Solid-state dye-sensitized solar cells using polymeric hole conductors.

The present review presents the application of electronically conducting polymers (conducting polymers) as hole conductors in solid-state dye solar cells (S-DSSCs). At first, the basic principles of dye solar cell operation are presented. The next section deals with the principles of electrochemical polymerisation and its photoelectrochemical variety, the latter being an important, frequently-used technique for generating conducting polymers and hole conductors in DSSCs.

A molecular photosensitizer achieves a V of 1.24 V enabling highly efficient and stable dye-sensitized solar cells with copper(II/I)-based electrolyte.

To develop photosensitizers with high open-circuit photovoltage (V) is a crucial strategy to enhance the power conversion efficiency (PCE) of co-sensitized solar cells. Here, we show a judiciously tailored organic photosensitizer, coded MS5, featuring the bulky donor N-(2',4'-bis(dodecyloxy)-[1,1'-biphenyl]-4-yl)-2',4'-bis(dodecyloxy)-N-phenyl-[1,1'-biphenyl]-4-amine and the electron acceptor 4-(benzo[c][1,2,5]thiadiazol-4-yl)benzoic acid. Employing MS5 with a copper (II/I) electrolyte enables a dye-sensitized solar cell (DSC) to achieve a strikingly high V of 1.

Photoelectrochemical Cells Based on Dye Sensitization for Electricity and Fuel Production.

Dye-sensitized semiconductor oxide photoelectrodes in which light is absorbed by a monomolecular layer of dye chemisorbed on a porous oxide substrate have attracted considerable interest in the last 35 years, mainly for the conversion of sunlight to electricity, in dye-sensitized solar cells (DSSCs) with maximal efficiencies in the range 10-15%, and, most recently, as dye-sensitized photoelectrochemical cells (DSPECs) for the generation of solar fuels. In the latter direction, considerable progress has been achieved but the efficiency is notably lower than for electricity generation. In the present review, the basic physicochemical principles of the DSSC and DSPEC operation are described, several keynote results reported, and the factors limiting the performance and necessitating further research highlighted.

Directly Photoexcited Oxides for Photoelectrochemical Water Splitting.

Artificial photosynthesis promises to become a sustainable way to harvest solar energy and store it in chemical fuels by means of photoelectrochemical (PEC) cells. Although it is intriguing to shift the fossil-fuel-based economy to a renewable carbon-neutral one, which will alleviate environmental problems, there is still a long way to go before it rivals traditional energy sources. Existing solar water-splitting devices can be sorted into three categories: photovoltaic-powered electrolysis, PEC water splitting, and photocatalysis (PC).

Diverging surface reactions at TiO- or ZnO-based photoanodes in dye-sensitized solar cells.

Fast recombination of electrons from semiconductors with the oxidized redox species in the electrolyte represents a major bottleneck in the improvement of ZnO-based dye-sensitized solar cells (DSSCs). While processes at the semiconductor-electrolyte interface are well studied on TiO electrodes, the interactions of the ZnO surface with the electrolyte solution in DSSCs are less explored. This work aims at clarifying the different impact of the two contrasting redox couples I/I or [Co(bpy-pz)] (bpy-pz = bis(6-(1H-pyrazol-1-yl)-2,2'-bipyridine)) in electrolytes containing either no additives or Li ions and/or 4-tert-butlypyridine (TBP) in DSSCs using screen-printed nanoparticulate TiO (NP-TiO) or electrodeposited ZnO (ED-ZnO) photoanodes sensitized with the indoline dye DN216.

Dye sensitized photoelectrolysis cells.

To advance the progress of photoelectrolysis, various promising devices integrated with p- and n-type photocatalysts and dye sensitized photoelectrodes have been systematically studied. This review discusses, from theory to practice, an integration strategy for state-of-the-art dye sensitized solar cells (DSSCs) with potential p- and n-type photo-electrocatalysts or directly with dye sensitized photoanodes and cathodes for hydrogen and oxygen production through water splitting. Thorough insight into the theoretical approach which systematically drives the photoelectrolysis reaction directly or in a coupled mode, with diverse configurations of DSSCs and other photovoltaic (PV) cells, is crucial to understand the underlying fundamental concepts and elucidate trends in such reactions, and will serve as a guide to design new electrocatalysts and their integration with new PV devices, while simultaneously underlining major gaps that are required to address the challenges.

Additives, Hole Transporting Materials and Spectroscopic Methods to Characterize the Properties of Perovskite Films.

The achievement of high efficiency and high stability in perovskite solar cells (PSCs) requires optimal selection and evaluation of the various components. After a brief introduction to the perovskite materials and their historical evolution, the first part is devoted to the hole transporting material (HTM), between photoelectrode and dark counter electrode. The basic requirements for an efficient HTM are stated.

Copper Bipyridyl Redox Mediators for Dye-Sensitized Solar Cells with High Photovoltage.

Redox mediators play a major role determining the photocurrent and the photovoltage in dye-sensitized solar cells (DSCs). To maintain the photocurrent, the reduction of oxidized dye by the redox mediator should be significantly faster than the electron back transfer between TiO and the oxidized dye. The driving force for dye regeneration with the redox mediator should be sufficiently low to provide high photovoltages.

Strategy to Boost the Efficiency of Mixed-Ion Perovskite Solar Cells: Changing Geometry of the Hole Transporting Material.

The hole transporting material (HTM) is an essential component in perovskite solar cells (PSCs) for efficient extraction and collection of the photoinduced charges. Triphenylamine- and carbazole-based derivatives have extensively been explored as alternative and economical HTMs for PSCs. However, the improvement of their power conversion efficiency (PCE), as well as further investigation of the relationship between the chemical structure of the HTMs and the photovoltaic performance, is imperatively needed.

Efficient Blue-Colored Solid-State Dye-Sensitized Solar Cells: Enhanced Charge Collection by Using an in Situ Photoelectrochemically Generated Conducting Polymer Hole Conductor.

A high power conversion efficiency (PCE) of 5.5 % was achieved by efficiently incorporating a diketopyrrolopyrrole-based dye with a conducting polymer poly(3,4-ethylenediothiophene) (PEDOT) hole-transporting material (HTM) that was formed in situ, compared with a PCE of 2.9 % for small molecular spiro-OMeTAD-based solid-state dye solar cells (sDSCs).

Dye-sensitized Solar Cells: New Approaches with Organic Solid-state Hole Conductors.

Solid-state dye-sensitized solar cells (sDSCs) in which a solid organic charge-transfer medium, or hole conductor (HC), is interposed between a dye-coated mesoporous oxide electrode and a conductive counter electrode, have attracted considerable interest as viable alternatives to the more ubiquitous mediator-electrolyte DSC. Of particular importance to efficient operation are, in addition to the useful processes contributing to current generation (light harvesting, electron injection and current collection), the recombinative deleterious processes. The organic HCs are highly reactive toward electrons in the oxide or the conducting glass support, therefore necessitating the inclusion of a carefully prepared thin blocking oxide underlayer support as well as the molecular design of special dark current-suppressing dyes.

Efficient dye regeneration at low driving force achieved in triphenylamine dye LEG4 and TEMPO redox mediator based dye-sensitized solar cells.

Minimizing the driving force required for the regeneration of oxidized dyes using redox mediators in an electrolyte is essential to further improve the open-circuit voltage and efficiency of dye-sensitized solar cells (DSSCs). Appropriate combinations of redox mediators and dye molecules should be explored to achieve this goal. Herein, we present a triphenylamine dye, LEG4, in combination with a TEMPO-based electrolyte in acetonitrile (E(0) = 0.

ZnO@Ag2S core-shell nanowire arrays for environmentally friendly solid-state quantum dot-sensitized solar cells with panchromatic light capture and enhanced electron collection.

A solid-state environmentally friendly Ag2S quantum dot-sensitized solar cell (QDSSC) is demonstrated. The photovoltaic device is fabricated by applying ZnO@Ag2S core-shell nanowire arrays (NWAs) as light absorbers and electron conductors, and poly-3-hexylthiophene (P3HT) as a solid-state hole conductor. Ag2S quantum dots (QDs) were directly grown on the ZnO nanowires by the successive ionic layer adsorption and reaction (SILAR) method to obtain the core-shell nanostructure.

Matrix-assisted laser desorption/ionization mass spectrometric analysis of poly(3,4-ethylenedioxythiophene) in solid-state dye-sensitized solar cells: comparison of in situ photoelectrochemical polymerization in aqueous micellar and organic media.

Solid-state dye-sensitized solar cells (sDSCs) are devoid of such issues as electrolyte evaporation or leakage and electrode corrosion, which are typical for traditional liquid electrolyte-based DSCs. Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most popular and efficient p-type conducting polymers that are used in sDSCs as a solid-state hole-transporting material. The most convenient way to deposit this insoluble polymer into the dye-sensitized mesoporous working electrode is in situ photoelectrochemical polymerization.

Dye-sensitized Solar Cells: New Approaches with Organic Solid-state Hole Conductors.

Solid-state dye-sensitized solar cells (sDSCs) in which a solid organic charge-transfer medium, or hole conductor (HC), is interposed between a dye-coated mesoporous oxide electrode and a conductive counter electrode, have attracted considerable interest as viable alternatives to the more ubiquitous mediator-electrolyte DSC. Of particular importance to efficient operation are, in addition to the useful processes contributing to current generation (light harvesting, electron injection and current collection), the recombinative deleterious processes. The organic HCs are highly reactive toward electrons in the oxide or the conducting glass support, therefore necessitating the inclusion of a carefully prepared thin blocking oxide underlayer support as well as the molecular design of special dark current-suppressing dyes.

Carbazole-based hole-transport materials for efficient solid-state dye-sensitized solar cells and perovskite solar cells.

Two carbazole-based small molecule hole-transport materials (HTMs) are synthesized and investigated in solid-state dye-sensitized solar cells (ssDSCs) and perovskite solar cells (PSCs). The HTM X51-based devices exhibit high power conversion efficiencies (PCEs) of 6.0% and 9.

Solid-state dye-sensitized solar cells based on poly(3,4-ethylenedioxypyrrole) and metal-free organic dyes.

Poly(3,4-ethylenedioxypyrrole) (PEDOP), combined with metal-free organic sensitizers, is efficiently used for the first time as the hole-transporting material in solid-state dye-sensitized solar cells. Devices employing PEDOP as the hole conductor and D35 or D21 L6 as the sensitizer show a ten-times-higher energy-conversion efficiency (of 4.5% and 3.

A quasi-liquid polymer-based cobalt redox mediator electrolyte for dye-sensitized solar cells.

Recently, cobalt redox electrolyte mediators have emerged as a promising alternative to the commonly used iodide/triiodide redox shuttle in dye-sensitized solar cells (DSCs). Here, we report the successful use of a new quasi-liquid, polymer-based electrolyte containing the Co(3+)/Co(2+) redox mediator in 3-methoxy propionitrile solvent in order to overcome the limitations of high cell resistance, low diffusion coefficient and rapid recombination losses. The performance of the solar cells containing the polymer based electrolytes increased by a factor of 1.

Liquid electrolytes for dye-sensitized solar cells.

The present review offers a survey of liquid electrolytes used in dye-sensitized solar cells from the beginning of photoelectrochemical cell research. It handles both the solvents employed, and the prerequisites identified for an ideal liquid solvent, as well as the various effects of electrolyte solutes in terms of redox systems and additives. The conclusions of the present review call for more detailed molecular insight into the electrolyte-electrode interface reactions and structures.