Atomic Layer Deposition for Sensitized Solar Cells: Recent Progress and Prospects

Abstract

of which are necessary for the successful commercialization of sensitized solar cell (SSC).This report discusses recent progress in using ALD (and MLD) films (red in Table 1) for SSCs, including DSSCs, quantum dot-sensitized solar cells, solid (quasi)-state dye-sensitized solar cells, and perovskite-sensitized solar cells. The first three sections address how ALD can be used to manipulate charge transport in the photoanode, including the creation of core-shell semiconducting scaffolds and the conformal deposition of electrically insulating blocking to control electronic recombination. The next section focuses on synthesizing novel semiconducting scaffolds by ALD to effectively manipulate incident light and charge transport. Next this report describes how ALD can be used to create efficient and stable sensitizers. The final section discusses how ALD can favorably improve cathode materials, especially for electrocatalytic systems. Manipulation of Charge TransportSince the seminal demonstration of O'Regan and Grätzel in the early 1990s, [4] m-TiO 2 (mesoporous TiO 2 ) has become the standard nanostructured semiconducting scaffold of choice for DSSCs. A 10 μm thick m-TiO 2 layer can have a net surface area exceeding 1000× the area of the projected planar surface. Once sensitized, the high surface area of m-TiO 2 permits sufficient light absorption to achieve >10% light-to-electric conversion efficiency. [5] As the efficiencies continue to increase and approach their theoretical limit, more effort is being placed on reducing performance losses across various DSSC interfaces. Major performance losses occur due to charge recombination at the semiconductor/electrolyte and semiconductor/fluorinedoped tin oxide (FTO) interfaces. ALD/MLD has been used to modify these interfaces to both understand fundamental electronic transport phenomena and improve device performance. In the following three subsections, we discuss the use of ALD/ MLD films for manipulating charge transfer kinetics in photoanodes for enhancing overall electron collection efficiency. Core-Shell StructuresCore-shell assemblies are used in DSSCs to manipulate electron transfer processes across the sensitizer/semiconductor interface. Initial demonstrations of core-shell assemblies were Atomic layer deposition (ALD) and molecular layer deposition (MLD) are vapor phase deposition techniques used to create conformal coatings with molecular-level control of thickness and composition. Recently, ALD and MLD have been extensively exploited to engineer the complex interfaces of dye-sensitized solar cells (DSSCs) and other molecularly functionalized photoelectrochemical devices to improve the performance and long-term stability. This progress report describes the recent advances in the applications of ALD and MLD for sensitized solar cells including DSSCs then discusses current challenges and future opportunities of ALD.

Diphenylisobenzofuran Bound to Nanocrystalline Metal Oxides: Excimer Formation, Singlet Fission, Electron Injection, and Low Energy Sensitization

“…Then, because of its long lifetime, the resulting triplet excited state can be harnessed, regardless of the slowed injection rate. The TiO 2 |Al 2 O 3 core–shell metal oxide was prepared by atomic layer deposition (ALD) using alternating cycles of AlMe 3 and H 2 O on a nanocrystalline TiO 2 film . The approximate thickness of the Al 2 O 3 layer is 0.1 nm per cycle …”

“…The TiO 2 | Al 2 O 3 core−shell metal oxide was prepared by atomic layer deposition (ALD) using alternating cycles of AlMe 3 and H 2 O on a nanocrystalline TiO 2 film. 77 The approximate thickness of the Al 2 O 3 layer is 0.1 nm per cycle. 74 Two different dyes were used for the device measurements, 1 and DPPA.…”

High‐Throughput Atomic Layer Deposition of P‐Type SnO Thin Film Transistors Using Tin(II)bis(tert‐amyloxide)

“…Transparent semiconducting metal-oxides have become the foundation of devices such as thin-film transistors (TFTs), solar cells, photodetectors, and memories. [1][2][3][4] The majority of these devices rely on n-type semiconducting compounds (e.g., InGaZnO, InZnO, ZnSnO, and ZnO), for which materials and processes are well established. In contrast, the development of reliable and high performance p-type oxide materials has proven itself to be challenging owing to their inherently high density of interfacial defect states and comparably poor electrical performance, [5] which in turn hampers the effective spatial separation of precursor and coreactant, i.e., the substrate moves underneath injector heads from which either precursor or coreactant are continuously flowing.…”

Functionalized carboxylate deposition of triphenylamine-based organic dyes for efficient dye-sensitized solar cells

“…Because of its nanoporous nature, an adequately sintered mesoporous TiO 2 layer offers a large specic surface area ($1000 times the area of projected planar surface). 17,18 For dipcoating, the solvent carries dye molecules through the nanopores of the nc-TiO 2 lm, in order to allow covalent bonding of the dye to the TiO 2 . 19 Because solution diffusion through nanopores is relatively slow, a long period of time (16-24 h) is necessary to fully sensitize the nc-TiO 2 via dip-coating.…”