Cesium lead halide perovskite triangular nanorods as high-gain medium and effective cavities for multiphoton- pumped lasing

High-performance multiphoton-pumped lasers based on cesium lead halide perovskite nanostructures are promising for nonlinear optics and practical frequency upconversion devices in integrated photonics. However, the performance of such lasers is highly dependent on the quality of the material and cavity, which makes their fabrication challenging. Herein, we demonstrate that cesium lead halide perovskite triangular nanorods fabricated via vapor methods can serve as gain media and effective cavities for multiphoton-pumped lasers. We observed blue-shifts of the lasing modes in the excitation fluence-dependent lasing spectra at increased excitation powers, which fits well with the dynamics of Burstein-Moss shifts caused by the band filling effect. Moreover, efficient multiphoton lasing in CsPbBr3 nanorods can be realized in a wide excitation wavelength range （700-1,400 nm）. The dynamics of multiphoton lasing were investigated by time-resolved photoluminescence spectroscopy, which indicated that an electron-hole plasma is responsible for the multiphoton-pumped lasing. This work could lead to new opportunities and applications for cesium lead halide perovskite nanostructures in frequency upconversion lasing devices and optical interconnect systems.

Long-lasting photoluminescence quantum yield of cesium lead halide perovskite-type quantum dots

Cesium lead halide perovskite(CsPbX_(3),X=Cl,Br,I)quantum dots(QDs)and their partly Mn^(2+)-substituted QDs(CsPb1–xMnxX3)attract considerable attention owing to their unique photoluminescence(PL)efficiencies.The two types of QDs,having different PL decay dynamics,needed to be further investigated in a form of aggregates to understand their solid-state-induced exciton dynamics in conjunction with their behaviors upon degradation to achieve practical applications of those promising QDs.However,thus far,these QDs have not been sufficiently investigated to obtain deep insights related to the long-term stability of their PL properties as aggregated solid-states.Therefore,in this study,we comparatively examined CsPbX_(3)-and CsPb1–xMnxX_(3)-type QDs stocked for>50 d under dark ambient conditions by using excitation wavelength-dependent PL quantum yield and time-resolved PL spectroscopy.These investigations were performed with powder samples in addition to solutions to determine the influence of the inter-QD interaction of the aged QD aggregates on their radiative decays.It turns out that the Mn^(2+)-substituted QDs exhibited long-lasting PL quantum efficiencies,while the unsubstituted CsPbX_(3)-type QDs exhibited a drastic reduction of their PL efficiencies.And the obtained PL traces were clearly sensitive to the sample status.This is discussed with the possible interaction depending on the size and distance of the QD aggregates.

Effectively Inhibit Phase Separation to Improve Efficiency and Stability of All-Inorganic Planar CsPbIBr2 Perovskite Solar Cells

The advancement in a power conversion efficiency(PCE)to reach 25%,the inorganic perovskites are being explored intensively as promising optoelectronic materials due to their excellent photovoltaic performance,i.e.,thermal stability and efficiency.Lately,the inorganic cesium lead halide perovskite is studied to show enhanced light absorption,however,it suffers from the phase separate into I-rich and Br-rich phase which leads to poor film quality due to difference of electronegativity.Herein,we propose a unique solution of controlling the rate of solvent volatilization followed by gel method to inhibit phase separation effectively to obtain the homogenous and pinhole-free CsPbIBr2 films with high crystalline quality.In this study,an inverted planar device based on a light absorber of CsPbIBr2 is prepared to achieve a power conversion efficiency of 8.8%(maintain a stabilized value of 8%in ambient air conditions).Surprisingly,the optimized cell without encapsulation shows excellent long-term stability,as it maintained 90%initial efficiency over 500 h and controlled storage at around 45%relative humidity and 25℃.

Antimony doped CsPbI_(2)Br for high-stability all-inorganic perovskite solar cells

All-inorganic perovskites,adopting cesium(Cs+)cation to completely replace the organic component of A-sites of hybrid organic–inorganic halide perovskites,have attracted much attention owing to the excellent thermal stability.However,all-inorganic iodine-based perovskites generally exhibit poor phase stability in ambient conditions.Herein,we propose an efficient strategy to introduce antimony(Sb^(3+))into the crystalline lattices of CsPbI_(2)Br perovskite,which can effectively regulate the growth of perovskite crystals to obtain a more stable perovskite phase.Due to the much smaller ionic radius and lower electronegativity of trivalent Sb^(3+)than those of Pb^(2+),the Sb^(3+)doping can decrease surface defects and suppress charge recombination,resulting in longer carrier lifetime and negligible hysteresis.As a result,the all-inorganic perovskite solar cells(PSCs)based on 0.25%Sb^(3+)doped CsPbI_(2)Br light absorber and screen-printable nanocarbon counter electrode achieved a power conversion efficiency of 11.06%,which is 16%higher than that of the control devices without Sb^(3+)doping.Moreover,the Sb^(3+)doped all-inorganic PSCs also exhibited greatly improved endurance against heat and moisture.Due to the use of low-cost and easy-to-process nanocarbon counter electrodes,the manufacturing process of the all-inorganic PSCs is very convenient and highly repeatable,and the manufacturing cost can be greatly reduced.This work offers a promising approach to constructing high-stability all-inorganic PSCs by introducing appropriate lattice doping.

CH_(3)I sensing using yttrium single atom-doped perovskite nanocrystals

Nanocrystals(NCs)of cesium lead halide perovskites are optically unstable,which prevents their use in optical sensors.The combination of perovskite NCs and metal single atoms(SAs)may be a good solution to this issue.Unfortunately,depositing metal SAs on perovskite NCs remains a challenge due to relative weak metal-halide bonds.Herein,we present that,via a photo assisted method using cesium lead halide perovskite NCs as host material to anchor Y single atoms,we successfully synthesize Y SA anchored CsPbBr_(3)NCs(Y-SA/CsPbBr_(3)NCs)with outstanding fluorescence stability through the formation of two Y-O bonds and two Y-Br bonds.In comparison to bare CsPbBr_(3)NCs,Y-SA/CsPbBr_(3)NCs possess more stable optical characteristics.The as-synthesized Y-SA/CsPbBr_(3)NCs can be employed as a colorimetric platform to perform rapid CH_(3)I sensing.Detection limit of 0.044 ppm is exhibited in this approach with excellent anti-interference performance.The YSA/CsPbBr_(3)NCs-based system has been applied to the detection of CH_(3)I in sweet potato samples with satisfying results.

Oriented inorganic perovskite absorbers processed by colloidal-phase fumigation

Inorganic perovskite absorbers are promising candidates for next-generation photovoltaics due to their good thermal and light stabilities.Halide-mixed Cs Pb I_(x)Br_(3-x)reach a compromise between its structural tolerance and absorption edge,yet the power conversion efficiencies(PCEs)of the asfabricated cells can be considerably limited by the nonideal quality of solution-processed films.Here we demonstrated a fumigation strategy on colloidal perovskite films using dualO-donor ethyl acetate(EA).By in-situ monitoring this stage with grazing-incidence wide-angle X-ray scattering technology,we reveal that EA fumigation would impose ripening barrier on colloidal inorganic perovskites and hence slow down the nucleation rate,leading to an intermediate state for processing high-crystallinity and oriented perovskite films with improved photophysical properties.An optimized PCE of 16.6%was finally yielded upon wide-bandgap(1.9 eV)perovskite absorber.

CsPb(I_(x)Br_(1-x))_(3) solar cells

Owing to its nice performance, low cost, and simple solution-processing, organic-inorganic hybrid perovskite solar cell(PSC) becomes a promising candidate for next-generation high-efficiency solar cells.The power conversion efficiency(PCE) has boosted from 3.8% to 25.2% over the past ten years. Despite the rapid progress in PCE, the device stability is a key issue that impedes the commercialization of PSCs. Recently, all-inorganic cesium lead halide perovskites have attracted much attention due to their better stability compared with their organic-inorganic counterpart. In this progress report, we summarize the properties of CsPb(IxBr1-x)3 and their applications in solar cells. The current challenges and corresponding solutions are discussed. Finally, we share our perspectives on CsPb(IxBr1-x)3 solar cells and outline possible directions to further improve the device performance.