Conformal Cu _\textrm2 S‐coated Cu _\textrm2 O nanostructures grown by ion exchange reaction and their photoelectrochemical properties

International audienceno abstrac

Elucidating Mechanistic Details of Photo-Induced Charge Transfer in Antimony Sulfide-Based p‑i‑n Junctions

<p>The initial kinetics and mechanisms of photo-induced charge transfer in photovoltaic materials are critical to the operation of fabricated devices. Despite the importance of charge transfer in the picosecond to nanosecond timescales, mechanistic understanding of these events is still limited. To address this challenge, a series of p-i-n junction samples that comprises fluorine-doped tin oxide (FTO)/TiO2/ZnS/Sb2S3/P3HT layers was prepared by atomic layer deposition (ALD). ALD allows for carefully controlled film thickness in samples that enable systematic evaluation of photo-induced charge-transfer kinetics by transient absorption spectroscopy (TAS). Sb2S3 serves as the intrinsic light absorber, P3HT is the hole acceptor, and TiO2 is the electron acceptor. An extremely thin, electron-blocking layer of ZnS was deposited between Sb2S3 and TiO2 varied in thickness by ALD to create a series of 20 samples that included (1) five different ZnS thicknesses (0, 2, 5, 10, and 15 ALD cycles) and (2) four combinations of layers, always including ZnS/Sb2S3, that built up to the completed stack. These mechanistic studies confirm our proposed mechanism for photo-induced electron and hole transfer and recombination in these p-i-n junction samples and provide predictive insights into the charge-transfer processes that may be most determinant in the operation of completed devices.</p&gt

Spin configuration in isolated FeCoCu nanowires modulated in diameter

Cylindrical Fe28Co67Cu5 nanowires modulated in diameter between 22 and 35 nm are synthesized by electroplating into the nanopores of alumina membranes. High-sensitivity MFM imaging (with a detection noise of 1 µN m-1) reveals the presence of single-domain structures in remanence with strong contrast at the ends of the nanowires, as well as at the transition regions where the diameter is modulated. Micromagnetic simulations suggest that curling of the magnetization takes place at these transition sites, extending over 10–20 nm and giving rise to stray fields measurable with our MFM. An additional weaker contrast is imaged, which is interpreted to arise from inhomogeneities in the nanowire diameter

Post-deposition annealing and interfacial atomic layer deposition buffer layers of Sb2Se3/CdS stacks for reduced interface recombination and increased open-circuit voltages

<p>Currently, Sb2Se3 thin films receive considerable research interest as a solar cell absorber material. When completed into a device stack, the major bottleneck for further device improvement is the open-circuit voltage, which is the focus of the work presented here. Polycrystalline thin-film Sb2Se3 absorbers and solar cells are prepared in substrate configuration and the dominant recombination path is studied using photoluminescence spectroscopy and temperature-dependent current–voltage characteristics. It is found that a post-deposition annealing after the CdS buffer layer deposition can effectively remove interface recombination since the activation energy of the dominant recombination path becomes equal to the bandgap of the Sb2Se3 absorber. The increased activation energy is accompanied by an increased photoluminescence yield, that is, reduced non-radiative recombination. Finished Sb2Se3 solar cell devices reach open-circuit voltages as high as 485 mV. Contrarily, the short-circuit current density of these devices is limiting the efficiency after the post-deposition annealing. It is shown that atomic layer-deposited intermediate buffer layers such as TiO2 or Sb2S3 can pave the way for overcoming this limitation.</p&gt