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In dye-sensitized solar cells (DSSCs) photogenerated positive charges are normally considered to be carried away from the dyes by a separate phase of hole-transporting material (HTM). We show that there can also be significant transport within the dye monolayer itself before the hole reaches the HTM. We quantify the fraction of dye regeneration in solid-state DSSCs that can be attributed to this process. By using cyclic voltammetry and transient anisotropy spectroscopy, we demonstrate that the rate of interdye hole transport is prevented both on micrometer and nanometer length scales by reducing the dye loading on the TiO2 surface. The dye regeneration yield is quantified for films with high and low dye loadings (with and without hole percolation in the dye monolayer) infiltrated with varying levels of HTM. Interdye hole transport can account for >50% of the overall dye regeneration with low HTM pore filling. This is reduced to about 5% when the infiltration of the HTM in the pores is optimized in 2 μm th...

The authors demonstrate a unique low cost process to print 2D, submicron size, and high refractive index nanopillars using a direct colloidal-photolithography process. A well collimated i-line source emitting at 365 nm wavelength illuminates a mono layer of silica microspheres of 1 μm diameter deposited on a photosensitive TiO2-based sol-gel layer. No etching process is needed since this layer is directly UV photo patternable like a negative photoresist. Furthermore, this thin layer offers interesting optical properties (high refractive index and optical transparency) and good mechanical and chemical stability and thus can be directly used as a functional microstructure (for PV or sensor applications, for example). The paper describes the modeling of the electric field distribution below the spheres during the illumination process, the photochemistry of the TiO2 sol-gel layer process, and preliminary results of TiO2 nanopillars of around 200 nm in diameter fabricated on a three-inch substrate.

A new heteroleptic ruthenium complex, coded CYC-B12, incorporating an antenna ligand composed of sequential connections of a thienothiophene conjugated bridge and carbazole hole-transport moiety was prepared. This new sensitizer exhibits a lower energy MLCT band centered at 555 nm with a high molar absorption coefficient of 2.24 x 10(4) M-1 cm(-1). The device sensitized by CYC-B12 in conjunction with a volatile electrolyte shows a high photovoltaic efficiency of 9.4% under an illumination of standard global AM 1.5G sunlight. With a low-volatile electrolyte, the cell based on this new sensitizer shows not only a good conversion efficiency of 8.2% but also excellent durability (>96%) under light soaking at 60 degrees C in a simulated sunlight for 1000 h. The difference in the electron recombination kinetics caused by various liquid electrolytes or aging process is also investigated by employing the transient photoelectrical measurements.

We elaborated a new electrolyte composition, based on butyronitrile solvent, that exhibits low volatility for use in dye-sensitized solar cells. The strong point of this new class of electrolyte is that it combines high efficiency and excellent stability properties, while having all the physical characteristics needed to pass the IEC 61646 stability test protocol. In this work, we also reveal a successful approach to control, in a sub-Nernstian way, the energetics of the distribution of the trap states without harming cell stability by means of incorporating NaI in the electrolyte, which shows good compatibility with butyronitrile. These excellent features, in conjunction with the recently developed thiophene-based C106 sensitizer, have enabled us to achieve a champion cell exhibiting 10.0% and even 10.2% power conversion efficiency (PCE) under 100 and 51.2 mW·cm(-2) incident solar radiation intensity, respectively. We reached95% retention of PCE while displaying as high as 9.1% PCE after 1000 h of 100 mW·cm(-2) light-soaking exposure at 60 °C.

The energy relay dye, 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), was used with a near-infrared sensitizing dye, TT1, to increase the overall power conversion efficiency of a dye-sensitized solar cell (DSC) from 3.5% to 4.5%. The unattached DCM dyes exhibit an average excitation transfer efficiency (ETE) of 96% inside TT1-covered, mesostructured TiO(2) films. Further performance increases were limited by the solubility of DCM in an acetonitrile based electrolyte. This demonstration shows that energy relay dyes can be efficiently implemented in optimized dye-sensitized solar cells, but also highlights the need to design highly soluble energy relay dyes with high molar extinction coefficients.

A novel thiocyanate-free cyclometalleted ruthenium sensitizer for solar cells is designed and developed. Upon anchoring to nanocrystalline TiO(2) films, it exhibits a remarkable incident monochromatic photon-to-current conversion efficiency of 83%. The solar cell employing a liquid-based electrolyte exhibits a short circuit photocurrent density of 17 mA/cm(2), an open circuit voltage of 800 mV, and a fill factor of 0.74, corresponding to an overall conversion efficiency of 10.1% at standard AM 1.5 sunlight. To understand the structural, electronic, and optical properties of the cyclometalleted ruthenium sensitizer, we have investigated using density functional theory (DFT) and time-dependent DFT (TDDFT). Our results show the HOMO is located mostly on ruthenium and cyclometalated ligand, while the LUMO is on 4-carboxylic acid-4'-carboxylate-2,2'-bipyridine. Molecular orbitals analysis confirmed the experimental assignment of redox potentials, and TDDFT calculations allowed assignment of the visible absorption bands. The present findings provide new design criteria for the next generation of ruthenium sensitizers and help foster widespread interest in the engineering of new sensitizers that interact effectively with the I(-)/I(3)(-) redox couple.

This paper investigates how nonuniform generation and inefficient collection of electrons influence the dynamic photocurrent and photovoltage response of nanostructured photoelectrodes. The standard diffusion model theory of small amplitude light intensity modulated photocurrent (IMPS) and photovoltage (IMVS) spectroscopy is refined and generalized to an arbitrary electron generation profile, allowing straightforward coupling to any optical model. Expressions are derived for the local electron concentration and IMPS and IMVS transfer functions, for localized, uniform, and exponential generation profiles. Both limited collection and nonuniform generation of electrons modify the photoelectrode thickness (d) dependence of the characteristic IMPS and IMVS time constants and complicate their interpretation. This can lead to significant overestimation of the electron diffusion coefficient, diffusion length, and collection efficiency when using common approximate relations. With near contact electron generation, theIMPS response exhibits two time constants, only the slower one of which corresponds to electron transport across the film and scales with d. In the presence of this effect it is possible that in case of two equally thick samples, the one with smaller electron diffusion coefficient displays apparently faster electron transport. These errors demonstrated by experimental IMPS data of pressed TiO(2) photoelectrodes can be minimized by using modulated light incident from the counter electrode side and avoided when analyzing the ratio of IMPS at opposite directions Of illumination.