Copper incorporation in Mn2+-doped Sn2S3 nanocrystals and the resultant structural,optical, and electrochemical characteristics

Sn₂S₃ nanocrystals (NCs) with both Mn²⁺ doping and Cu²⁺ incorporation were synthesized using a chemical bath deposition method. The Cu²⁺ ions formed an anorthic Mn²⁺-doped Cu₂SnS₃ structure with E_g =?1.44?eV, which altered the material's optical and photo/electrochemical properties. After coating the bare Nb₂O₅ electrode with Mn²⁺-doped Sn₂S₃ or Mn²⁺-doped Cu₂SnS₃ NCs, the photoluminescence spectrum was blue-shifted to 411.13?nm from 411.69?nm. Compared to the sample without Cu²⁺, the Cu²⁺-incorporated sample showed a slightly stronger emission at the same position, possibly due to disorder in the crystalline structure based on variations at the interface of Mn²⁺-doped Cu₂SnS₃ NCs. Electrochemical analysis showed a lower charge transfer resistance in the Mn²⁺-doped Cu₂SnS₃, which is related to its larger electroactive surface area. The larger electroactive surface area is attributed to the Faradaic redox processes at the electrode surface, which suppresses the carrier recombination. The coexistence of Cu²⁺ and Mn²⁺ ions shortened the electron transport pathway at the interface and improved the carrier diffusion coefficient and diffusion length, leading to a higher specific capacitance that implies higher energy storage performance. Finally, the I-V characteristics of the Mn²⁺-doped Cu₂SnS₃-coated Nb₂O₅ electrode under various light illumination conditions indicated its better efficiency in photoresponse, electron generation, and charge collection, owing to a superior charge transport mechanism. Detailed results were obtained about the charge dynamics in the as-prepared photo/electrochemical devices with Cu²⁺ incorporation in the Mn²⁺-doped SnS₃ electrode.     

Ag2Se quantum-dot sensitized solar cells for full solar spectrum light harvesting

We report on the photovoltaic performance of Ag₂Se quantum-dot (QD) sensitized solar cells. The QDs are grown by the successive ionic layer adsorption and reaction process. The external quantum efficiency (EQE) spectrum of the assembled cells covers the entire solar power spectrum of 350-2500 nm with an average EQE of ∼80% in the short-wavelength region (350-800 nm) and 56% over the entire solar spectrum. The effective photovoltaic range is ∼7-14 times broader than that of the cadmium calcogenide system—CdS and CdSe. The photocurrent that Ag₂Se generates is four times higher than that of N3 dye. The best solar cell yields power conversion efficiencies of 1.76% and 3.12% under 99.4% and 9.7% sun, respectively. The results show that Ag₂Se QDs can be used as a highly efficient broadband sensitizer for solar cells.