ABSTRACT
Tin-lead (Sn-Pb) perovskite solar cells (PSCs) with near-ideal bandgap still lag behind the pure lead PSCs. Disordered heterojunctions caused by inhomogeneous Sn/Pb ratio in the binary perovskite film induce large recombination loss. Here, an Sn-Pb perovskite film is reported with homogeneous component and energy distribution by introducing hydrazine sulfate (HS) in Sn perovskite precursor. HS can form hydrogen bond network and coordinate with FASnI3 thus no longer bond with Pb2+ , which reduces the crystallization rate of tin perovskite to the level of lead analog. The strong bonding between SO4 2- and Sn2+ can also suppress its oxidation. As a result, the Sn-Pb PSCs with HS exhibit a significantly improved VOC of 0.91 V along with a high efficiency of 23.17%. Meanwhile, the hydrogen bond interaction network, strong bonding between Sn2+ and sulfate ion also improve the thermal, storage, and air stability of resulting devices.
ABSTRACT
Nickel dichalcogenides, especially Ni3S2, present inferior alkaline and neutral hydrogen evolution activity due to their sluggish water dissociation kinetics. Although these materials hold promise as non-noble metal-based electrocatalysts for the hydrogen evolution reaction (HER) in acidic media, developing efficient strategies to enhance the water dissociation processes of nickel dichalcogenides in alkaline and neutral solutions is also an important area of research. The present work discloses an electrocatalytically inactive copper doping strategy to promote the water adsorption and dissociation process of Ni3S2 (Cu-Ni3S2) nanoparticles supported on nickel foam (NF) towards improving the alkaline and neutral hydrogen evolution reactions. Based on combined density functional theory calculations and electrochemical characterizations, the doping of Cu can accelerate the Volmer step and therefore strengthen the water adsorption/dissociation on the respective Ni sites and S sites during the HER process. As a result, the electrocatalyst exhibits superior and stable HER performance in both 1 M KOH and 1 M phosphate-buffered saline (PBS) solutions, with much lower overpotentials of 121 and 228 mV at a current density of 10 mA cm-2, respectively, in comparison to bare Ni3S2. We therefore conclude that the tailored control of the water adsorption/dissociation capability of Ni3S2 will open significant opportunities for the rational design of alkaline and neutral electrocatalysts from earth-abundant and stable materials.
