Two major drawbacks in dye-sensitized solar cells (DSSC) are the narrow spectral response and the short-term stability. Research on development of artificial dyes for a broad frequency response is a ...major field of research today. The work presented here shows a broad response with a natural dye extracted from a Mondo-grass (
Ophiopogon japonicus
) berry. Its range of sensitivity covers the entire visible region and its tail expands to the near infrared. This is a unique situation since many natural dyes containing anthocyanin or carotenoids strongly absorbed only below 600 nm. A TiO
2
based electrode sensitized with Mondo grass berry dye DSSC was tested for its performance. An open circuit photovoltage of 495 mV and a short circuit photocurrent of 0.6 mA/cm
2
were obtained under 1 sun illumination. The broad spectral response from 400 to 750 nm was observed for the Mondo-grass berry dye. A high fill factor of 71% was achieved but energy conversion efficiency was only 0.2% for the cell. Even though cell efficiency is low with this dye, the solar cells have exhibited better stability when compared with that of the Blackberry. The thin layer chromatography results indicate that Mondo-grass berry dye contains a mixture of two or more chemical compounds belonging to both the anthocyanin and the carotenoid families.
Electron donor-acceptor molecular charge transfer complexes (CTCs) formed by alpha-sexithiophene (6T) and tetrafluoro-tetracyano-quinodimethane (F4TCNQ) on a Au(111) surface are investigated by ...scanning tunneling microscopy, spectroscopy, and spectroscopic imaging at 6 K. New hybrid molecular orbitals are formed in the CTCs, and the highest occupied molecular orbital of the CTC is mainly located on the electron accepting F4TCNQ while the lowest unoccupied molecular orbital is predominantly positioned on the electron donating 6T. We observed the conductance switching of F4TCNQ inside CTCs, which may find potential applications in novel molecular device operations.
Performance of Dye-sensitized devices depends on the photon absorption and carrier injection properties of the sensitizer (dye). The orientation of the dye molecule affects the photon absorption ...cross-section, injection efficiency and carrier transport. These effects are studied, using three variants of cyanine dyes in n-TiO2/Dye/p-CuSCN heterojunction. The results show correlation of dye-molecule’s orientation on the short-circuit-photocurrent (Isc). The open-circuit-voltage (Voc) is also subjective. The orientation of the dye molecule influence the photon-harvesting efficiency and obstruct the hole-conductor penetrating onto the working-electrode. Additionally, Cumulative effects of e-e, e-h, spin-coupling and HOMO/LUMO distribution are identified.
The band offset at the interface of a heterojunction is one of the most important parameters determining the characteristics of devices constructed from heterojunction. Accurate knowledge of band ...offsets and their temperature dependence will allow one to simulate and predict the device performances. We present a temperature-dependent internal-photoemission spectroscopy (TDIPS) for studying the band offsets. Applications of the TDIPS into III–V and II–VI materials are discussed.
Purpose
The tourism industry has been extensively affected by numerous disasters throughout its history including 30 decades of ethnic war, the tsunami disaster in 2004 and the Easter Sunday attack ...in 2019 substantially impacted the resources and capacities of the tourism industry in Sri Lanka. This study aims to explore the impact of COVID-19 on Sri Lanka as a tourism destination and the tourism industry as a resilient sector of the economy.
Design/methodology/approach
This qualitative study was conducted from July 2020 to September 2020 focusing on the perspectives of multi-level stakeholders in the tourism and hospitality industry in three distinct areas of Sri Lanka, namely, the coastal area, hill country and cultural triangle. The data were collected from 15 stakeholders via semistructured interviews. Convenience sampling method was used to choose the sample and thematic analysis was occupied to meet the study objectives.
Findings
This study will help to reframe the resources and capacities of the country as an emerging destination identifying the diverse credentials from the perspective of different stakeholders to embed the essential resilience after the pandemic.
Research limitations/implications
The prevailing lockdown situation and travel restrictions within the country was a huge challenge during the data collection process. Further to that, the respondents were reluctant to meet outsiders owing to the health threat, and hence some important stakeholders were missing from the study.
Originality/value
This study proposes effective measures to build up a robust destination, necessary strategic planning for policymakers and provisions for stakeholders in the industry to address the health and safety of travelers in the case of future potential health epidemics.
A method is developed for electro-deposition of thin films of the conducting polymer polythiocyanogen on conducting tin oxide glass or other conducting substrate by anodic discharge of SCN
− ions ...form a solution KSCN in propylene carbonate. Films are found to be highly stable and resistant to heat and chemical action. SEM pictures indicate that the films are uniform and free of pin hole. Band gap and band positions are determined from optical absorption spectra and Mott–Schottky plots, respectively. A photovoltaic cell is constructed by depositing polythiocyanogen on nanocrystalline films of n-TiO
2 followed by p-CuI to form a heterojunction. Photocurrent action spectra shows that light absorption by polythiocyanogen generates the photovoltaic response. Results suggest that polythiocyanogen could find applications in optoelectronic devices.
Quantum-dot infrared photodetectors have emerged as attractive devices for sensing long wavelength radiation. Their principle of operation is based on absorption of radiation via intersublevel ...transitions in quantum dots. Multiple layers of self-organized ln(Ga)As/Ga(Al)As quantum dots are generally incorporated in the active region of these devices. Three-dimensional quantum confinement allows normal incidence operation. This paper describes a novel variation in the design of these devices which allows a significant reduction of the dark current, high temperature operation and extension of operation to terahertz frequencies. The principle of operation and operating characteristics of this device - the tunnel quantum-dot intersublevel detector - are described. Operation is demonstrated from 6-80 mum at temperatures up to 300 K with acceptable values of peak responsivity (0.1-0.75 A/W) and specific detectivity (10 7 -10 11 cm ldr Hz 1/2 /W -1 , depending on temperature and wavelength).
The interest in Infrared and Ultraviolet detectors has increased immensely due to the emergence of important applications over a wide range of activities. Detectors based on free carrier absorption ...known as Hetero-junction Interfacial Workfunction Internal Photoemission (HEIWIP) detectors and variations of these heterojunction structures to be used as intervalence band detectors for a wide wavelength region are presented. Although this internal photoemission concept is valid for all semiconductor materials systems, using a well-studied III–V system of GaAs/AlxGa1-xAs to cover a wide wavelength range from UV to far-infrared (THz) is an important development in detector technology. Using the intervalence band (heavy hole, light hole and split off) transitions for high operating temperature detection of mid Infrared radiation is also discussed. A promising new way to extend the detection wavelength threshold beyond the standard threshold connected with the energy gap in a GaAs/AlxGa1-xAs system is also presented. Superlattice detector technology, which is another promising detector architecture, can be optimized using both Type I and Type II heterostructures. Here the focus will be on Type II Strained Layer (T2SL) Superlattice detectors. T2SL Superlattices based on InAs/(In,GA)Sb have made significant improvements demonstrating focal plane arrays operating around 80K and with multiple band detection capability. A novel spectroscopic method to evaluate the band offsets of both heterojunction and superlattice detectors is also discussed.
PDF
