Rising atmospheric levels of carbon dioxide and the depletion of fossil fuel reserves raise serious concerns about the ensuing effects on the global climate and future energy supply. Utilizing the abundant solar energy to convert CO2 into fuels such as methane or methanol could address both problems simultaneously as well as provide a convenient means of energy storage. In this Review, current approaches for the heterogeneous photocatalytic reduction of CO2 on TiO2 and other metal oxide, oxynitride, sulfide, and phosphide semiconductors are presented. Research in this field is focused primarily on the development of novel nanostructured photocatalytic materials and on the investigation of the mechanism of the process, from light absorption through charge separation and transport to CO2 reduction pathways. The measures used to quantify the efficiency of the process are also discussed in detail.

Self-organization of liquid crystalline and crystalline-conjugated materials has been used to create, directly from solution, thin films with structures optimized for use in photodiodes. The discotic liquid crystal hexa-peri-hexabenzocoronene was used in combination with a perylene dye to produce thin films with vertically segregated perylene and hexabenzocoronene, with large interfacial surface area. When incorporated into diode structures, these films show photovoltaic response with external quantum efficiencies of more than 34 percent near 490 nanometers. These efficiencies result from efficient photoinduced charge transfer between the hexabenzocoronene and perylene, as well as from effective transport of charges through vertically segregated perylene and hexabenzocoronene pi systems. This development demonstrates that complex structures can be engineered from novel materials by means of simple solution-processing steps and may enable inexpensive, high-performance, thin-film photovoltaic technology.

No abstract

In TiO2-based dye-sensitized nanocrystalline solar cells, efficiencies of up to 11% have been obtained using Ru dyes, but the limited availability of these dyes together with their undesirable environmental impact have led to the search for cheaper and safer organic-based dyes. In this Letter, we report the synthesis, electronic, and photovoltaic properties of novel green porphyrin sensitizers. All six porphyrin dyes give solar cell efficiencies of ≥5%, but the best performing dye under standard global AM 1.5 solar conditions gives a short circuit photocurrent density (j sc) of 14.0 ± 0.20 mA/cm2, an open circuit voltage of 680 ± 30 mV, and a fill factor of 0.74, corresponding to an overall conversion efficiency of 7.1%, which, for porphyrin-based sensitizers, is unprecedented. This same dye gives an efficiency of 3.6% in a solid-state cell with spiro-MeOTAD as the hole transporting component, comparable to solid-state cells incorporating the best performing ruthenium dyes.

The ruthenium complex bis-tetrabutylammonium cis-dithiocyanato-N,N'-bis-2,2'-bipyridine-4-carboxylic acid, 4'-carboxylate ruthenium(II), N-719, was found to block the dark current of dye sensitized solar cells (DSC), based on mesoporous TiO2 films deposited on a F-doped tin oxide electrode and the effect was compared to surface treatment by TiCl4 and the introduction of a compact TiO2 blocking layer.

This Progress Report highlights recent developments in dye‐sensitized solar cells composed of both liquid electrolytes and solid‐state hole transport materials. The authors discuss and review the present understanding of and recent developments in the operational processes, such as charge generation, transport, recombination, and charge collection. Also, the merits and challenges of alternative device approaches are discussed, including extremely thin absorber cells, devices containing inorganic p‐type hole‐transporters and non‐TiO2 mesoporous metal‐oxide electrodes employed in dye‐sensitized solar cells.

We quantify activation energy, concentration, and diffusion coefficient of mobile ions in MAPbI3 perovskite solar cells using transient ion-drift measurements.

This article reviews the various hole transporting materials (HTMs) used in perovskite solar cells (PSCs) in achieving high photo conversion efficiency (PCE) and operational stability. The PSCs are the latest development in solution processable solar cells offering PCE (~22%) on a par with that of practically deployed silicon and thin film solar cells. HTMs and electron transporting materials (ETMs) are important constituents in PSCs as they selectively transport charges within the device, influence photovoltaic parameters, determine device stability and also influence its cost. This article critically approaches role of structure, electrochemistry, and physical properties of varied of choice of HTMs categorized diversely as small and long polymers, organometallic, and inorganic on the photovoltaic parameters of PSCs conceived in various device configurations. Achievements in tailoring the properties of HTMs to best fit for PSCs are detailed; a well designed HTM suppresses carrier recombination by facilitating the passage of holes but blocking electrons at the HTM/perovskite interface. Moreover, in many PSCs the HTM acts as the first line of defense to external degrading factors such as humidity, oxygen and photon dose, the extent of which depends on its hydrophobicity, permeability, and density.