Herein, we achieved, air-stable low-temperature processed PSC (L-PSC) using alkali-metal modified ZnO ETLs. Using a simple chemical alkali-metal modification method, the surface defects of the ZnO were effectively passivated. As a result, the interfacial decomposition reactions were suppressed, while raising the Fermi energy level and enhancing electron mobility. The improved interfacial charge transfer and internal electric field in the developed L-PSC using K modified ZnO (ZnO-K) exhibited an improved power conversion efficiency (PCE) of 19.90% with negligible hysteresis, while a pristine ZnO based L-PSC exhibited a PCE of 16.10% with significant hysteresis. The ZnO-K based L-PSC also exhibited remarkably higher long-term air-storage stability (91% retention after 800 h) than pristine ZnO based L-PSCs (36% retention after 800 h) due to the suppressed decomposition reactions. The PCE and air stability of our L-PSC with the modified ZnO are among the highest reported for PSCs processed at ≤150 °C.

Doped perovskite nanocrystals have recently emerged as a new class of energy materials for solar concentrators and solid-state lighting device applications. Among these, doping Mn(II) in high band gap CsPbCl3 perovskite host nanostructures has been extensively studied. However, going beyond their optical emissions, herein, the impact of dopant ions on tuning the doped platelet dimensions and retaining the monodispersity is reported. These were performed by designing appropriate compositions of layered perovskites, L2(Pb1–xMnx)Cl4, which on thermal treatment in the presence of Cs(I) ions transformed to Mn-doped CsPbCl3 platelets. Correlating the amount of Mn present in layered perovskites and retained in doped platelets, the role of Mn for the conversion of layered to doped perovskites was established. These doped platelets showed dominated Mn d–d emission and also Mn concentration-dependent emission tuning. Even though several reports of Mn-doped CsPbCl3 have been reported, these findings add new fundamental insight into the design of dimension-tunable doped perovskites from layered perovskites.

Coordinatively asymmetric or unsaturated metal centers may serve as accessible active sites and allow strong interaction with incoming guests in catalysis, sensing, and separation applications. Herein, a peculiar Co-based phosphate NaCo4(PO4)3, in which all Co atoms were in very rare 5-coordinations, was first synthesized in nanoribbon morphology. With the combined merits of the unique Co coordination, intrinsic half-metallicity, and nanostructured morphology, NaCo4(PO4)3 nanoribbons were characterized with high efficiency for water oxidation in a neutral electrolyte, remarkably outperforming congeneric phosphates such as Na2CoP2O7 with 4-coordinated Co configurations and even comparable to the benchmark RuO2 nanoparticles. The high catalytic performance validates a great potential in exploiting inorganic nanostructures with coordinatively asymmetric or unsaturated metal centers for energy storage and conversion applications.

The open-circuit voltages (VOC) of hybrid perovskite (HP) solar cells do not increase sufficiently with increasing bandgap (for Eg > 1.70eV). We study the impact of A+ size mismatch induced lattice distortions (in ABX3 structure) on the optoelectronic quality of high-bandgap HPs and find that the highest quality films have high A-site size-mismatch, where large guanidinium (GA) compensates for small Cs to keep the tolerance factor in the range for the perovskite structure. Specifically, we find that 1.84eV bandgap (FA0.33GA0.19Cs0.47)Pb(I0.66Br0.34)3 and 1.75eV bandgap (FA0.58GA0.10Cs0.32)Pb(I0.73Br0.27)3 attain quasi-Fermi level splitting of 1.43eV and 1.35eV, respectively, which is >91% of the Shockley-Queisser limit for both cases. Films of 1.75eV bandgap (FA,GA,Cs)Pb(I,Br)3 are then used to fabricate p-i-n photovoltaic devices that have a VOC of 1.24 V. This VOC is among the highest VOC reported for any HPs with similar bandgap (1.7 to 1.8 eV) and a substantial improvement for the p-i-n architecture, which is desirable for tandems with Si, CIGS, or a low-bandgap HP. Collectively, our results show that non-radiative recombination rates are reduced in (FA,GA,Cs)Pb(I,Br)3 films and prove that FA-GA-Cs alloying is a viable route to attain high VOC in high-bandgap HP solar cells.

We study the interaction of mobile ions and electronic charges to form nonradiative defects during electric biasing of methylammonium lead triiodide (MAPbI3) and formamidinium lead triiodide (FAPbI3) thin films. Using multimodal microscopy that combines in situ photoluminescence and scanning Kelvin probe microscopy in a lateral electrode geometry, we correlate temporal changes in radiative recombination with the spatial movement of ionic and electronic charge carriers. Importantly, we compare trap formation with both charge injecting and blocking contacts. Even though ion migration takes place in both cases, we observe the formation of new nonradiative defects in MAPbI3 only in the presence of injected electrons, suggesting that redox processes play a key role. On the basis of density functional theory (DFT) simulations, we propose that reduction of Pb2+ to Pb0 is responsible for the new defects formed in our films. These results underscore that defect properties in metal halide perovskites are not only determined by the migration of mobile ions but are also highly sensitive to their interaction with injected electronic charge.

Despite the imperative importance in solar cell efficiency, the intriguing phenomena at the interface between perovskite solar cell and adjacent carrier transfer layers are hardly uncovered. Here we show that PbI2/AI-terminated lead iodide perovskite (APbI3; A = Cs+/ methylammonium (MA)) interfaced with the charge transport medium of graphene or TiO2 exhibits a sizable/robust Rashba–Dresselhaus (RD) effect using density functional theory and ab initio molecular dynamics (AIMD) simulations above the cubic-phase temperature. At the PbI2-terminated graphene/CsPbI3(001) interface, ferroelectric distortion toward graphene facilitates an inversion breaking field. At the MAI-terminated TiO2/MAPbI3(001) interface, the enrooted alignment of MA+ toward TiO2 by short-strong hydrogen bonding and concomitant PbI3 distortion preserve the RD interactions even above 330 K. The robust RD effect at the interface even at high temperatures, unlike in bulk, changes the direct-type band to indirect-type to suppress recombination of the electron and hole, thereby letting these accumulated carriers overcome the potential barrier between perovskite and charge transfer materials, which promotes the solar cell efficiency.

In this work, the highly selective and stable electrocatalytic reduction of CO2 to CO on nanostructured Ag electrocatalysts is presented. The Ag electrocatalysts are synthesized by the electroreduction of Ag2CO3 formed by in situ anodic-etching of Ag foil in a KHCO3 electrolyte. After 3 min of this etching treatment, the Ag2CO3-derived nanostructured Ag electrocatalysts are capable of producing CO with up to 92% Faradaic efficiency at an overpotential as low as 290 mV, which surpasses all of the reported Ag catalysts at identical conditions to date. In addition, the anodic-etched Ag retained ∼90% catalytic selectivity in the electroreduction of CO2 to CO for more than 100 h. The Ag2CO3-derived Ag is able to facilitate the activation of CO2 via reduction of the activation energy barrier of the initial electron transfer and provide an increased number of active sites, resulting in the dramatically improved catalytic activity for the reduction of CO2 to CO.

Realization of colloidal quantum dot (CQD)/organic photovoltaic (OPV) tandem solar cells that integrate the strong infrared absorption of CQDs with large photovoltages of OPVs is an attractive option toward high-performing, low-cost thin-film solar cells. To date, monolithic hybrid tandem integration of CQD/OPV solar cells has been restricted due to the CQD ink’s catastrophic damage to the organic subcell, thus forcing the low-band-gap CQD to be used as a front cell. This suboptimal configuration limits the maximum achievable photocurrent in CQD/OPV hybrid tandem solar cells. In this work, we demonstrate hybrid tandem solar cells employing a low-band-gap CQD back cell on top of an organic front cell thanks to a modified CQD ink formulation and a robust interconnection layer (ICL), which together overcome the long-standing integration challenges for CQD and organic subcells. The resulting tandem architecture surpasses previously reported current densities by ∼20–25% and yields a state-of-the-art power conversion efficiency (PCE) of 9.4%.

Developing a high-performance sulfur host is central to the commercialization and general development of lithium–sulfur batteries. Here, for the first time, we propose the concept of dynamic hosts for lithium–sulfur batteries and elucidate the mechanism through which TiS2 acts in such a fashion, using in situ X-ray diffraction and cryogenic scanning transmission electron microscopy (cryo-STEM). A TiS2–S composite electrode delivered a reversible capacity of 1120 mAh g–1 at 0.3 C after 200 cycles with a capacity retention of 97.0% and capacities of 886 and 613 mAh g–1 at 1.0 C up to 200 and 1000 cycles, respectively. Our results indicate that it is LixTiS2 (0 < x ≤ 1), rather than TiS2, that effectively traps polysulfides and catalytically decomposes Li2S.

Revealing the exact roles of nitrogen configurations and precise control of the nitrogen configuration in nitrogen-doped graphene (NG) are extremely important for realizing its advanced functions in clean energy technologies. Herein, for the first time, we established that the hydrogen evolution reaction (HER) activities of NG display definite trends due to its nitrogen configurations, which were selectively generated by using layer-structured montmorillonite (MMT) with different layer distances and functions modulated by Co2+, Ni2+, Na+, and H+ ions. We found that among the three types of N, i.e., pyridine, pyrrolic, and quaternary N, quaternary N is the most active one for HER in a metal-free NG catalyst, whereas with an introduction of trace atomic cobalt, the planar (pyridine and pyrrolic) N becomes the better one. In contrast, when trace atomic Ni is involved to replace the Co, the former results in heavily depressed HER activities for the NG catalyst. Density functional theory calculations further revealed that (i) the carbon atoms are highly activated for HER by the nearby quaternary N but not by planar N and (ii) nickel blocks but cobalt promotes the hydrogen adsorption after coordination with planar N, leading to an excellent HER performance.