Solar cells with PbS quantum dot sensitized TiO2-multiwalled carbon nanotube composites, sulfide-titania gel and tin sulfide coated C-fabric

Exfoliated and water dispersible biocarbon nanotubes for enzymology applications

In this chapter, we report a simple and facile method to armor enzymes with carbon nanotubes (CNTs) which are exfoliated, and debundled using bovine serum albumin (BSA). The fabricated CNT/BSA dispersions are biofriendly, biocompatible, defect-free, and highly stable solutions. BSA gives maximum exfoliation efficiency, exceeding the 4mg/mL of CNT concentration compared to any previous reports. Further, the produced bioCNT dispersions were characterized by UV-visible, Raman, circular dichroism spectroscopy, and scanning electron microscopy (SEM). Exfoliation and debundling of the bioCNT dispersions is possible due to the π-π interaction, hydrogen bonding, hydrophobic interaction, and electrostatic attractive forces driving the adsorption of BSA on CNTs surface. Protein adsorption then makes a highly stable suspension in water that can be stored for a prolonged period. CNT dispersions are stable over a wide range of pH from 3 to 10 and at 4°C or 25°C for more than 2 months. Here, we also report the facile, inexpensive and green-chemistry method to fabricate a buckypaper (CNT paper), composed of the high packing density, self-assembled and randomly oriented bioCNTs, and these assemblies could be used in many emerging applications like air and water purification, nanocomposites, energy storage, and biosensing. Moreover, the CNT dispersions stabilized by BSA were successfully used in enzyme binding and kinetic studies and bound enzyme retained substantial catalytic activity. The current approach may facilitate bulk production of water dispersed CNTs in both academic and industrial laboratories. This is done by a simple method of stirring, which provides new opportunities for a wider range of CNT applications.

Quantum Dot Based Solar Cells: Role of Nanoarchitectures, Perovskite Quantum Dots, and Charge-Transporting Layers

Quantum dot solar cells (QDSCs) are attractive technology for commercialization, owing to various advantages, such as cost effectiveness, and require relatively simple device fabrication processes. The properties of semiconductor quantum dots (QDs), such as band gap energy, optical absorption, and carrier transport, can be effectively tuned by modulating their size and shape. Two types of architectures of QDSCs have been developed: 1) photoelectric cells (PECs) fabricated from QDs sensitized on nanostructured TiO₂ , and 2) photovoltaic cells fabricated from a Schottky junction and heterojunction. Different types of semiconductor QDs, such as a secondary, ternary, quaternary, and perovskite semiconductors, are used for the advancement of QDSCs. The major challenge in QDSCs is the presence of defects in QDs, which lead to recombination reactions and thereby limit the overall performance of the device. To tackle this problem, several strategies, such as the implementation of a passivation layer over the QD layer and the preparation of core-shell structures, have been developed. This review covers aspects of QDSCs that are essential to understand for further improvement in this field and their commercialization.

Quantum Dot Donor-Polymer Acceptor Architecture for a FRET-Enabled Solar Cell

Forster resonance energy-transfer (FRET)-based solution-processed solar cell is fabricated with cadmium sulfide (CdS) as the energy donor and poly[ N-9'-heptadecanyl-2,7-carbazole- alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) as the energy acceptor. Carbon dots (C-dots) deposited on carbon fabric are applied as a counter electrode. Although electron injection from CdS to PCDTBT is energetically disfavored, evidences for energy transfer between the two components of the cell are obtained in terms of FRET parameters with the relative quantum yield of donor CdS quantum dots (QDs) being ∼0.3, a Forster radius of ∼3.7 nm, and an energy-transfer efficiency of ∼55%. Power conversion efficiency (PCE) of the TiO₂/PCDTBT cell without the donor is 0.23% and when coupled with donor CdS QDs, the ensuing TiO₂/PCDTBT/CdS cell experiences a 23 time increment in PCE, reaching 5.3%. The complete FRET cell: TiO₂/PCDTBT/CdS/ZnS-S^2--C-dots/C-fabric produces a PCE of 7.42%, under 1 sun illumination. External quantum efficiency studies reveal an enhanced spectral response spanning from 300 to 670 nm, with 300 and 175% increases attained for the FRET-enabled TiO₂/PCDTBT/CdS/ZnS photoanode compared with the TiO₂/PCDTBT photoanode over the blue and green-red portions of the solar spectrum.