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Bifacial light-harvesting technology is regarded as one effective strategy to enhance the power output of photovoltaic devices, in which the transparent electrode is crucial to determine the power conversion efficiency when illuminated from rear side. To date, the efficiency enhancement of the state-of-the-art bifacial mesoscopic solar cells is mainly focused on the rational design of high catalytic counter electrode without sacrificing the transparency. The cell performance maximum through increasing electron density at counter electrode surface to enhance its catalytic ability is still a challenging problem. In the current work, bi-tandem carbon quantum dots are made to tailor transparent CoSe counter electrode for bifacial dye-sensitized solar cells, achieving a maximized front power conversion efficiency of 8.54% and a rear efficiency of 6.55% in comparison with 7.87% and 5.03% for carbon quantum dots-free device, respectively. The mechanism behind this increment is stemmed from the photo-excited electrons of bi-tandem carbon quantum dots and therefore realizing the electron accumulation on the counter electrode surface. [ABSTRACT FROM AUTHOR]

Graphical abstract Co/Se and Ni/Se nanocomposite films deposited on FTO glasses via magnetron sputtering are used as counter electrodes in dye-sensitized solar cells, yielding a maximized power conversion efficiency of 6.43%. Highlights: • Co/Se and Ni/Se nano-films are prepared by magnetron sputtering method. • The as-prepared films are employed as CEs for DSSCs. • The DSSC with Co/Se CE delivers a PCE of 6.43%. Abstract Dye-sensitized solar cells are promising solutions to energy and environmental problems. By addressing the high cost of preferred platinum counter electrode, Co/Se and Ni/Se nanocomposite counter electrodes are prepared by magnetron sputtering targets onto fluorine-doped tin oxide glass for dye-sensitized solar cell applications. The binary nanocomposite counter electrodes exhibit superior electrocatalytic activity toward I 3 − reduction compared to pure Ni, Se and Co electrodes. In particular, the dye-sensitized solar cell based on Co/Se counter electrode achieves a power conversion efficiency of 6.43%, which is much higher than 0.87%, 2.91%, 3.77% and 5.23% for Ni, Se, Co and Ni/Se solar cells, respectively. The preliminary results demonstrate it is a promising strategy to prepare robust counter electrodes by magnetron sputtering technique for dye-sensitized solar cells. [ABSTRACT FROM AUTHOR]

Abstract The development of weather-independent photovoltaics is a promising strategy for persistently generating electricity in daytime and night. Herein we build a category of multi-energy integrated bifacial solar cells by making long persistence phosphors (LPPs) tailored transparent counter electrodes. The optimized cell with green-emitting transparent polypyrrole-graphene/PtCo achieves a maximized power conversion efficiency of 8.59% under a simulated sun irradiation (100 mW cm−2, air mass 1.5 global) as well as a dark efficiency of 29.68% when ceasing solar illumination. Moreover, the newly launched photovoltaics can persistently generate power lasting for hours in the dark environments. The current work demonstrates a predictable application of photoelectric engineering for persistent energy harvesting free of sun illumination in future. Graphical abstract Image 1 Highlights • Bifacial DSSCs are made by LPP tailored PPy-graphene/PtCo CE. • LPP releases fluorescence to persistently excite dyes when ceasing sunlight illumination. • The DSSCs can persistently generate electricity in the dark. • The newly launched DSSCs yield maximized dark efficiency as high as 29.68%. [ABSTRACT FROM AUTHOR]