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Herein, we report a sequential deposition procedure to passivate the surface of a hybrid mixed cationic tin perovskite (E1G20) with phenylhydrazinium thiocyanate (PHSCN) dissolved in trifluoroethanol solvent. The photoluminescence lifetime of the PHSCN film was enhanced by a factor of 6, while the charge-extraction rate from perovskite to C60 layer was enhanced by a factor of 2.5, in comparison to those of the E1G20 film. A slow surface passivation was observed; the performance of the PHSCN device improved upon increasing the storage period to attain an efficiency of 13.5% for a current-voltage scan in the forward bias direction. An inverted effect of hysteresis was observed in that the efficiency of the forward scan was greater than that of the reverse scan. An ion-migration model as a result of the effect of the phenylhydrazinium surface passivation is proposed to account for the observed phenomena. The device was stable upon shelf storage in a glovebox for 3000 h.

A polymer-based hole-transporting layer (HTL) with a tunable work function and highest occupied molecular orbital (HOMO) position was demonstrated to effectively optimize the anode junctions of optoelectronic devices. Herein, the perfluorinated ionomer (PFI) was utilized to realize the synthesis of a well-dispersed poly(3,4-ethylene dioxythiophene) (PEDOT) colloid solution, which could be subsequently cast into an efficient HTL. According to the time-of-flight secondary-ion mass spectroscopy and ultraviolet photoelectron spectroscopy analysis, a uniform, interpenetrating PEDOT network with a deep-lying HOMO position could be obtained in the PEDOT:PFI layer. For solar cells, since a deep-lying HOMO position of the HTL was favorable for minimizing the hole injection barrier, a superior organic photovoltaic efficiency of 15.1% and a perovskite solar cell efficiency of 17.8% were achieved. As for organic photodetectors, a deep-lying HOMO position of the HTL was able to reduce the dark current density (JD) by blocking the leakage current under a reverse bias. Utilizing the PEDOT:PFI with an optimized PFI content, an extremely low JD of 6.2 nA cm−2 with an external quantum efficiency of 67% at 1000 nm wavelength was achieved, which sets a benchmark for the emerging near infrared sensing technologies.

Perovskite solar cells (PSCs) employing organic–inorganic hybrid lead perovskite have attracted much attention as promising next generation solar cells because of their low fabrication cost and extremely high power conversion efficiency (PCE). Exploring new perovskite materials and additives is one of the effective strategies to improve the performance of PSCs. Here, we synthesized formamide iodide (FoAI) and applied it as both a cation material and additive. Although it was revealed that FoAI is not incorporated in the A-site of the perovskite structure, we found that the FoAI additive suppresses δ-FAPbI3 formation and improved the performance of FAPbI3 based PSCs. The PCE was improved from 12.29% to 14.49% by adding 5 mol% of FoAI in the precursor solution. Meanwhile, we found that FoAI additive can also improve the performance of triple-cation PSCs. We believe that FoAI is one of the promising additives to boost the PCE of PSCs without any influence on the composition of the perovskite materials.

Unraveling the reaction mechanism behind the CO2 reduction reaction (CO2RR) is a crucial step for advancing the development of efficient and selective electrocatalysts to yield valuable chemicals. To understand the mechanism of zinc electrocatalysts toward the CO2RR, a series of thermally oxidized zinc foils is prepared to achieve a direct correlation between the chemical state of the electrocatalyst and product selectivity. The evidence provided by in situ Raman spectroscopy, X-ray absorption spectroscopy (XAS) and X-ray diffraction significantly demonstrates that the Zn(II) and Zn(0) species on the surface are responsible for the production of carbon monoxide (CO) and formate, respectively. Specifically, the destruction of a dense oxide layer on the surface of zinc foil through a thermal oxidation process results in a 4-fold improvement of faradaic efficiency (FE) of formate toward the CO2RR. The results from in situ measurements reveal that the chemical state of zinc electrocatalysts could dominate the product profile for the CO2RR, which provides a promising approach for tuning the product selectivity of zinc electrocatalysts.

Heterogeneous catalysis based on air-stable lanthanide complexes is relatively rare, especially for electrochemical water oxidation and reduction. Therefore, it is highly desired to investigate the synergy caused by cocatalysts on the lanthanide complex family for heterogeneous catalysis because of their structural diversity, air/moisture insensitivity, and easy preparation under an air atmosphere. Two mononuclear and three dinuclear dysprosium complexes containing a series of Schiff-base ligands have been demonstrated as robust electrocatalysts for triggering heterogeneous water oxidation in alkaline solution, in which the complex [Dy2(hmb)2(OAc)4]·MeCN(3) was revealed to have the best activity toward heterogeneous water oxidation among all five complexes in the present study. The molecular activation of dysprosium complexes has also been investigated with a series of N-containing heterocyclic additives [i.e., 4-(dimethylamino)pyridine (DMAP), bis(triphenylphosphine)iminium chloride ([PPN]Cl), indole, and quinoline]. In particular, the corresponding overpotential was effectively enhanced by 211 mV (at a current density of 10 mA cm-2) with the assistance of DMAP. On the basis of electrochemical and ex situ/in situ spectroscopic investigations, the best catalyst, DMAP-complex 3 on a carbon paper electrode, was confirmed with well-maintained molecular identity during heterogeneous water oxidation free of forming any dysprosium oxide and/or undesired products.

The composite electron transporting layer (ETL) of metal oxide with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) prevents perovskite from metal electrode erosion and increases p-i-n perovskite...

Sol–gel metal oxide films are an important type of functional materials for energy technologies and beyond owing to their versatile properties and ease of processing, but their applications are limited by the typically required high sintering temperatures. This study reports a novel phenomenon where the sintering temperatures of sol–gel metal oxide films were substantially lowered when a metal phase was embedded within the sol–gel precursor films. Morphological and compositional analyses revealed that the reduction in sintering temperatures was enabled by a mechanism similar to the metal-induced crystallization (MIC) process, with a distinction that catalysis of sol–gel reactions occurred alongside the induction of crystallization. We observed this catalytic MIC (c-MIC) mechanism in a variety of sol–gel material systems including NixO with embedded Au or Ag; TiOx with embedded Ni, Au, or Pt; and SnOx with embedded Ni. Based upon this concept, we demonstrated highly efficient flexible and rigid organic/inorganic hybrid perovskite solar cells (PSCs) using a low-temperature-sintered NixO film embedded with Au nanoislands as the hole-transporting layer (HTL). The c-MIC mechanism reduced the sintering temperature of the Au-embedded NixO HTL by 100 °C, making the NixO process compatible with plastic substrates while allowing the NixO HTL to retain more NiOOH surface groups, which enhanced hole collection and improved the quality of the perovskite layer. Thanks to the advantages of the c-MIC NixO film, the flexible and rigid PSCs achieved high power conversion efficiencies of up to 15.9 and 19.0%, respectively, which were sustained for >1200 h at 65 °C and 65% relative humidity. Our findings provide a practical route for low-temperature fabrication of high-quality oxide functional films by solution-based sol–gel processes, which will be valuable to a wide variety of applications in addition to thin film solar cells.

Tin-based perovskite, which exhibits narrower bandgap and comparable photophysical properties to its lead analogs, is one of the most forward-looking lead-free semiconductor materials. However, the poor oxidative stability of tin perovskite hinders the development toward practical application. In this work, the effect of pseudohalide anions on the stability and emission properties of single-layer 2D tin perovskite nanoplates with chemical formula TEA2 SnI4 (TEA = 2-thiophene-ethylammonium) is reported. The results reveal that ammonium thiocyanate (NH4 SCN) is the most effective additive in enhancing the stability and photoluminescence quantum yield of 2D TEA2 SnI4 (23 ± 3%). X-Ray photoelectron spectroscopic investigations on the thiocyanate passivated TEA2 SnI4 nanoplate show less than a 1% increase of Sn4+ signal upon 30 min exposure to air under ambient conditions (298 K, humidity ≈70%). Furthermore, no noticeable decrease in emission intensity of the nanoplate is observed after 20 h in air. The SCN- passivation during the growth stage of TEA2 SnI4 is proposed to play a crucial role in preventing the oxidation of Sn2+ and hence boosts both stability and photoluminescence yield of tin perovskite nanoplates.

NiO is an attractive hole-transporting material for polymer solar cells (PSCs) owing to its excellent stability and electrical/optical properties. This study demonstrates, for the first time, fabrication of uniform, defect-free, and conformal NiO ultra-thin films for use as hole-transporting layers (HTLs) in PSCs by atomic layer deposition (ALD) through optimization of the ALD processing parameters. The morphological, optical, and electrical properties of ALD NiO films were determined to be favorable for their HTL application. As a result, PSCs containing an ALD NiO HTL with an optimized thickness of 4 nm achieved a power conversion efficiency (PCE) of 3.4%, which was comparable to that of a control device with a poly(3,4-ethylenedioxy-thiophene):poly(styrene-sulfonate) HTL. The high quality and manufacturing scalability of ALD NiO films demonstrated here will facilitate the adoption of NiO HTLs in PSCs.