Defect-induced non-radiative losses are currently limiting the performance of hybrid perovskite devices. Experimental reports have indicated the existence of point defects that act as detrimental ...non-radiative recombination centres under iodine-poor synthesis conditions. However, the microscopic nature of these defects is still unknown. Here we demonstrate that hydrogen vacancies can be present in high densities under iodine-poor conditions in the prototypical hybrid perovskite MAPbI
(MA = CH
NH
). They act as very efficient non-radiative recombination centres with an exceptionally high carrier capture coefficient of 10
cm
s
. By contrast, the hydrogen vacancies in FAPbI
FA = CH(NH
)
are much more difficult to form and have a capture coefficient that is three orders of magnitude lower. Our study unveils the critical but overlooked role of hydrogen vacancies in hybrid perovskites and rationalizes why FA is essential for realizing high efficiency in hybrid perovskite solar cells. Minimizing the incorporation of hydrogen vacancies is key to enabling the best performance of hybrid perovskites.
Despite intense research in past decades, the lack of high-performance catalysts for fuel cell reactions remains a challenge in realizing fuel cell technologies for transportation applications. Here ...we report a facile strategy for synthesizing hierarchical platinum-cobalt nanowires with high-index, platinum-rich facets and ordered intermetallic structure. These structural features enable unprecedented performance for the oxygen reduction and alcohol oxidation reactions. The specific/mass activities of the platinum-cobalt nanowires for oxygen reduction reaction are 39.6/33.7 times higher than commercial Pt/C catalyst, respectively. Density functional theory simulations reveal that the active threefold hollow sites on the platinum-rich high-index facets provide an additional factor in enhancing oxygen reduction reaction activities. The nanowires are stable in the electrochemical conditions and also thermally stable. This work may represent a key step towards scalable production of high-performance platinum-based nanowires for applications in catalysis and energy conversion.
The development of superior non‐platinum electrocatalysts for enhancing the electrocatalytic activity and stability for the oxygen‐reduction reaction (ORR) and liquid fuel oxidation reaction is very ...important for the commercialization of fuel cells, but still a great challenge. Herein, we demonstrate a new colloidal chemistry technique for making structurally ordered PdCu‐based nanoparticles (NPs) with composition control from PdCu to PdCuNi and PtCuCo. Under the dual tuning on the composition and intermetallic phase, the ordered PdCuCo NPs exhibit better activity and much enhanced stability for ORR and ethanol‐oxidation reaction (EOR) than those of disordered PdCuM NPs, the commercial Pt/C and Pd/C catalysts. The density functional theory (DFT) calculations reveal that the improved ORR activity on the PdCuM NPs stems from the catalytically active hollow sites arising from the ligand effect and the compressive strain on the Pd surface owing to the smaller atomic size of Cu, Co, and Ni.
Non‐platinum electrocatalysts for fuel‐cell reactions, composed of ordered intermetallic PdCuM nanoparticles (NPs; M=Ni or Co), have been synthesized. These ordered PdCuM NPs are generally much more active and stable than the conventional disordered counterparts and also the commercial Pt/C and Pd/C catalysts, towards both the ethanol‐oxidation and oxygen‐reduction reactions (ADTs=accelerated durability tests).
Hybrid perovskites such as MAPbI3 (MA = CH3NH3) exhibit a unique spin texture. The spin texture (as calculated within the Rashba model) has been suggested to be responsible for a suppression of ...radiative recombination due to a mismatch of spins at the band edges. Here we compute the spin texture from first principles and demonstrate that it does not suppress recombination. The exact spin texture is dominated by the inversion asymmetry of the local electrostatic potential, which is determined by the structural distortion induced by the MA molecule. In addition, the rotation of the MA molecule at room temperature leads to a dynamic spin texture in MAPbI3. These insights call for a reconsideration of the scenario that radiative recombination is suppressed and provide an in-depth understanding of the origin of the spin texture in hybrid perovskites, which is crucial for designing spintronic devices.
The parabrachial nucleus (PBN) is one of the major targets of spinal projection neurons and plays important roles in pain. However, the architecture of the spinoparabrachial pathway underlying its ...functional role in nociceptive information processing remains elusive. Here, we report that the PBN directly relays nociceptive signals from the spinal cord to the intralaminar thalamic nuclei (ILN). We demonstrate that the spinal cord connects with the PBN in a bilateral manner and that the ipsilateral spinoparabrachial pathway is critical for nocifensive behavior. We identify Tacr1-expressing neurons as the major neuronal subtype in the PBN that receives direct spinal input and show that these neurons are critical for processing nociceptive information. Furthermore, PBN neurons receiving spinal input form functional monosynaptic excitatory connections with neurons in the ILN, but not the amygdala. Together, our results delineate the neural circuit underlying nocifensive behavior, providing crucial insight into the circuit mechanism underlying nociceptive information processing.
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•The ipsi- and contralateral spinoparabrachial pathways are functionally distinct•The ipsilateral spinoparabrachial pathway mediates nocifensive behavior•Tacr1+ neurons in the PBN represent the major target of spinal projection•The PBN relays nociceptive information to the ILN via glutamatergic synapses
Deng et al. demonstrate that the ipsilateral spinoparabrachial pathway mediates nocifensive behavior and identify that the Tacr1+ neurons in the parabrachial nucleus represent the major target of the spinal projection. The authors also reveal the major downstream pathway for processing nociceptive information.
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