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Antimony selenide (Sb 2 Se 3) possesses great potential in the field of photovoltaics (PV) due to its suitable properties for use as a solar absorber and good prospects for scalability. Previous studies have reported the growth of a native antimony oxide (Sb 2 O 3) layer at the surface of Sb 2 Se 3 thin films during deposition and exposure to air, which can affect the contact between Sb 2 Se 3 and subsequent layers. In this study, photoemission techniques were utilized on both Sb 2 Se 3 bulk crystals and thin films to investigate the band alignment between Sb 2 Se 3 and the Sb 2 O 3 layer. By subtracting the valence band spectrum of an in situ cleaved Sb 2 Se 3 bulk crystal from that of the atmospherically contaminated bulk crystal, a valence band offset (VBO) of − 1.72 eV is measured between Sb 2 Se 3 and Sb 2 O 3. This result is supported by a − 1.90 eV VBO measured between Sb 2 O 3 and Sb 2 Se 3 thin films via the Kraut method. Both results indicate a straddling alignment that would oppose carrier extraction through the back contact of superstrate PV devices. This work yields greater insight into the band alignment of Sb 2 O 3 at the surface of Sb 2 Se 3 films, which is crucial for improving the performance of these PV devices. [ABSTRACT FROM AUTHOR]

Cathodoluminescence is used to measure the recombination velocity of the heterointerfaces between Cu2ZnSnS4 (CZTS) and CuxSnySz, SnS secondary phases precipitated along the grain boundaries as well as ZnS precipitated within the CZTS grain interiors. The CZTS/CuxSnySz and CZTS/ZnS heterointerfaces had recombination velocities smaller than the bulk carrier diffusion velocity while the opposite is true for the CZTS/SnS heterointerface. Secondary phases having crystal structures compatible with CZTS (e.g., ZnS, Cu2SnS3) are likely to form heterointerfaces with small misfit strain and hence low interfacial recombination velocity. The precipitation of such secondary phases along grain boundaries in CZTS provides a novel mechanism for grain boundary passivation. However, it is not known if grain boundary passivating secondary phases would necessarily increase the overall photovoltaic device efficiency since other factors, such as the band gap of the secondary phase compared to the Shockley-Queisser ideal value and the nature of the heterointerface between CZTS (i.e., type-I vs type-II), also affect device operation and must therefore be taken into consideration. [ABSTRACT FROM AUTHOR]

As an absorber in photovoltaic devices, Sb2Se3 has rapidly achieved impressive power conversion efficiencies despite the lack of fundamental knowledge about its electronic defects. Here, we present a deep level transient spectroscopy (DLTS) study of deep level defects in both bulk crystal and thin film device material. DLTS study of Bridgman-grown n-type bulk crystals revealed traps at 358, 447, 505, and 685 meV below the conduction band edge. Of these, the energetically close pair at 447 and 505 meV could only be resolved using the isothermal transient spectroscopy (rate window variation) method. A completed Sb2Se3 thin film solar cell displayed similar trap spectra with traps identified at 378, 460, and 690 meV. The comparable nature of defects in thin film and bulk crystal material implies that there is minimal impact of polycrystallinity in Sb2Se3 supporting the concept of benign grain boundaries. [ABSTRACT FROM AUTHOR]

The candidate photovoltaic absorber antimony selenide Sb2Se3 has been prepared by the commercially attractive close-space sublimation method. Structure, composition, and morphology are studied by x-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Large rhubarb-like grains favorable for photovoltaics naturally develop. The temperature-dependence of the direct band gap is determined by photoreflectance between 20 and 320 K and is well described by the Varshni and Bose–Einstein relations, blue-shifting with decreasing temperature from 1.18 to 1.32 eV. The 300 K band gap matches that seen in high quality single-crystal material, while the 0 K gap is consistent with that found in first-principles calculations, further supporting the array of beneficial photovoltaic properties indicated for this material. [ABSTRACT FROM AUTHOR]