2 research outputs found
High-Efficiency Selective Electron Tunnelling in a Heterostructure Photovoltaic Diode
A heterostructure
photovoltaic diode
featuring an all-solid-state TiO<sub>2</sub>/graphene/dye ternary
interface with high-efficiency photogenerated charge separation/transport
is described here. Light absorption is accomplished by dye molecules
deposited on the outside surface of graphene as photoreceptors to
produce photoexcited electron–hole pairs. Unlike conventional
photovoltaic conversion, in this heterostructure both photoexcited
electrons and holes tunnel along the same direction into graphene,
but only electrons display efficient ballistic transport toward the
TiO<sub>2</sub> transport layer, thus leading to effective photon-to-electricity
conversion. On the basis of this ipsilateral selective electron tunnelling
(ISET) mechanism, a model monolayer photovoltaic device (PVD) possessing
a TiO<sub>2</sub>/graphene/acridine orange ternary interface showed
∼86.8% interfacial separation/collection efficiency, which
guaranteed an ultrahigh absorbed photon-to-current efficiency (APCE,
∼80%). Such an ISET-based PVD may become a fundamental device
architecture for photovoltaic solar cells, photoelectric detectors,
and other novel optoelectronic applications with obvious advantages,
such as high efficiency, easy fabrication, scalability, and universal
availability of cost-effective materials
Label-Free Dynamic Detection of Single-Molecule Nucleophilic-Substitution Reactions
The
mechanisms of chemical reactions, including the transformation
pathways of the electronic and geometric structures of molecules,
are crucial for comprehending the essence and developing new chemistry.
However, it is extremely difficult to realize at the single-molecule
level. Here, we report a single-molecule approach capable of electrically
probing stochastic fluctuations under equilibrium conditions and elucidating
time trajectories of single species in non-equilibrated systems. Through
molecular engineering, a single molecular wire containing a functional
center of 9-phenyl-9-fluorenol was covalently wired into nanogapped
graphene electrodes to form stable single-molecule junctions. Both
experimental and theoretical studies consistently demonstrate and
interpret the direct measurement of the formation dynamics of individual
carbocation intermediates with a strong solvent dependence in a nucleophilic-substitution
reaction. We also show the kinetic process of competitive transitions
between acetate and bromide species, which is inevitable through a
carbocation intermediate, confirming the classical mechanism. This
unique method creates plenty of opportunities for carrying out single-molecule
dynamics or biophysics investigations in broad fields beyond reaction
chemistry through molecular design and engineering