The development of high-performance counter electrodes (CEs) for bifacial dye-sensitized solar cells (DSSCs) using nonplatinum (Pt) material is important to prepare low-cost and high-power conversion efficiency (PCE) DSSCs. In this work, poly(3,4-ethylenedioxythiophene) (PEDOT) CEs were prepared by the electrochemical deposition of PEDOT onto fluorine-doped tin oxide substrates for indoor light application. To obtain a high catalytic and high transparent CE, the thickness of the PEDOT film was controlled. Using Y123 dye and cobalt redox system, the cell performance under different light intensities (200−1000 lx) was studied. The results show that the optimal thickness of PEDOT was 90 nm, which can produce higher diffusivity, higher ionic conductivity, and lower charge transfer resistance at the CE/electrolyte interface. Accordingly, PCEs of 23.98% (200 lx), 25.83% (600 lx), and 26.93% (1000 lx) were achieved for a traditional DSSC photoelectrode containing main layer (ML) and scattering layer (SL). For bifacial cells using a newly developed sandwich photoelectrode with the ML/SL/ML structure, the front-side and rear-side efficiencies under 200 lx illumination were 24.16 and 22.45%, respectively, and the rear-to-front-side efficiency ratio was 93%. These efficiencies were much higher than those obtained using Pt CE.

Power generation in indoor environments is the next step in dye-sensitized solar cell (DSSC) evolution. To achieve this goal, a critical recombination route which is usually inhibited by the TiCl4-derived blocking layers (BLs), that is, charge transfer at the fluorine-doped tin oxide substrate/electrolyte interface, is of concern. In this study, we demonstrate that because of low surface coverage, the conventional TiCl4 BLs are unable to suppress such electron leakage, thus limiting the photovoltaic performance of Co­(bpy)3 2+/3+-mediated DSSCs (bpy = 2,2′-bipyridine) under ambient lighting. On the other hand, by introducing compact BLs prepared by spray pyrolysis, the DSSCs show lower dark current and operate efficiently not only under high-intensity sunlight but also under ambient light conditions. The better blocking function of the compact BL is verified by the cyclic voltammetry; other thin-film preparation methods, except for the common TiCl4 treatment, are anticipated to realize a similar blocking effect. This study illustrates that dense thin film with a predominant blocking function is highly required as the BL for DSSCs under low-light conditions, and this concept will pave the way for more development of indoor DSSCs.

SignificanceSingle-particle characterization of the impact response has unveiled design principles to focus and control stress propagation in macroscopic granular crystalline arrays. We demonstrate that similar principles apply to aqueous monolayers of microparticles excited by localized mechanical pulses. By inducing extreme local deformation rates and tracking the motion of each particle with velocities that reach up to few meters per second, we reveal that a regime of elastic collisions, typically forbidden due to overdamping, becomes accessible. This provides insights on the stress propagation and energy absorption of dense suspensions upon fast deformation rates.

The localization energies, capture cross sections, and storage times of holes in GaSb quantum dots (QDs) are measured for three GaSb/GaAs QD ensembles with different QD sizes. The structural properties, such as height and diameter, are determined by atomic force microscopy, while the electronic properties are measured using deep-level transient spectroscopy. The various QDs exhibit varying hole localization energies corresponding to their size. The maximum localization energy of 800 (650) meV is achieved by using additional Al 0.3 Ga 0.7 As barriers. Based on an extrapolation, alternative material systems are proposed to further increase the localization energy and carrier storage time of QDs. V

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