategy to overcome the intermittency of sunlight as an energy source. Here, we demonstrate unassisted light-driven electrochemical aqueous carbon dioxide reduction to carbon monoxide and methane using p-i-n double-cation lead halide perovskite solar cells in combination with catalytic electro...
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Developing efficient narrow bandgap Pb–Sn hybrid perovskite solar cells with high Sn‐content is crucial for perovskite‐based tandem devices. Film properties such as crystallinity, morphology, surface roughness, and homogeneity dictate photovoltaic performance. However, compared to Pb‐based analogs, controlling the formation of Sn‐containing perovsk...