Lead chalcogenides colloidal quantum dot (PbS CQD) solar cells employing an ordered bulk heterojunction (OBHJ) structure allow sufficient utilization of solar energy and at the same time ensure efficient charge extractions. However, the interfacial deficiency was determined to be a significant limiting factor for the further improvement of efficiency. Herein, a finely interpenetrating OBHJ structure between zinc oxide nanowire (ZnO NW) arrays and PbS CQDs was achieved by simultaneously controlling the growth orientation of ZnO NWs and introducing convective assembly as the CQD deposition technique. The inherent directionality during the assembly process leads to dense packing and efficient infiltration of CQDs, forming a valid OBHJ structure. Additionally, a self-assembled monolayer was introduced to further improve the V oc deficit. As a result, a record PCE of 9.92% has been demonstrated for OBHJ structured CQD solar cells that are compatible with low-temperature and scalable manufacturing processes.

Passivating electron‐transporting layers (ETLs) with alkali salts have demonstrated a facial approach that is essential in healing defective surfaces, consequently improving the functionality and stability of perovskite‐based solar cells (PSCs). Herein, the pseudohalide salt of sodium tetrafluoroborate, whose anions have a higher electronegativity than other halide salts (i.e., iodide and chloride), with the potential to passivate the surface of tin oxide while enhancing the optoelectronic properties of a perovskite film, is presented. Meanwhile, the density functional theory calculations show that BF4−/F− ions exhibit a robust ionic interaction with an uncoordinated Sn4+ site. In contrast, the Na ion is bound to an oxygen atom of the OH− group, which helps reduce surface defect states and improves charge transfer properties. Thus, the best PSC exhibits a current density of 23.51 mA cm−2, an open‐circuit voltage of 1.10 V, and an excellent fill factor of 80.48, providing an efficiency of 20.82%, which exceeds that of a control device (18.38%). Importantly, the retention of the power conversion efficiency on NaBF4‐based PSCs without encapsulation is 18.44% after 1000 h of aging under ambient conditions, whereas the retention of a control device is only 16.08%.

Posttreatment of titanium oxide (TiO 2 ) using lithium (Li) and cobalt (Co) precursors is widely adopted to modify the charge quenching property in perovskite solar cells (PSCs); however, the fundamental understanding of the effect of the modification layer on the material itself and, consequently, the photovoltaic performance stability is not complete. In this work, in situ X-ray diffraction measurements show that the Li and Co ions can diffuse into TiO 2 and consequently accelerate the rutile phase transformation. X-ray photoelectron spectroscopy results reveal the appearance of a Ti 3+ feature in both the Li-and Co-treated samples, suggesting that the treatment ions are partially located at the subsurface/surface of the spin-cast TiO 2 layer. The Li-treated TiO 2 exhibits greatly upshifted conduction band edges, which benefits charge extraction properties and improves the average device parameters in a complete PSC. To complement the experiments, density functional theory calculations are performed. While Li treatment initially results in enhanced electronic properties, Li-treated TiO 2 tends to have more surface vacancies over time and is more susceptible to adsorption and accumulation of iodide ions compared to the Co-treated sample, which is experimentally supported by surface photovoltage spectroscopy and timeresolved photoluminescence results.

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