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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]

Determining cost-effective semiconductors exhibiting desirable properties for commercial photoelectrochemical water splitting remains a challenge. Herein, we report a Sb2Se3 semiconductor that satisfies most requirements for an ideal high-performance photoelectrode, including a small band gap and favourable cost, optoelectronic properties, processability, and photocorrosion stability. Strong anisotropy, a major issue for Sb2Se3, is resolved by suppressing growth kinetics via close space sublimation to obtain high-quality compact thin films with favourable crystallographic orientation. The Sb2Se3 photocathode exhibits a high photocurrent density of almost 30 mA cm−2 at 0 V against the reversible hydrogen electrode, the highest value so far. We demonstrate unassisted solar overall water splitting by combining the optimised Sb2Se3 photocathode with a BiVO4 photoanode, achieving a solar-to-hydrogen efficiency of 1.5% with stability over 10 h under simulated 1 sun conditions employing a broad range of solar fluxes. Low-cost Sb2Se3 can thus be an attractive breakthrough material for commercial solar fuel production. While photoelectrochemical water splitting offers an integrated means to convert sunlight to a renewable fuel, cost-effective light-absorbers are rare. Here, authors report Sb2Se3 photocathodes for high-performance photoelectrochemical water splitting devices. [ABSTRACT FROM AUTHOR]

Sodium has shown promise as a p-type dopant in CdTe solar cells but reports of increased acceptor concentrations are typically accompanied by adverse structural and morphological changes. Here we show that these changes, which occur upon chlorine activation in the presence of sodium, are dependent upon the initial grain structure. We find that small grain CdTe films deposited by sputtering undergo extensive recrystallisation following MgCl 2 treatment, whereas large grain CdTe deposited by close space sublimation (CSS) do not. This allowed the effect of NaF on device performance to be studied, which is shown to strongly enhance CdS–CdTe intermixing. This results in lower efficiencies due to inferior junction quality, without any clear change in acceptor concentration. [ABSTRACT FROM AUTHOR]

With a 22.1% efficiency record and the successful results in terms of production yield, CdTe based thin film solar cells are today a competing technology with traditional silicon solar cells. Despite different copper-free back contacts have been applied, Cu is present in all the most performing CdTe devices. On the other hand, it is well known that Cu is a fast diffuser in CdTe, and it heavily influences the devices degradation; thus controlling its concentration is very important. In this paper a study of the influence of copper quantity on the performance of the devices and stability at the back contact is presented. CdTe cells fabricated with a 0.1 nm thick Cu layer are compared to devices fabricated with 2.0, 1.0 and 0.5 nm thick Cu layers. The amount of copper affects the performance and aging of the samples. Moreover an inversion of the bias dependency (solar cells in open circuit or in short circuit under current flow), during the aging, occurs in samples containing a copper layer below a certain thickness, suggesting that another degradation mechanism predominates. • For first time ultrathin Cu layer (0.1 nm) is studied on CdTe superstrate solar cell. • Two different cell degradation behaviours are identified depending on Cu thickness. • Carrier concentration does not drop with the reduction of Cu amount. • Excess of Cu brings to the formation of donor defects that compensate the doping. • A very limited amount of Cu is sufficient to reach the maximum possible doping with Cu. [ABSTRACT FROM AUTHOR]

Incorporation of CdSe layers into CdTe thin film solar cells has recently emerged as a route to improve cell performance. It has been suggested that the formation of lower band gap CdTe (1- x ) Se ( x ) phases following Se diffusion induces bandgap grading which may increase the carrier lifetime and thereby open circuit voltage. In this study we investigate the impact of CdSe incorporation on CdTe solar cell performance. We demonstrate that the standard CdS/CdTe device architecture is incompatible with Se incorporation, owing to large optical losses. An alternative cell structure with an oxide partner layer replacing the CdS with SnO 2 /CdSe/CdTe is developed, leading to cell efficiencies of > 13.5%. The differences in processing required for effective selenium incorporation are investigated with performance improvements resulting from additional post-growth annealing. Finally, other oxides such as TiO 2 , ZnO and FTO are demonstrated to be unsuitable partner layers but highlight that the choice of partner layer is key to further improving the performance. [ABSTRACT FROM AUTHOR]

Interface modification with para -aminobenzoic acid passivated the interface states, causing rapid photoelectron transport through the Sb 2 Se 3 /TiO 2 interface and resulting in high onset potential and photocurrent density in the photocathode for photoelectrochemical water splitting. • Surface defects in Sb 2 Se 3 photocathode limit the photovoltage development. • Interface modification not only passivates the interface states, but also allows rapid photoelectron transport. • Record-high onset potential, photocurrent density, and half-cell solar-to-hydrogen efficiency are achieved. Achieving both high onset potential and photocurrent in photoelectrodes is a key challenge while performing unassisted overall water splitting using tandem devices. We propose a simple interface modification strategy to maximize the performance of polycrystalline Sb 2 Se 3 photocathodes for photoelectrochemical (PEC) water splitting. The para -aminobenzoic acid (PABA) modification at Sb 2 Se 3 /TiO 2 interface enhanced both the onset potential and photocurrent of the Sb 2 Se 3 photocathodes. The surface defects in the polycrystalline Sb 2 Se 3 limited the photovoltage production, lowering the onset potential of the photocathode. Surface restoration using the conjugated PABA molecules efficiently passivated the surface defects on the Sb 2 Se 3 and enabled the rapid photoelectron transport from the Sb 2 Se 3 to the TiO 2 layer. The PABA treated Sb 2 Se 3 photocathode exhibited substantially improved PEC performance; the onset potential increased from 0.35 to 0.50 V compared to the reversible hydrogen electrode (V RHE), and the photocurrent density increased from 24 to 35 mA cm−2 at 0 V RHE. [ABSTRACT FROM AUTHOR]