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Hierarchical dendritic PbS films were deposited on fluorine doped tin oxide (FTO) glass substrates as counter electrodes (CE) for quantum dot-sensitized solar cells (QDSSCs) by a facile one-step pulse voltage electrodeposition method. The electrodeposition time was the key factor to obtain the hierarchical dendritic PbS films. The morphology and the structure of the as-prepared films under different electrodeposition times were investigated by XRD, SEM, TEM and EDS. The results showed that perfect hierarchical dendritic PbS films could be obtained at an electrodeposition time of 20 s. The electrocatalytic and photovoltaic properties of these films as CEs for QDSSCs were evaluated by electrochemical impedance spectroscopy (EIS), Tafel polarization measurements, CV cycling and J–V curves. The hierarchical dendritic PbS exhibits superior catalytic activity and stability in the polysulfide electrolyte, and significantly improved the performance of CdS/CdSe co-sensitized solar cells. An optimized power conversion efficiency (PCE) of 5.76% was achieved, and the QDSSCs were stable for over 24 h. The present study provides a simple pathway to obtain an efficient CE for the QDSSCs. [ABSTRACT FROM AUTHOR]

Further development of solid-state dye-sensitized solar cells (ssDSSCs) requires good fill factor as well as high photon to electron conversion efficiency. We synthesized a pyrazolium-based dication organic ionic conductor with good thermal stability and high ionic diffusion coefficient, Py2C6. This pyrazolium-based electrolyte for ssDSSC achieves an efficiency of 7.30% with a fill factor of up to 79.6% and an open-circuit voltage of 779 mV, which are superior to the respective parameters reported in the previous literature. The obtained cell was characterized by electrochemical impedance spectra (EIS), cyclic voltammetry (CV) and Tafel plot. The results show 24.43 Ω series resistance and 3.31 kΩ shunt resistance, very close to the values for the device with a frequently used liquid-state electrolyte, and these are the major contributors to the high fill factor. The back reaction of photoelectrons at the TiO2/electrolyte interface can also be markedly restrained as a result of the large recombination resistance, thus prolonging the electron lifetime. These factors, together with the remarkable catalytic activity of the counter electrode, lead to good photovoltaic parameters of the cell containing Py2C6. In stability tests, this device shows excellent long-term stability, maintaining 92% of the initial efficiency after 1000 h. [ABSTRACT FROM AUTHOR]

A graphite powder (GP) film-supported Cu2S counter electrode (CE) has been prepared by an accessible and low-temperature method. GP film is prepared using a doctor-blading technique on an F-doped SnO2 conducting glass (FTO) substrate, while Cu2S is formed by immersion and heat treatment of a metal chalcogenide complex (N4H9Cu7S4) in an air atmosphere. GP films provide large areas for the loading of the flake-like catalytic active Cu2S particles. The lamellar structures of GP also provide an excellent electrical pathway for faster charge transportation from the external circuit to the catalyst, Cu2S. Electrochemical impedance spectroscopy and Tafel characterizations indicate that the GP film-supported Cu2S CE constructed using three Cu2S deposition cycles (GP-3Cu2S) exhibits a much smaller charge transfer resistance (Rct) and higher catalytic activity than Pt or bare Cu2S. The quantum dot-sensitized solar cells (QDSSCs) with GP-3Cu2S CEs have a photovoltaic conversion efficiency (PCE) of 4.59%. Moreover, the cells with GP-xCu2S CE exhibit excellent stability under conventional working conditions for 12 h without any obvious decay in the PCE. In contrast, the PCE degrades severely for cells based on Pt or bare Cu2S. [ABSTRACT FROM AUTHOR]

Sea-urchin shaped γ-MnO2hierarchical structures have been synthesized using a facile hydrothermal method without employing any template or surfactant with mild conditions. The as-synthesized samples were characterized by instrumental analyses such as XRD, SEM, and EDXS. γ-MnO2sea-urchins are assembled from nanowires of 20–50 nm in width and up to 3 μm in length. Electrochemical investigations indicate that the sea-urchin shaped γ-MnO2hierarchical nanostructures exhibit favorable performance compared to commercial manganese dioxide as cathode active materials in rechargeable Li–MnO2cells. The sample retains a performance of 101 mA h g−1after 20 charge/discharge cycles. [ABSTRACT FROM AUTHOR]