The in situ formation of reduced dimensional perovskite layer via post‐synthesis ion exchange has been an effective way of passivating organic‐inorganic hybrid perovskites. In contrast, cesium ions in Cs‐based inorganic perovskite with strong ionic binding energy cannot exchange with those well‐known organic cations to form reduced dimensional perovskite. Herein, we demonstrate that tetrabutylammonium (TBA+) cation can intercalate into CsPbI3 to effectively substitute the Cs cation and to form one‐dimensional (1D) TBAPbI3 layer in the post‐synthesis TBAI treatment. Such TBA cation intercalation leads to in situ formation of TBAPbI3 protective layer to heal defects at the surface of inorganic CsPbI3 perovskite. The TBAPbI3‐CsPbI3 perovskite exhibited enhanced stability and lower defect density, and the corresponding perovskite solar cell devices achieved an improved efficiency up to 18.32 % compared to 15.85 % of the control one.

PCE has reached 25.5% in less than one decade since the first report of all-solid-state PSCs in 2012. [5][6][7] Although remarkable progress has been made in device efficiency, there is still a huge gap toward the theoretical Shockley-Queisser limit efficiency (30.5%). [8] Besides the PCE, the long-term stability of PSCs is of great significance for commercial applications, but it could be affected by the interfacial degradation induced by various stresses. [3,4] In a typical planar n-i-p PSC structure, the perovskite absorber is sandwiched between an electron transport layer (ETL) and hole transport layer (HTL). The interfaces between perovskite and carrier transport layers have been considered crucial for the further improvement of efficiency and stability of PSCs. [9,10] On the one hand, the interfacial defects and imperfect band alignments would result in substantial nonradiative recombination losses and thus compromised PCE. [11,12] On the other hand, the degradation of PSCs derived from both perovskite/HTL interfaces and ETL/perovskite interfaces severely threatens the stability of PSCs. [13][14][15][16] Plenty of research has concentrated on stabilizing perovskite/ HTL interfaces via post-fabrication treatment and HTL modification. [17] However, the concentration of defects accumulating at the buried interface is even higher than that at the top interface, [18] which makes the buried interface equally significant as the top interface. Unfortunately, little attention has been paid to it, which is partly because of the difficulties in fabricating and investigating the buried interface. [19] Moreover, the perovskite film near the ETL interface bears the strongest illumination stress under operational condition. Especially under UV exposure, the photovoltaic (PV) performance of PSCs could drop dramatically with the halogen oxidation and Pb reduction because of the vulnerability of perovskite to UV light. [20,21] This process is further accelerated by the desorption of UV-activated oxygen from ETLs, which also exposes deep-level interfacial defects and thus affecting the charge collection. [22][23][24] Although various strategies have been adopted to modify the ETLs to reduce defects, [25][26][27][28][29] there is little research effort on the interaction between the modified ETLs and perovskite films. Recently, Dong and co-workers reported a perovskite/ ETL interface enhancement strategy where formamidinium iodide incorporated SnO 2 reacts with PbI 2 -excess perovskiteThe buried interface between the perovskite and the electron transport layer (ETL) plays a vital role for the further improvement of power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). However, it is challenging to efficiently optimize this interface as it is buried in the bottom of the perovskite film. Herein, a buried interface strengthening strategy for constructing efficient and stable PSCs by using CsI-SnO 2 complex as an ETL is reported. The CsI modification facilitates the growth of the perovskite film and eff...

Herein, sandwich structured tungsten trioxide (WO3) nanoplate arrays were first synthesized for photoelectrochemical (PEC) water splitting via a facile hydrothermal method followed by an annealing treatment. It was demonstrated that the annealing temperature played an important role in determining the morphology and crystal phase of the WO3 film. Only when the hydrothermally prepared precursor was annealed at 500 °C could the sandwich structured WO3 nanoplates be achieved, probably due to the crystalline phase transition and increased thermal stress during the annealing process. The sandwich structured WO3 photoanode exhibited a photocurrent density of 1.88 mA cm(-2) and an incident photon-to-current conversion efficiency (IPCE) as high as 65% at 400 nm in neutral Na2SO4 solution under AM 1.5G illumination. To our knowledge, this value is one of the best PEC performances for WO3 photoanodes. Meanwhile, simultaneous hydrogen and oxygen evolution was demonstrated for the PEC water splitting. It was concluded that the high PEC performance should be attributed to the large electrochemically active surface area and active monoclinic phase. The present study can provide guidance to develop highly efficient nanostructured photoelectrodes with the favorable morphology.

A bifunctional core/shell cocatalyst with a NiCoP core and a nickel cobalt phosphate (NiCo–Pi) shell is developed to promote photocatalytic hydrogen and oxygen generation over graphitic carbon nitride.

The Ni2P cocatalyst can boost hydrogen generation over TiO2, CdS, and C3N4 photocatalysts, which demonstrates its good catalytic property and general applicability.

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Up to now, most of the highly efficient and stable black-phase FAPbI 3 perovskites are fabricated through one-step deposition using antisolvent, which is not convenient for large-scale fabrication because of its narrow processing windows. [5][6][7] Another commonly used method of two-step sequential deposition has wide processing windows, which offers several advantages for the production of larger modules. But it is somehow difficult to fabricate FAPbI 3 perovskite using this method, which can be ascribed to the difficulty of intercalating FA + with large ionic radius into the [PbI 6 ] 4framework in sequential deposition. This process could also introduce defects in black-phase FAPbI 3 perovskite film, which would lead to undesirable nonradiative recombination. [8] To overcome these drawbacks, methylammonium (MA + ), cesium (Cs + ), and bromide (Br -) ions have been doped into FA-based perovskites via sequential deposition, which can reduce the formation energy of blackphase FAPbI 3 and inhibit the defects, [9][10][11] but these doping strategies introduce some side effects such as enlarged bandgap and potential phase segregation issues. [12][13][14] The double-edged sword effect of lead iodide (PbI 2 ) residue is another issue in sequential deposition. Moderate residual PbI 2 at the grain boundary of perovskite can passivate defects and reduce hysteresis, [15] whereas sometimes the residual PbI 2 can deteriorate the photostability of PSCs. [16,17] Thus, good control on the concentration and distribution of residual PbI 2 also plays a crucial role in the formation of high-quality black-phase FAPbI 3 perovskite on the photovoltaic performance. Herein, we report employing a zwitterion of formamidine sulfinic acid (FSA) to functionalize tin(IV) oxide colloid solution (SnO 2 ) layer for sequential deposition of black-phase FAPbI 3 for highly efficient and stable perovskite photovoltaics. Besides helping with the crystallization of black-phase FAPbI 3 perovskite, the incorporation of FSA zwitterion can rearrange the stack direction, orientation, and distribution of residual PbI 2 to reduce its side effect. The FSA zwitterion also acts as interfacial dipole to enhance the conductivity and decrease the work function of SnO 2 electron-transport layer (ETL). All these advantages Black-phase formamidinium lead iodide (FAPbI 3 ) with narrow bandgap and high thermal stability has emerged as the most promising candidate for highly efficient and stable perovskite photovoltaics. In order to overcome the intrinsic difficulty of black-phase crystallization and to eliminate the lead iodide (PbI 2 ) residue, most sequential deposition methods of FAPbI 3based perovskite will introduce external ions like methylammonium (MA + ), cesium (Cs + ), and bromide (Br -) ions to the perovskite structure. Here a zwitterion-functionalized tin(IV) oxide (SnO 2 ) is introduced as the electrontransport layer (ETL) to induce the crystallization of high-quality black-phase FAPbI 3 . The SnO 2 ETL treated with the zwitterion of formamidine sulfinic ...

The development of efficient noble-metal-free hydrogen evolution catalysts is quite appealing with the aim of providing cost-competitive hydrogen.Herein, nickel sulfides (NiS x ) with tunable NiS/Ni 3 S 4 molar ratios were synthesized via a simple hydrothermal method. Detailed electrochemical studies under neutral conditions indicated that the electrocatalytic property of NiS x catalysts was determined by the composition. Notably, the NiS x sample with the NiS/Ni 3 S 4 molar ratio of 1.0 exhibited the lowest overpotential and charge-transfer resistance. As analyzed from the Tafel plots, the rate determining step of NiS x catalysts for hydrogen generation was the Volmer step, in which the proton adsorption played a key role.Theoretical calculation revealed that NiS and Ni 3 S 4 exhibited the metallic behaviors with different work functions. Consequently, the NiS x sample with the NiS/Ni 3 S 4 molar ratio of 1.0 owned the most adsorbed protons, which led to the highest electrocatalytic property. Meanwhile, NiS x was demonstrated to be efficient cocatalysts to promote photocatalytic hydrogen generation. NiS x /CdS with the S 4 molar ratio of 1.0 showed the best photocatalytic activity with the apparent quantum efficiency of 56.5% at 420 nm. This result was in good agreement with the electrocatalytic activities of NiS x samples, indicating the intrinsic property for efficient hydrogen generation.