Preparation of lead halide perovskite with high photoluminescence quantum efficiency

Since its discovery in 1958, lead halide perovskite (cspbx 3) has attracted the attention of many scholars because of its excellent optical and electrical properties This material has a large absorption coefficient, a long electron transport path, and its band gap can be adjusted by changing the type of halogen in its structure to emit different colors of light These characteristics make them have great application prospects in the fields of solar cell, led, laser and photodetector But for a long time, the photoluminescence quantum efficiency (plqy) of only red emitting cspbi 3 is close to 100%, and the plqy of csppbbr 3 is generally between 60% and 80%, but the plqy of cspbcl 3 with higher emission energy is less than 10% Although the researchers can improve their luminescent properties to some extent by doping and other means, they are still not ideal for cspbcl3 Figure 1 Lead halide perovskite nanocrystals prepared by a new method (picture source: angel Chem Int ed.) Recently, sujoy baitalik and Narayan Pradhan of Indian Association for the popularization of science jointly reported a synthesis method of perovskite nanocrystals Three kinds of lead halide perovskite materials (cspbi 3, csppbbr 3 and cspbcl) were prepared by this method 3) All of them have very high quantum efficiency of photoluminescence This achievement was published in "near unityphotoluminescence quantum efficiency for all cspbx 3 (x = Cl, Br andI) perovskite nanocrystals: a generic synthesis approach" in German Applied Chemistry (DOI: 10.1002 / anie 201900374) Considering the existing problems in the preparation of perovskite, the author redesigned the reaction steps Firstly, CS 2CO 3 and PbO 2 were mixed in the ratio of 1:2 After heating the mixture to a certain temperature, the oleic acid ammonium halide (ola-hx) was added to the system By this method, the proportion of CS, Pb and halogen in the system is strictly controlled, so that the system contains neither too much Pb nor too little halogen After obtaining three kinds of lead halide perovskite nanocrystals, the author has studied their luminescent properties The results show that their spectral shapes are consistent with the perovskite nanocrystals reported before, but the plqy of three kinds of perovskite nanocrystals including cspbcl3 is more than 90% Fig 2 UV and fluorescence spectra of three perovskite nanomaterials (picture source: angelw Chem Int ed.) high quantum efficiency cspbi 3 preparation method has been common, so it is not representative Therefore, the author studied the structure of cspbcl3 and csppbbr 3 in detail The results of powder X-ray diffraction (PXRD) show that both cspbcl 3 and csppbbr 3 have cubic phase TEM results show that the two kinds of nanocrystals are cubic, in which the diameter of cspbcl3 is about 12 nm, while that of csppbbr 3 is about 15 nm Fig 3 PXRD and TEM patterns of cspbcl3 and csppbbr 3 (picture source: angel Chem Int ed.) after determining that perovskite materials with excellent luminous efficiency can be obtained by this method, the author also studied the effect of different reaction conditions on perovskite plqy First of all, the author changed the ratio of CS and Pb, and found that for PBR perovskite, although the perovskite obtained at the ratio of 1:1 has the highest plqy, the difference is not significant, while the change of the ratio of CS and Pb has a very obvious effect on PBR perovskite In addition, the higher the temperature, the higher the plqy of perovskite Highlights: the author developed a synthesis method of perovskite nanocrystals The three lead halide perovskites prepared by this method have high photoluminescence quantum efficiency Full text author: anirban Dutta, Rakesh Kumar behera, poulami pal, sujoy baitalik, and Narayan Pradhan.