Inkjet printing of TiO2 potentially offers a high degree of control over the deposition of TiO2 suspensions. Previous use of inkjet printing for TiO2 depositions have focused on producing TiO2 films with uniform density. A multi-ink printing system offers the possibility of depositing TiO2 films with variable density using a single deposition method.

For this research, inkjet printing of TiO2 films with a graded density profile was explored as a means of improving dye sensitized solar cells (DSSCs) performance. Varying pore volume as a means to produce density variations in TiO2 layers was explored. To control the pore volume, several TiO2 suspensions were developed with different pore-forming additives. DSSCs with printed TiO2 films having three density layers showed an average improvement in the conversion efficiency of 127% versus those with a single layer and 45% versus those with dual- layer TiO2. Short-circuit current densities of cells with tri-layer films increased an average of 62% over those with a single layer and 17% over those with dual-layer TiO2. It was also shown that DSSCs with inkjet printed TiO2 layers performed better than those with spin-coated TiO2 layers.

The results effectively demonstrated the potential for using inkjet printing as a sole deposition method to produce TiO2 films with non-uniform density leading to improved DSSC performance. One possibility for further study is to create further layer variations through simultaneous printing of different suspensions.

Charge generation and transport in CH3NH3PbI3-xClx based mesostructured solar cells are investigated. Time correlated single photon counting analysis proves highly efficient charge generation and provides insights on the structural properties of perovskite films. Photoinduced absorption and transient photovoltage analyses depict a double charge recombination dynamics suggesting the existence of two complementary paths for electron transport, involving either TiO2 and perovskite matrixes. Stark spectroscopy, a powerful tool allowing interface-sensitive analysis, is employed to prove the existence of oriented permanent dipoles, consistent with the hypothesis of an ordered perovskite layer close to the oxide surface. This evidence is also confirmed by first principle DFT calculations. The existence of a structural order, promoted by specific local interactions, could be one of the decisive reasons for highly efficient carriers transport within perovskite films.

Graphene nanoplatelets (GNPs) functionalised with platinum were explored as the active material in a high specific surface area ink. The ink had a transmission at 550nm (T550) = 85% and a charge transfer resistance (Rct) of 6Ω/cm2. Although the Rct is higher than required for laboratory cells having a Jsc of 20mA/cm2 under 1 sun test conditions it is sufficient for industrially produced reverse devices, especially when utilised for indoor applications where light conditions will be lower than 100W/m2. This was demonstrated by reverse illuminated DSC efficiencies with flexible cathodes which were equivalent to cells with sputtered platinum catalysts when subjected to 300W/m2 lighting or less. A modification to the ink, suitable for catalysing a Co2+/3+ electrolyte having an Rct of 2Ω/cm2 and T550= 85% was undertaken. This demonstrates potential for use in high efficiency cobalt mediated DSCs. The work shows that printed graphene catalysts are a versatile low cost replacement to sputtered platinum in reverse illuminated DSCs for dye sensitised solar cells.

To provide a counter electrode with lower-cost and simple production method for dye-sensitized solar cells (DSSCs), we developed polyaniline/graphene nanoplatelet/multi-walled carbon nanotube (PANi/GNP/MWCNT) composite films growing on glass substrates by using chemical/electrochemical deposition method and on fluorine-doped tin oxide (FTO)/glass substrates by using electrochemical deposition method respectively. A proper weight ratio of PANi/GNP/MWCNT (1/0.0030/0.0045) composite film depositing on FTO substrate as counter electrode with sheet resistance of 8.25±0.13 Ω/sq for DSSCs yielded power conversion efficiency (PCE) up to 7.45±0.08%, which has potential to replace the conventional Pt cell (7.62±0.07%). In addition, we also fabricated the DSSCs composed of a proper weight ratio of PANi/GNP/MWCNTs (1/0.0045/0.0060) composite film depositing on glass substrate as counter electrode. The sheet resistance of resulting composite film was 59.34±12.34 Ω/sq. These solar cells with FTO-free counter electrode exhibited a PCE of 2.90±0.09%.

We present rational computational design of phenothiazine dyes for dye-sensitized solar cells containing different five-membered rings (thiophene, furan, and selenophene) by a combined strategy of modified conjugation order and functionalization leading to the quinoidization of the ring. We predict that it is possible to lower the excitation energy by 20% vs. the parent dye by the combination of: change in the conjugation order of the methine unit, its functionalization by the CN group, and replacement of the thiophene ring by furan.

A cross-linked copolymer was designed and synthesized bythe imidation of poly(oxyethylene)-diamine and 4,4’-oxydiphthalic anhydride, and followed by a late-stage curing to generate the cross-linked gels. The copolymers consisting of crosslinking sites and multiple functionalities such aspoly(oxyethylene)-segments, amido-acids, imides, and amine termini, characterized by Fourier Transform Infrared Spectroscopy. After the self-curing at 80 °C, the gel-like material enabled to absorb liquid form of electrolytesin the medium of propylene carbonate(PC), dimethylformamide(DMF),and N-methyl-2-pyrrolidone(NMP).By using a field emission scanning electronic microscope, we observed a 3D interconnected nanochannel microstructure, within which, the liquid electrolytes were absorbed. When the novel polymer gel electrolyte (PGE) was fabricated into a dye-sensitized solar cell (DSSC), an extremely high photovoltaic performance was demonstrated. The PGE, absorbed 76.7 wt% of the liquid electrolyte (soaking in the PC solution) based on the polymer’s weight gave rise to a power conversion efficiency of 8.31%, superior to that (7.89%) of the DSSC with liquid electrolytes. It was further demonstrated that the cell had a long-term stabilityduring the test of 1000hat-rest at room temperature or only slightly decreasing in efficiency of 5%.This is the first time demonstration for a PGE exhibiting a higher performance than its liquid counterpart cell. The observation is ascribed to the suppression of the back electron transfer through the unique morphology of the polymer microstructures.

Hybrid halide perovskites represent one of the most promising solutions toward the fabrication of all solid nanostructured solar cells with improved efficiency and long-term stability. This article aims at investigating the structural properties of the iodide/chloride mixed-halide perovskites and correlating them with the photovoltaic performances of the related sensitized solar cells. We found out that, independently on the components ratio in the precursor solution, Cl incorporation, in a I-based structure, is possible only at relatively low concentration levels (below 3-4%). However, even if the material band-gap remains substantially unchanged, incorporation of Cl as a dopant dramatically improves the charge transport within the perovskite layer, explaining the outstanding performances of meso-superstructured solar cells based on this material.

Recently, major advances have been made in electrolytic and solid state DSSCs through the use of perovskite nanocrystals as a sensitizing agent where power conversion efficiencies of over 12% have been realized [1–3]. Moreover the planar DSSC/PV devices with perovskites used as photoactive absorbers sandwiched between selective electron and hole transport layers have demonstrated record performances. Additionally, the uses of carbon nanotubes (CNTs) as a flexible, transparent, lightweight and robust electrode material have been demonstrated in both DSSC as well as OPV devices. The application of CNTs as a charge collector with perovskite sensitized solid state planar PV and DSSCs is discussed. Performance characteristics of CNTs within perovskite based hybrid OPVs are investigated and the role of CNTs as an efficient charge collector is extended to the inverted geometry.

Exfoliated montmorillonite (exMMT) nanoplatelets are a two-dimensional electrolyte carrying ∼1.78 dissociable monovalent cations per nanometer square. They were fabricated through soap-free emulsion polymerization of poly(methyl methacrylate) in the presence of MMT. Because the dissociated exMMTs are anionic, they were not only capable of gelatinizing 1-methyl-3-propylimidazolium iodide (MPII) ionic liquid-based electrolyte, but also increased the power conversion efficiency of resulting dye-sensitized solar cell (DSSC) from 6 to 7.77%. Recently, we investigated the ionic conductive mechanism of exMMT-gelled MPII ionic liquid-based electrolyte and found that the exMMTs acted like an oxidizing agent for iodide ions (I-). As exMMTs were mixed with MPII, I- ions readily oxidized to I3- and even to I5- ions by losing the electrons. Consequently, the ionic conductivity was significantly increased due to the fact that I-, I3-, and I5- tended to form redox couples that transported faster by way of the Grothus/exchange reaction process.