This study investigates novel deposition techniques for the preparation of TiO 2 electrodes for use in flexible dye-sensitized solar cells. These proposed new methods, namely pre-dye-coating and codeposition ultrasonic spraying, eliminate the conventional need for time-consuming processes such as dye soaking and high-temperature sintering. Power conversion efficiencies of over 4.0% were achieved with electrodes prepared on flexible polymer substrates using this new deposition technology and N719 dye as a sensitizer.Flexible dye-sensitized solar cells (DSC) have received considerable attention for use in a wide range of potential commercial applications, such as indoor or mobile devices, as well as for building integrated photovoltaic modules [1][2][3][4][5][6][7] . This can be mainly attributed to the fact that the spectrum of the different dyes used in DSCs fits well with that of indoor lightning sources, as well as indirect sunlight diffused through windows. Indoor devices such as remote sensors and alarm systems using indoor lighting conditions in particular requires a very low power density (0.5-1 mW/cm 2 ) that can be obtained with power conversion efficiency (PCE) of less than 3% 8 . Moreover, the device performance of transparent DSCs can be greater than that of competing transparent amorphous silicon solar cells 9 . Despite these advantages, current fabrication processes for DSCs have intrinsic barriers that hinder their use in the continuous mass production of DSC modules using speedy roll-to-roll methods. The first of these is the time-consuming nature of the dye-soaking process, which results from the need to create a high density of dye molecules attached to the surface of TiO 2 nano-particles. Furthermore, this lengthy dye soaking process provides no control over the amount of dye adsorbed on TiO 2 electrodes, which has important implications with regards to device performance and reproducibility. However, as far as we can tell, there have been no reports so far of a dye-soaking process that does allow control over the amount of dye on the TiO 2 surface, nor is there an alternative dye soaking method available that is fast enough to be compatible with speedy roll to roll fabrication. The other critical issue preventing mass production is that the high-temperature (> 450 °C) of the sintering process needed to enhance electrical contact between TiO 2 nanopowder particles (through so-called necking of nano-particles), as well as remove residual solvents and organic binders, is not compatible with flexible polymer substrates due to their thermal degradation at temperatures above 150 °C. Most efforts toward fabricating flexible DSCs have therefore been focused on enhancing the connectivity of TiO 2 electrodes under low-temperature conditions (≤ 150 °C) 2,3,6,[10][11][12][13] . Such research is, however, still far from achieving speedy device fabrication, as it does not eliminate the need for a time-consuming soaking process.

The insertion of lithium into lithium manganese oxide spinel (LiMn 2 O 4 (LMO) to Li 2 Mn 2 O 4 (L 2 MO)) was used to store light energy as a form of chemical energy in a dyesensitized photorechargeable battery (DSPB). Herein, we investigate the effect of crystallite size of LMO on DSPB performance. The crystallite size of graphene-wrapped submicrometer-sized LMO (LMO@Gn) was tuned electrochemically from 26 to 34 nm via repeated LMO-to-L 2 MO transitions. The different crystallite orientations in LMO@Gn particles were ordered in an identical direction by an electric stimulus. The LMO@Gn having a 34 nm crystallite size (L 34 and L 34* ) improved DSPB performances in dim light, compared with the smaller-crystallite LMO@Gn (L 26 ). The overall energy efficiency (η overall ) of 13.2%, higher than ever reported, was achieved by adopting the fully crystallized and structure-stabilized LMO@Gn (L 34* ) for DSPB. The phase transition between the cubic and tetragonal forms during the LMO-to-L 2 MO reaction was suspected to be responsible for the structural ordering.

Dye distribution in a mesoporous TiO film is a key factor in the performance of dye-sensitized solar cells, but there has been little research on it. Here we report even dye distribution within the porous TiO film achieved by a physical driving force of gas flow. Gas-assisted dye arrangement, gas bubbling soaking (GBS), significantly accelerates the dye infiltration compared to conventional overnight soaking (OS). As a demonstration, we investigated the time-dependent dye infiltration using plasmon sensors. GBS produces an even vertical dispersion throughout the film, as illustrated by time-of-flight secondary ion mass spectrometry depth profiles. For devices using a 7-μm-thick active layer and a ruthenium-based dye (N719), only 15 min of GBS treatment produced better power conversion efficiency (PCE) than the optimal result from OS treatment (15 h), despite a lower dye capacity. Dual-GBS treatment (20 min for N719 and 10 min for YD2, a porphyrin dye) produced the best PCE (9.0%) in the device, which was ∼17% higher than that treated with dual-OS (10 h for N719 and 5 h for YD2). Such improvements are associated with reduced dye-free sites inside the porous TiO film after GBS treatment, leading to faster charge transport and slower charge loss.

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The penetration level of the renewable energy resources has been expected to increase rapidly in several years as government has strongly encouraged those through various policies such as the RPS (Renewable Portfolio Standards) and feed-in tariffs. Because the performance of power system is sometimes critically constrained by stability characteristics, it is very challenging for system operator to realize such a high penetration of the renewable energy resources in power system. It has been proposed that the large-scale Energy Storage Systems (ESS) can be applied to the power system for stabilizing the power supply and improving the energy efficiency ratio by using the stored electrical power in the period of high demand for electricity. To implement the large capacity and improve the effectiveness of the lithium-ion battery ESS, it has been constructed 4MW/8MWh ESS test-bed and developed the operation technology of ESS. In this paper, a demonstration study scheme on the large-scale Battery Energy Storage System (BESS) is proposed to verify the effectiveness and to estimate the performance of BESS.