Online citations, reference lists, and bibliographies.
← Back to Search

Light‐Stimulated Charge Transport In Bilayer Molecular Junctions For Photodetection

S. K. Saxena, S. R. Smith, Mustafa Supur, R. McCreery
Published 2019 · Materials Science

Cite This
Download PDF
Analyze on Scholarcy
DOI: 10.1002/adom.201901053 been studied extensively.[1,3] The field is driven in part by the possibility of new electronic functions in molecular devices and the wide variety of molecular structures available, presumably with a broad range of electronic behaviors.[4] “Large area” or “ensemble” MJs with partially transparent contacts enable the use of optical spectroscopy for characterization and monitoring of molecular electronic devices using infrared absorption,[5] Raman,[6] and UV-vis spectroscopy.[4d,7] While optical spectroscopy is normally a probe of device structure during fabrication and operation, the field of “molecular optoelectronics” investigates stimulation of transport with light or generation of light in response to an external bias.[8] Photocurrent (PC) generation and changes in MJ conductance by incident light have been reported for single molecules and molecular ensembles and examined theoretically.[4a,9] We have reported PCs and photoconductance changes in carbon-based MJs, mediated by internal photoemission (IPE)[10] and optical absorption in the molecular layer.[11] The observed PC tracks the in situ UV-vis absorption spectrum of the molecular layer when the transport distance exceeds 5 nm, and the PC polarity (i.e., the charge transport direction) and induced photovoltage correlate strongly with which orbitals mediate transport (highest occupied molecular orbital (HOMO) or lowest unoccupied molecular orbital (LUMO)).[11b] Carbon-based MJs also exhibit photoemission from hot electrons,[8c,12] and transport in thiol-based large-area MJs can couple to plasmons in the contacts to emit light.[8d,13] For PCs in unbiased, Au/carbon/molecule/carbon/Au MJs with identical top and bottom electrodes, the direction of illumination did not cause a change in PC sign, indicating that there must be some inherent asymmetry in the device. We attributed the asymmetry in single-component carbon-based MJs to a difference in electronic coupling at the two electrode contacts, one of which is covalent and the other physisorbed.[11b] This effect was predicted theoretically by Galperin et al.[8b,14] Since the internal electric field generated by the effect is small (10–30 mV), the resulting PCs are also small for single-component MJs, and would likely be absent if the electronic coupling to both electrodes were identical. We recently reported a different approach in which a molecular bilayer was used to create asymmetry, leading to significantly larger PCs.[15] Successive reduction of two diazonium reagents[16] resulted in a covalent Eleven bilayer molecular junctions (MJs) consisting of two different 5–7 nm thick molecular layers between conducting contacts are investigated to determine how orbital energies and optical absorbance spectra of the oligomers affect the photocurrent (PC) response, the direction of photoinduced charge transport, and maximum response wavelength. Photometric sensitivity of 2 mA W−1 and a detection limit of 11 pW are demonstrated for MJs, yielding an internal quantum efficiency of 0.14 electrons per absorbed photon. For unbiased MJs, the PC tracks the absorption spectrum of the molecular layer, and is stable for >5 h of illumination. The organic/organic (O/O) interface between the molecular layers within bilayer MJs is the primary determinant of PC polarity, and the bilayer MJ mechanism is conceptually similar to that of a single O/O heterojunction studied in bilayers of much greater thickness. The charge transport direction of the 11 MJs is completely consistent with hole-dominated transport of photogenerated carriers. For MJs illuminated while an external bias is applied, the PC greatly exceeds the dark current by factors of 102 to 105, depending on bias, bilayer structure, and wavelength. The bilayer MJs are amenable to flexible substrates, and may have applications as sensitive, wavelength-specific photodetectors.
This paper references
Photoconductance of organic single-molecule contacts
J. Viljas (2007)
Monitoring of Energy Conservation and Losses in Molecular Junctions through Characterization of Light Emission
O. Ivashenko (2016)
In situ Structural Characterization of Metal−Molecule−Silicon Junctions Using Backside Infrared Spectroscopy
A. Scott (2008)
Current-induced light emission and light-induced current in molecular-tunneling junctions.
Michael Galperin (2005)
FTIR spectroscopy of buried interfaces in molecular junctions.
Yongseok Jun (2004)
Single-molecule junctions beyond electronic transport.
Swaroop Aradhya (2013)
Molecular rectifiers: a new design based on asymmetric anchoring moieties.
C. Van Dyck (2015)
Formation of silicon-based molecular electronic structures using flip-chip lamination.
M. Coll (2009)
Hybrid Graphene Ribbon/Carbon Electrodes for High‐Performance Energy Storage
Anna K Farquhar (2018)
Light Emission as a Probe of Energy Losses in Molecular Junctions.
O. Ivashenko (2016)
From active plasmonic devices to plasmonic molecular electronics
J. Lacroix (2019)
441, 69; b)
H B Akkerman (2006)
Analytical chemistry in molecular electronics.
A. Bergren (2011)
Organic light detectors: photodiodes and phototransistors.
Kang-Jun Baeg (2013)
Afanasév, Internal Photoemission Spectroscopy: Principles and Applications
V V. (2008)
Towards High Performance Organic Photovoltaic Cells: A Review of Recent Development in Organic Photovoltaics
Junsheng Yu (2014)
Internal photoemission in molecular junctions: parameters for interfacial barrier determinations.
Jerry A Fereiro (2015)
Chapter 4 – Internal Photoemission Spectroscopy Methods
V. Afanas’ev (2008)
Large-Area, Ensemble Molecular Electronics: Motivation and Challenges.
A. Vilan (2017)
Control of Electronic Symmetry and Rectification through Energy Level Variations in Bilayer Molecular Junctions.
A. Bayat (2016)
Towards molecular electronics with large-area molecular junctions
H. Akkerman (2006)
Photonics and spectroscopy in nanojunctions: a theoretical insight.
Michael Galperin (2017)
137, 1296; b)
J A Fereiro (2013)
Characterization of Growth Patterns of Nanoscale Organic Films on Carbon Electrodes by Surface Enhanced Raman Spectroscopy.
Mustafa Supur (2017)
Molecular diodes with rectification ratios exceeding 105 driven by electrostatic interactions.
X. Chen (2017)
A critical perspective on molecular electronic junctions: there is plenty of room in the middle.
R. McCreery (2013)
Light-induced current in molecular tunneling junctions excited with intense shaped pulses
B. Fainberg (2007)
Orbital Control of Photocurrents in Large Area All-Carbon Molecular Junctions.
Amin Morteza Najarian (2018)
What is the Barrier for Tunneling Through Alkyl Monolayers? Results from n‐ and p‐Si–Alkyl/Hg Junctions
A. Salomon (2007)
Electron Energetics at Surfaces and Interfaces: Concepts and Experiments†
D. Cahen (2003)
In-Situ Optical Absorbance Spectroscopy of Molecular Layers in Carbon Based Molecular Electronic Devices
Andrew P. Bonifas (2008)
The Molecular Photo-Cell: Quantum Transport and Energy Conversion at Strong Non-Equilibrium
S. Ajisaka (2015)
Derivatization of optically transparent materials with diazonium reagents for spectroscopy of buried interfaces.
A. Mahmoud (2009)
Internal Photoemission Spectroscopy: Principles and Applications
V. V. Afanasʹev (2008)
Observation of multiple vibrational modes in ultrahigh vacuum tip-enhanced Raman spectroscopy combined with molecular-resolution scanning tunneling microscopy.
N Jiang (2012)
Revealing the molecular structure of single-molecule junctions in different conductance states by fishing-mode tip-enhanced Raman spectroscopy
Z. Liu (2011)
Activationless charge transport across 4.5 to 22 nm in molecular electronic junctions
Haijun Yan (2013)
Molecular electronic plasmonics
Tao Wang (2016)
Optical modulation of nano-gap tunnelling junctions comprising self-assembled monolayers of hemicyanine dyes
P. Pourhossein (2016)
Towards Integrated Molecular Electronic Devices: Characterization of Molecular Layer Integrity During Fabrication Processes
A. Mahmoud (2011)
20, 4910; c)
D H Wang (2010)
Solution-processable polymer based photovoltaic devices with concentration graded bilayers made via composition control of a poly(3-hexylthiophene)/[6,6]-phenyl C61-butyric acidmethyl ester
D. H. Wang (2010)
Molecular optoelectronics: the interaction of molecular conduction junctions with light.
Michael Galperin (2012)
Energetics of molecular interfaces
D. Cahen (2005)
77, 155119; d)
P Pourhossein
Modeling elastic and photoassisted transport in organic molecular wires: Length dependence and current-voltage characteristics
J. Viljas (2008)
89, 6463; d)
M Supur (2004)
Covalently bonded single-molecule junctions with stable and reversible photoswitched conductivity
Chuancheng Jia (2016)
In situ Raman spectroscopy of bias-induced structural changes in nitroazobenzene molecular electronic junctions.
Aletha M. Nowak (2004)
Enabling Multifunctional Organic Transistors with Fine-Tuned Charge Transport.
C. Di (2019)
High-Yield Functional Molecular Electronic Devices.
Hyunhak Jeong (2017)
Robust All-Carbon Molecular Junctions on Flexible or Semi-Transparent Substrates Using "Process-Friendly" Fabrication.
Amin Morteza Najarian (2016)
Photoemission of Holes and Electrons from Aluminum into Aluminum Oxide
A. Goodman (1970)
Electrically-Excited Surface Plasmon Polaritons with Directionality Control
Zhaogang Dong (2015)
Direct optical determination of interfacial transport barriers in molecular tunnel junctions.
Jerry A Fereiro (2013)
On-chip molecular electronic plasmon sources based on self-assembled monolayer tunnel junctions
Wei Du (2016)
Structure Controlled Long-Range Sequential Tunneling in Carbon-Based Molecular Junctions.
Amin Morteza Najarian (2017)
Nanometric building blocks for robust multifunctional molecular junctions.
D. D. James (2018)
Fermi Level Pinning and Orbital Polarization Effects in Molecular Junctions: The Role of Metal Induced Gap States
C. Dyck (2014)
Tailored Surfaces/Assemblies for Molecular Plasmonics and Plasmonic Molecular Electronics.
J. Lacroix (2017)
Long-Range Activationless Photostimulated Charge Transport in Symmetric Molecular Junctions.
Amin Morteza Najarian (2019)
Molecular-Scale Electronics: From Concept to Function.
D. Xiang (2016)
Photocurrent, Photovoltage, and Rectification in Large‐Area Bilayer Molecular Electronic Junctions
S. R. Smith (2018)
Light Management with Patterned Micro‐ and Nanostructure Arrays for Photocatalysis, Photovoltaics, and Optoelectronic and Optical Devices
W. Wang (2019)
Fermi-level pinning at conjugated polymer interfaces
C. Tengstedt (2006)
Molecular transport junctions: asymmetry in inelastic tunneling processes.
Michael Galperin (2005)
Experimental and Theoretical Analysis of Nanotransport in Oligophenylene Dithiol Junctions as a Function of Molecular Length and Contact Work Function.
Z. Xie (2015)
Molecular tunnel junctions based on π-conjugated oligoacene thiols and dithiols between Ag, Au, and Pt contacts: effect of surface linking group and metal work function.
B. Kim (2011)
Photoconductance from Exciton Binding in Molecular Junctions.
J. Zhou (2018)

This paper is referenced by
Semantic Scholar Logo Some data provided by SemanticScholar