Hybrid perovskites have attracted considerable attention due to their excellent optoelectronic properties and facile processing. Beyond their wide usage in various energy‐related devices and optoelectronic applications, in particular photovoltaic cells, these materials have also been employed as active candidates in field‐effect transistors (FETs). However, the low stability of these materials is still a substantial challenge for their applications and commercialization. Low‐dimensional (two‐ or quasi‐two‐) perovskites, which are formed by introducing larger organic amine groups into the perovskite structure, not only offer great potential for the development of high stability devices, but also achieve higher field‐effect mobility due to the low ion migrations at room temperature. To date, the emerging low‐dimensional perovskite FETs have already gained unprecedented developments. This review mainly summarizes and evaluates the recent progress on low‐dimensional perovskite FETs and proposes solutions for the possible challenges. First, along with the detailed comparisons, the advantages of low‐dimensional perovskites that can overcome the demerits of conventional 3D perovskites for FETs are presented in detail. Thereafter, the achievements and development of low‐dimensional perovskite‐based FETs are briefly reviewed, followed by the discussion of field‐effect mobility and other challenges and opportunities of low‐dimensional perovskites for FETs. Finally, a summary and outlook are given.

All-inorganic lead-free CsSnBr3 is attractive for applications in solar cells due to its nontoxicity and stability, but the device performance to date has been poor. Besides the intrinsic properties, impurities induced from electrodes may significantly influence the device performance. Here, we systematically studied the stability, transition energy levels, and diffusion of impurities from the most commonly used electrodes (Au, Ag, Cu, graphite, and graphene) in CsSnBr3 based on density functional theory calculations. Our results reveal that, whereas graphite and graphene electrodes exhibit negligible influence on CsSnBr3 due to the relatively high formation energies for carbon impurities in CsSnBr3, atoms from the metal electrodes can effectively diffuse into CsSnBr3 along interstice and form electrically active impurities in CsSnBr3. In this case, a significant amount of donor interstitial impurities, such as $$Ag_i^ +$$ A g i + , $$Cu_i^ +$$ C u i + , and $$Au_i^ +$$ A u i + , will be formed under p-type conditions, whereas the Sn-site substitutional acceptor impurities, namely $$Au_{Sn}^{2 - }$$ A u S n 2 − , $$Ag_{Sn}^{2 - }$$ A g S n 2 − , and $$Cu_{Sn}^{2 - }$$ C u S n 2 − , are the dominant impurities, especially under n-type conditions. In particular, except for $$Au_i^ +$$ A u i + , all these major impurities from the metal electrodes act as nonradiative recombination centers in CsSnBr3 and significantly degrade the device performance. Our work highlights the distinct behaviors of the electrode impurities in CsSnBr3 and their influence on the related devices and provides valuable information for identifying suitable electrodes for optoelectronic applications.

Metal selenides have attracted significant attention as practically promising anode materials in alkali metal-ion batteries because of their high theoretical capacity. However, a drawback is that these do not provide sufficient rate performance and cycle stability for large-scale. Here, anion defect-tuned ultranarrow bandgap bimetallic selenide nanoparticles anchored on honeycomblike N-doped, porous carbon dominated by pyrrolic nitrogen is reported. This targeted defect chemistry and unique structure facilitate rapid diffusion of lithium-potassium ions to provide increased pseudo-capacitance that boosts electrochemical performance. It is demonstrated that in lithiumand potassium-ion batteries (LIB and KIB), the composite exhibits high specific capacity, and excellent cycle stability with a reversible capacity of 937 mA h g −1 at 2 A g −1 for LIB and 304 mA h g −1 at 1 A g −1 for KIB following 1000 cycles, together with superior rate capability of, respectively, 499 mA h g -1 for LIB and 139 mA h g -1 for KIB at 10 A g -1 . A synergistic effect of the greater lithium/potassium ion adsorption energy of the bimetallic selenide and N-doped carbon boosts ion diffusion kinetics of the materials is confirmed. It is concluded that, these findings will be of immediate benefit to the practical development of alkali-metal ion batteries.

Hydrogen interstitials are expected to be important in organic–inorganic hybrid perovskites; however, the characteristics and behaviors of hydrogen in perovskites remain poorly understood. Here, on the basis of density functional theory calculations, we quantitatively reported that both atomic and molecular hydrogen interstitials can form in hybrid MAPbI3 and MASnI3 perovskites. Whereas molecular hydrogen interstitial, H2, is chemically inert, atomic hydrogen interstitial, H i , serves as an electrically active negative-U defect. We identify high-density H i + as a significant origin of ionic conductivity in p-type MAPbI3 under the hydrogen-rich conditions, with the calculated activation energy being comparable to that measured in experiments. The highly diffusive H i + ions are expected to impact hysteresis, charge separation, device polarization, and photogenerated field-screening effect and consequently degrade the solar cell performance. We evaluated approaches for mitigating such detrimental effects and suggested that synthesizing the perovskites with slightly extra iodine addition or tin alloying can effectively suppress the concentration of H i +. Our results are important to understand the fundamental aspects of hydrogen in perovskites in general and offer valuable insight for further improving the performance of perovskite solar cells and other optoelectronic devices via defect engineering.

Identification and passivation of defect-induced electron–hole recombination centers are currently crucial for improving the efficiency of hybrid perovskite solar cells. Besides general intrinsic defects, experimental reports have indicated that hydrogen interstitials are also abundant in hybrid perovskite layers; however, few reports have evaluated the effect of such defects on the charge carrier recombination and device efficiencies. Here, we reveal that under I-poor synthesis conditions, the negatively charged monatomic hydrogen interstitial, H i –, will form in the prototypical CH3NH3PbI3 perovskite layer, acting as a detrimental deep-level defect, which leads to efficient electron–hole recombination and lowers the cell performance. We further rationalize that Br doping can mitigate the large atomic displacement caused by the presence of H i – and hence suppress the formation of the deep localized state. The results advance the knowledge of the deep-level defects in hybrid perovskites and provide useful information for enhancing solar cell performance by defect engineering.