Transparent conductive oxide (TCO) layer-less dye sensitized solar cells (DSCs) are reported. The cell is composed of a glass substrate, TiO2 porous layer stained with dye molecules, porous Ti electrode, electrolyte, and a Pt sputtered Ti sheet. The cell exhibits an efficiency of 7.43% which was a little less than that of 8.44% for a DSC consisting of a TCO glass. The high efficiency was brought about by the thick and porous Ti electrode (200–300nm thickness) which kept high conductivity and swift ionic diffusion. The preparation process for the Ti electrode is reported.

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We study a model eco-system by means of dynamical techniques from disordered systems theory. The model describes a set of species subject to competitive interactions through a background of resources, which they feed upon. Additionally direct competitive or co-operative interaction between species may occur through a random coupling matrix. We compute the order parameters of the system in a fixed point regime and identify the onset of instability and compute the phase diagram. We focus on the effects of variability of resources, direct interaction between species, co-operation pressure and dilution on the stability and the diversity of the eco-system. It is shown that resources can be exploited optimally only in the absence of co-operation pressure or direct interaction between species. This approach has been used to study, for example, the effects of self-interaction and memory in models of financial trading [1,2] or to examine how co-operation pressure and order of interactions impact on the stability and trajectories of replicator systems of evolutionary game theory [5]- [7]. In the context of population dynamics models with random interactions were first addressed by May in [8].In this paper we study a model of a simple food-web composed of species and resources, originally proposed in a more basic form in [9]. The level of the resource consumption by species and its relationship with the stability of the eco-system and the species richness is one of the main issues in ecology [10]. In [9], interaction between species is not through direct interaction (e.g. via prey-predator relations) but exclusively through the use and dependence on resources. If, for example, species A consumes a resource which B feeds upon as well, then this introduces a negative and symmetric interaction between A and B. The strength of the negative interaction between A and B is hence regulated by the overlap in their dependence on resources.Due to the symmetry of interactions the discussion of [9] focuses on a static analysis of this model eco-system. Here we choose a complementary dynamical approach, which allows us to address a broader class of interaction modes. Static studies necessarily rely on the existence of a Lyapunov function, extremized by the trajectories of the eco-system, and are hence limited to systems with symmetric interactions. In the case of an eco-system this is an obvious drawback, as competitive interaction of, for example, prey-predator pairs cannot appropriately be addressed. A direct study of the dynamical equations allows us to extend the analysis to cases of asymmetric interaction matrices, and in particular to discuss the effects of anti-correlation on the behaviour of the system [11,12]. Asymmetric interaction comes in two ways in the present eco-system. Firstly, we introduce direct interaction between species, in addition to the indirect interaction through the use and dependence on resources. Secondly, we study the effects of possibly asymmetric dilution of the network of interacting species.The aim of o...

A transparent conductive oxide-less dye-sensitized solar cell (TCO-less DSC) consisting of a thick and porous Ti electrode is reported. The Ti electrode was contacted with the back of a stained porous titania layer. A thick Ti electrode prepared by conventional sputtering prevented ionic diffusions through the Ti electrode and decreased photovoltaic performance. Tetrapod-shaped ZnO crystals were used to prepare straight and continuous nanopores in the Ti electrode to maintain the ionic diffusion. 8% efficiency of the TCO-less DSC is also reported. #