Binary Sb2Se3 semiconductors are promising as the absorber materials in inorganic chalcogenide compound photovoltaics due to their attractive anisotropic optoelectronic properties. However, Sb2Se3 solar cells suffer from complex and unconventional intrinsic defects due to the low symmetry of the quasi‐1D crystal structure resulting in a considerable voltage deficit, which limits the ultimate power conversion efficiency (PCE). In this work, the creation of compact Sb2Se3 films with strong [00l] orientation, high crystallinity, minimal deep level defect density, fewer trap states, and low non‐radiative recombination loss by injection vapor deposition is reported. This deposition technique enables superior films compared with close‐spaced sublimation and coevaporation technologies. The resulting Sb2Se3 thin‐film solar cells yield a PCE of 10.12%, owing to the suppressed carrier recombination and excellent carrier transport and extraction. This method thus opens a new and effective avenue for the fabrication of high‐quality Sb2Se3 and other high‐quality chalcogenide semiconductors.

Antimony selenide (Sb2Se3) is a promising low-cost and environmental-friendly semiconductor photovoltaic material. The power conversion efficiency of Sb2Se3 solar cells has been improved to be 10% in the past few years. The carrier recombination transfer dynamics are significant factors that impact the Sb2Se3 solar cells efficiency. In this work, carrier recombination on the Sb2Se3 surface and carrier transfer dynamics at the CdS/Sb2Se3 heterojunction interface are systematically investigated by surface transient reflectance. According to the evolution of relative reflectance change "?R" /"R" , the carrier thermalization and band gap renormalization time of Sb2Se3 were determined ranging from 0.2 to 0.5 ps, and carrier cooling time was estimated to be about 3?4 ps. Our results also firstly demonstrate that both free electron and shallow-trapped electron transfer occur at the Sb2Se3/CdS interface after photo excitation. The shallow-trapped electron transfer efficiency was calculated in the range of 30% to 70%, determined by the relaxation of shallow trapped electron to deep energy level trap state s. Our results provide a methodology for interpreting transient reflectance of Sb2Se3, and enhances the understanding on carrier kinetics at Sb2Se3 surface and Sb2Se3/CdS interface.

No abstract

Stacking growth of the InGaAs quantum dots (QDs) on top of a carrier injection layer is a very useful strategy to develop QD devices. This research aims to study the carrier injection effect in hybrid structures with a layer of In0.4Ga0.6As surface quantum dots (SQDs), coupled to an injection layer of either one layer of In0.4Ga0.6As buried QDs (BQDs) or an In0.15Ga0.85As quantum well (QW), both through a 10 nm GaAs thin spacer. Spectroscopic measurements show that carrier capture and emission efficiency for SQDs in the BQD injection structure is better than that of the QW injection, due to strong physical and electrical coupling between the two QD layers. In the case of QW injection, although most carriers can be collected into the QW, they then tunnel into the wetting layer of the SQDs and are subsequently lost to surface states via non-radiative recombination. Therefore, the QW as an injection source for SQDs may not work as well as the BQDs for stacking coupled SQDs structures.

GaSb quantum dots (QDs) have been grown by droplet epitaxy within InAlAs barrier layers on an InP (001) substrate. The droplet growth mode facilitates a larger size (average height ∼4.5 nm) and a lower density (∼6.3 × 10 9 cm -2 ) for the QDs than would be expected for the 4% lattice mismatch between GaSb and InAlAs. A type-II band alignment between the GaSb QDs and the InAlAs barriers is revealed by photoluminescence (PL) through a prominent blue-shift of ∼0.11 eV resulting from a six orders of magnitude increase in excitation power. Further confirmation of the type-II nature of these QDs is found through time-resolved PL studies showing a biexponential decay with a long carrier lifetime of ∼10.9 ns. These observations reveal new information for understanding the formation and properties of GaSb/InAlAs/InP QDs, which may be an optimum system for the development of both efficient memory cells and photovoltaic devices.