The carrier-type of the emerging photovoltaic Sb2Se3 was evaluated for both thin films and bulk crystals via a range of complementary techniques. X-ray photoelectron spectroscopy (XPS), hot probe, Hall effect, and surface photovoltage spectroscopy showed films and crystals synthesized from the Sb2Se3 granulate material to be n-type with chlorine identified as an unintentional n-type dopant via secondary ion mass spectrometry analysis. The validity of chlorine as a dopant was confirmed by the synthesis of intrinsic crystals from metallic precursors and subsequent deliberate n-type doping by the addition of MgCl2. Chlorine was also shown to be a substitutional n-type shallow dopant by density functional theory calculations. TiO2/Sb2Se3 n–n isotype heterojunction solar cells with 7.3% efficiency are subsequently demonstrated, with band alignment analyzed via XPS.

The physical properties of antimony selenide (Sb 2 Se 3 ) are highly anisotropic. Angle-resolved polarised Raman spectroscopy was employed to characterise oriented crystals and used in conjunction with group theory structural analysis to assign vibrational symmetries to the peaks observed in the Raman spectra.The phonon energies were corroborated via density functional theory (DFT) calculations. Furthermore, a straightforward method is proposed to verify the desirable (001) plane orientation of film growth for device applications via minimisation of the 155 cm À1 peak in the Raman spectrum.

The presence of a lone pair of 5s electrons at the valence band maximum (VBM) of Sb2Se3 and the resulting band alignments are investigated using soft and hard x-ray photoemission...

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 there is minimal impact of polycrystallinity in Sb2Se3 supporting the concept of benign grain boundaries.

Alternatives to lead- and tin-based perovskites for photovoltaics and optoelectronics are sought that do not suffer from the disadvantages of toxicity and low device efficiency of present-day materials. Here we report a study of the double perovskite Cs 2 TeI 6 , which we have synthesized in the thin film form for the first time. Exhaustive trials concluded that spin coating CsI and TeI 4 using an antisolvent method produced uniform films, confirmed as Cs 2 TeI 6 by XRD with Rietveld analysis. They were stable up to 250 °C and had an optical band gap of ∼1.5 eV, absorption coefficients of ∼6 × 10 4 cm –1 , carrier lifetimes of ∼2.6 ns (unpassivated 200 nm film), a work function of 4.95 eV, and a p-type surface conductivity. Vibrational modes probed by Raman and FTIR spectroscopy showed resonances qualitatively consistent with DFT Phonopy -calculated spectra, offering another route for phase confirmation. It was concluded that the material is a candidate for further study as a potential optoelectronic or photovoltaic material.