Environment-friendly flexible Cu2ZnSn(S,Se)4 (CZTSSe) solar cells show great potentials for indoor photovoltaic market. Indoor lighting is weak and multi-directional, thus the researches of photovoltaic device structures, techniques and performances face new challenges. Here, we design symmetrical bifacial CZTSSe solar cells on flexible Mo-foil substrate to efficiently harvest the indoor energy. Such devices are fabricated by double-sided deposition techniques to ensure bifacial consistency and save cost. We report 9.3% and 9% efficiencies for the front and back sides of the flexible CZTSSe solar cell under the standard sun light. Considering the indoor environment, we verify weak-light response performance of the devices under LED illumination and flexibility properties after thousands of bending. Bifacial CZTSSe solar cells in parallel achieve the superposition of double-sided output current from multi-directional light, significantly enhancing the area utilization rate. The present results and methods are expected to expand indoor photovoltaic applications.

Robust fluoride-free translucent superhydrophobic coatings were constructed on glass surfaces via one-step aerosol-assisted chemical vapour deposition technique. There are 9 bounce cycles observed on such hierarchically structured surfaces, which exhibited excellent self-cleaning ability.

The three-dimensional (3D) topological insulator (TI) BiSe exhibits topologically protected, linearly dispersing Dirac surface states (SSs). To access the intriguing properties of these SSs, it is important to distinguish them from the coexisting two-dimensional electron gas (2DEG) on the surface. Here, we use circularly polarized light to induce the inverse spin Hall effect in a BiSe thin film at different temperatures (i.e., from 77 to 300 K). It is demonstrated that the photoinduced inverse spin Hall effect (PISHE) of the top SSs and the 2DEG can be separated based on their opposite signs. The temperature and power dependence of the PISHE also confirms our method. Furthermore, it is found that the PISHE in the 2DEG is dominated by the extrinsic mechanism, as revealed by the temperature dependence of the PISHE.