Sulfide kesterite Cu ₂ ZnSnS ₄ (CZTS) is a promising photovoltaic material with considerable potential for application in single-junction, multi-junction, and tandem solar cells. However, advancements in its certified power conversion efficiency (PCE) have remained slow, primarily due to severe interface recombination, which is a major limitation constraining the overall performance of CZTS solar cells. Here, we report an effective heterojunction interface engineering approach in which the CZTS/(Zn,Sn)O heterojunction is subjected to a controlled annealing treatment under dynamically flowing air atmosphere. This treatment induces Zn and Sn cation lattice diffusion to reconstruct a quasi-epitaxial contact at the intermediate interface. This reconstruction effectively suppresses defect-assisted interfacial carrier recombination and optimizes carrier dynamics by enhancing transport and collection efficiencies. Consequently, we achieved a highest certified efficiency of 11.96% for Cd-free, pure-sulfide CZTS solar cell (bandgap > 1.5 eV) without extrinsic cation alloying. This study provides insights into heterojunction interface optimization and the performance enhancement mechanism in the development of kesterite solar cells.

Antimony selenide (Sb₂Se₃) is emerging as a promising photovoltaic material owing to its excellent photoelectric property. However, the low carrier transport efficiency, and detrimental surface oxidation of the Sb₂Se₃ thin film greatly influenced the further improvement of the device efficiency. In this study, the introduction of tellurium (Te) can induce the benign growth orientation and the desirable Sb/Se atomic ratio in the Te-Sb₂Se₃ thin film. Under various characterizations, it found that the Te-doping tended to form Sb₂Te₃-doped Sb₂Se₃, instead of alloy-type Sb₂(Se,Te)₃. After Te doping, the mitigation of surface oxidation has been confirmed by the Raman spectra. High-quality Te-Sb₂Se₃ thin films with preferred [hk1] orientation, large grain size, and low defect density can be successfully prepared. Consequently, a 7.61% efficiency Sb₂Se₃ solar cell has been achieved with a V_OC of 474 mV, a J_SC of 25.88 mA/cm², and an FF of 64.09%. This work can provide an effective strategy for optimizing the physical properties of the Sb₂Se₃ absorber, and therefore the further efficiency improvement of the Sb₂Se₃ solar cells.

Photoelectrochemical (PEC) water splitting in a pH-neutral electrolyte has attracted more and more attention in the field of sustainable energy. Bismuth vanadate (BiVO₄) is a highly promising photoanode material for PEC water splitting. Additionally, cobaltous phosphate (CoPi) is a material that can be synthesized from Earth’s rich materials and operates stably in pH-neutral conditions. Herein, we propose a strategy to enhance the charge transport ability and improve PEC performance by electrodepositing the in situ synthesis of a CoPi layer on the BiVO₄. With the CoPi co-catalyst, the water oxidation reaction can be accelerated and charge recombination centers are effectively passivated on BiVO₄. The BiVO₄/CoPi photoanode shows a significantly enhanced photocurrent density (J_ph) and applied bias photon-to-current efficiency (ABPE), which are 1.8 and 3.2 times higher than those of a single BiVO₄ layer, respectively. Finally, the FTO/BiVO₄/CoPi photoanode displays a photocurrent density of 1.39 mA cm⁻² at 1.23 V_RHE, an onset potential (V_on) of 0.30 V_RHE, and an ABPE of 0.45%, paving a potential path for future hydrogen evolution by solar-driven water splitting.