Single-wall carbon nanotubes (SWCNTs) and perovskite (CsPbBr3) quantum dots (QDs), junctions between the two different materials, form semiconductor heterojunctions that function remarkably well as a photodetector. Perovskite is a mechanically stable and easily customized photovoltaic material that generates an electrical current from sunlight when paired with another material, such as SWCNTs.
According to recent research, the performance of the SWCNT/perovskite QD heterojunction, or the ability to convert light into electricity, is improved by increasing the diameter of the SWCNTs.
In heterojunction films containing perovskite QDs, a group of researchers systematically evaluated the performance effects of varying diameters of SWCNTs a single layer of carbon atoms that forms a hexagonal lattice and is rolled into a seamless cylinder with various band gaps.
Their study indicated that increasing the diameter of SWCNTs improved the responsivity, detectivity and response time of this type of heterojunction film. The enhanced separation and transport of photogenerated excitons, an energy-carrying, neutrally charged electron that combines with a positive electron hole, in the film, may mediate this effect.
The team published the results of their study in Nano Research.
“The alignment between the band gaps of SWCNTs and QDs determines the separation of the photogenerated excitons at the heterogeneous interfaces, while different diameter SWCNTs show different carrier capacity and mobility,” said Huaping Liu, the principal investigator of the study and professor at the Institute of Physics at the Chinese Academy of Sciences in Beijing, China.
“These characteristics determine the photoelectronic performance of SWCNTs/perovskite QDs heterojunction films, making it… important to systematically study the diameter effect of different band gap SWCNTs on the photodetection performance of these films.”
The great improvement in the photoelectric performances in films with larger-diameter SWCNTs is attributed to increasing built-in electric fields at the heterojunction interface of s-SWCNTs semiconducting SWCNTs/QDs…, which drives the separation of hole carriers from photogenerated excitons to s-SWCNTs and rapid transport in SWCNT films.
Huaping Liu
The team investigated the differences in photodetector performance for SWCNT diameters between 1.0 and 1.4 nm. Characteristics of each diameter were assessed by exposing the SWCNT/perovskite QD films to 410 nm light at differing intensities and measuring the current-voltage curves of each film. This data could then be used to determine the photocurrent, photoresponsivity and detectivity at each nanotube diameter.
The diameter of the nanotube and the band gap of SWCNTs are roughly inversely related. The research team noticed an increase in responsivity of nearly one order of magnitude, a 5-fold increase in detectivity, and a 4-fold improvement in reaction speed when SWCNT diameter was increased from 1.0 nm to 1.4 nm. The larger-diameter SWCNTs measured in the study improved carrier capacity and mobility to enhance film performance.
“The great improvement in the photoelectric performances in films with larger-diameter SWCNTs is attributed to increasing built-in electric fields at the heterojunction interface of s-SWCNTs semiconducting SWCNTs/QDs…, which drives the separation of hole carriers from photogenerated excitons to s-SWCNTs and rapid transport in SWCNT films,” said Liu.
To lower material costs, energy consumption, and detector fragility in future electronics, next-generation photodetectors constructed from SWCNTs and QDs are required.
Interestingly, SWCNT monolayer films alone are very inefficient at detecting light, and perovskite QD films are prone to low carrier mobility, responsivity and detectivity. As a thin, bilayer film with improved responsiveness, perovskite quantum dot films improve optical absorption when combined with SWCNT monolayers.
The findings of this work will aid in the design and manufacture of new, high-performance photodetectors needed for optical communications, wearable technology, and other applications in artificial intelligence and medicine.
These experimental results will be specifically used by Liu’s team in the development of photodetectors that are designed for use in highly sensitive artificial vision systems.
