Designing the Interface of Carbon Nanotube/Biomaterials for High-Performance Ultra-Broadband Photodetection

Abstract

Inorganic/biomolecule nanohybrids can combine superior electronic and optical properties of inorganic nanostructures and biomolecules for optoelectronics with performance far surpassing that achievable in conventional materials. The key toward a high-performance inorganic/biomolecule nanohybrid is to design their interface based on the electronic structures of the constituents. A major challenge is the lack of knowledge of most biomolecules due to their complex structures and composition. Here, we first calculated the electronic structure and optical properties of one of the cytochrome c (Cyt c) macromolecules (PDB ID: 1HRC ) using ab initio OLCAO method, which was followed by experimental confirmation using ultraviolet photoemission spectroscopy. For the first time, the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of Cyt c, a well-known electron transport chain in biological systems, were obtained. On the basis of the result, pairing the Cyt c with semiconductor single-wall carbon nanotubes (s-SWCNT) was predicted to have a favorable band alignment and built-in electrical field for exciton dissociation and charge transfer across the s-SWCNT/Cyt c heterojunction interface. Excitingly, photodetectors based on the s-SWCNT/Cyt c heterojunction nanohybrids demonstrated extraordinary ultra-broadband (visible light to infrared) responsivity (46-188 A W) and figure-of-merit detectivity D* (1-6 × 10 cm Hz W). Moreover, these devices can be fabricated on transparent flexible substrates by a low-lost nonvacuum method and are stable in air. These results suggest that the s-SWCNT/biomolecule nanohybrids may be promising for the development of CNT-based ultra-broadband photodetectors.

Ultrahigh‐Sensitive Broadband Photodetectors Based on Dielectric Shielded MoTe2/Graphene/SnS2 p–g–n Junctions

“…When the wavelength of the incident light is longer than 1240 nm, the graphene would be the only remaining light absorber. This photogating effect (light‐induced electric field that causes charge doping into a semiconductor) is unique at the interface with semiconductor quantum dots, 2D TMDs, carbon nanotubes or other nanostructures due to the strong quantum confinement and therefore significantly enhanced exciton lifetime in these low‐dimensional nanomaterials . With assistance of the built‐in electric field designed at the interface with these low‐dimensional nanostructures, excitons dissociate into electrons and holes and one of them can be transfer out across the interface.…”

Polarity‐Controlled Attachment of Cytochrome C for High‐Performance Cytochrome C/Graphene van der Waals Heterojunction Photodetectors

“…As the consequence of this charge transfer from Cyt c to graphene, the oppositely charged carriers remain trapped in the biomolecular layer before charge recombination occurs. Based on the theoretical calculation of density of states for Cyt c and experimental confirmation using ultraviolet photoemission spectroscopy, the highest occupied molecular orbital (HOMO) (−7.24 eV) and lowest unoccupied molecular orbital (LUMO) (−4.92 eV) levels of Cyt c can be determined . The valence band offset between Cyt c and pristine graphene Fermi level (−4.6 eV) is about 2.64 eV, which results in a built‐in electric field across the Cyt c/GFET interface to facilitate exciton dissociation to free charge carriers.…”

“…Compared with the inorganic materials used primarily in MOS microelectronics, biomolecules are attractive candidates for high‐performance optoelectronics due to not only their unique electronic and optical properties originated for their complex structures which may not be replicated in synthetic processes, but also the possible control in their bindings in a nonvacuum environment for large‐scale device fabrication. Despite exciting progress made in molecular electronics, main challenges remain in fabrication of the molecular electronic devices. They include (1) complicated and tedious electrode fabrication using advanced lithography on individual molecules and (2) difficulties in implementation of “conventional” diode or transistor designs on molecular devices, such as a p–n type of interface for dissociation of the photoexcited excitons and charge transfer from molecule to electrode .…”

“…Despite exciting progress made in molecular electronics, main challenges remain in fabrication of the molecular electronic devices. They include (1) complicated and tedious electrode fabrication using advanced lithography on individual molecules and (2) difficulties in implementation of “conventional” diode or transistor designs on molecular devices, such as a p–n type of interface for dissociation of the photoexcited excitons and charge transfer from molecule to electrode . Addressing these challenges is paramount to the practical applications of molecular electronics.…”

“…In a recent work of the Cyt c/carbon nanotube bulk heterojunctions, we show an ultrabroadband photodetection from ultraviolet–visible–near infrared can be achieved through the combination of optical absorptions of Cyt c in visible spectrum and carbon nanotubes (CNT) in near infrared. However, the photoresponsivity ( R ) of these devices is limited, with the best R ≈188 A W −1 reported at 400 nm wavelength under 10 V bias voltage . A major hurdle to achieving a higher R is the inefficient charge transport across the Cyt c/CNT network due to intertube junctions between individual Cyt c/CNT building blocks.…”