| Halide perovskites have shown huge potential in the field of optoelectronic applications,due to their outstanding intrinsic optoelectronic properties,such as large light absorption coefficient,long carrier lifetime,well-balanced electron hole mobility and high luminescence quantum efficiency.However,it is extremely difficult to endow them with luminesce at wavelengths longer than 1.0 ?m,because of the inherent limitation of their band gaps,thus greatly limiting their applications in telecommunications.Besides,the lead toxicity in lead-based halide perovskites poses health risks to human beings and significant danger to the ecosystem,which has been an urgent problem.In view of this,we demonstrated that metal-doped and alloyed can be efficiently used to modulate the intrinsic optoelectronic properties in halide perovskites,thereby broadening device applications and improving the performance of halide perovskite-based devices.Overall,our work can be summarized into four categories as below.1.We have successfully synthesized the Bi-doped CsPbI3 powders by solid phase method and further investigated its photophysical properties.It was found that Bi-doped CsPbI3 has novel ultrabroad near infrared(NIR)photoluminescence(PL).Based on our experiment results,we found that the observed NIR PL from Bi-doped CsPbI3 is not connected with single-ion Bi active centers,but with structural defects induced by Bi3+.This can be explained according to our newly proposed model known as "polaronic defects".In addition,we also demonstrated that the growth of luminescent Bi-doped CsPbI3 nanowires and nanocrystals with ultrabroad NIR PL can be achieved by using a simple liquid phase solution method,which might provide a new approach to adjust optoelectronic properties of other halide perovskites2.Bi-doped CH3NH3PbI3 polycrystalline films were prepared by solution-processing and their optical properties were further investigated.Compared to the pristine one,the ultrabroad NIR PL that covered whole telecommunication windows were observed in Bi-doped samples.In addition,we confirmed that the observed NIR PL originates from one class of Bi-doping-induced optically active center,which is considered to be connected with distorted[PbI6]units coupled with spatially localized bipolarons.Finally,we accomplished the electroluminescence at telecommunication windows by using Bi-doped CH3NH3PbI3 as an emissive layer,marking the first electrically driven devices using Bi-doped halide perovskites.3.We demonstrated that the fabrication of smooth,high-quality Bi-activated CH3NH3PbI3 can be prepared by optimizing the types of precursors and its molar ratio in the synthesis process,and without influencing on the NIR PL properties.By utilizing the characterization measurements such as photothermal deflection spectroscopy to further analyze the photophysical properties of the material,we can directly prove that the NIR PL originates from the structure defects induced by Bi doping.Furthermore,we achieved optical amplification in the whole telecommunication window by using Bi-activated CH3NH3PbI3 as gain medium,which represents the first work on the attainment of such a performance among halide perovskites.4.We synthesized pinhole-free,high-quality all-inorganic Pb-Sn alloyed halide perovskite thin films through low-temperature solution-processing,and fabricated solar cells based on the Pb-Sn alloyed perovskite films.The bandgap positions of alloyed perovskites can be easily adjusted by changing Sn contents.Therefore,the modified material can absorb light in a wider wavelength range,thereby improving the efficiency of sunlight utilization.Finally,we fabricated solar cells that used Pb-Sn alloyed perovskite as the light absorbing layer exhibit a high efficiency of 7.3%,showing high reproducibility and hysteresis-free performance,which has a positive effect on the low-cost,low toxicity and high efficiency solar cells. |
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