Growth Of Methacrylate-based Perovskite And Less Lead Perovskite Single Crystals And Application Of Photodetectors

Organic-inorganic hybrid perovskite materials have been widely investigated in recent years,which have became the stars in the fields of photovoltaic and photoelectric devices due to their advantages of low cost,simple preparation process and excellent optoelectronic properties.However,due to the vast majority of perovskite materials used in solar cells and other optoelectronic devices are polycrystalline films,which have porse and surface defects as well as the intrinsic instability originating from exposed to water vapor and light.That greatly limits the perovskite based photoelectric device performance.In addition,the toxicity of lead also makes the application of perovskite materials facing with enormous challenges.In consideration of the existence of defects within the microcrystalline thin film,as well as lead and instability issues of perovskite material,therefore,we use single crystal to improve the stability of perovskite materials and look for new lead-less perovskite materials to reduce the usage of lead.The progress of this topic is as follows:(1)We investigated the effects of precursor concentration,crystal growth temperature and other factors on the growth of formamidium-based lead iodide(FAPbI3)perovskite crystals during inverse temperature reactive crystallization process.It has been found that high quality and impurity free FAPbI3 single crystal could be obtained as precursor solution concentration was 1.0 M and incubation temperature was 100?.After changing the growth solution several times,a large size of 20 mm black a phase FAPbI3 single crystal could be obtained.The TGA results show that the single crystal exhibits a significantly higher thermal stability than the film,no sign of decomposition at 300?.The absorption edge is broaded to 870 nm.The obtained crystal has an extremely small trap state density(as low as 4.4 x 1010 cm-3)and very high carrier mobility(as high as 51± 6 cm2 V-1 s-1).Diamond-wire sawing process has also been applied to obtain FAPbI3 wafers with thickness of only 600 ?m.We use the FAPbI3 wafer to fabricate photodetector and find it possesses good photo response and great stability.(2)The less-Pb perovskite single crystals have been prepared by doping the precursor solution for growing MAPbI3 single crystal with divalent ion or mixture of monovalent and trivalent ions.For the sample doped with different proportion of Zn2+,the XRD diffraction peaks' positions shift to low angle with the increase of doping ratio.It is suggested that Zn2+ don't replace the site of Pb2+ in the lattice site,but exist in perovskite lattice in the form of interstitial atoms.In addition,the doped crystals with square shape.The higher quality of crystal can be achieved from the precursor solution doped with 15%Ca2+.The photodetector fabricated with the Ca2+ dopede single crystal has acceptable light response.