Spectral Characteristics Of Defects In Novel Optoelectronic Functional Materials

Crystal structures often contain various degrees of defects,making a perfectly flawless crystal structure impossible.These crystal defects have a significant impact on the properties of the crystal.Some of the defects can endow the crystal with unique properties,while other defects will have negative impacts on the crystals’performance by destroying their internal structure.Therefore,this article focuses on studying the nitrogen-vacancy（NV）center in diamond,and defects in perovskite solar cell films,analyzing their different impacts on material properties.The NV center in diamond has many unique advantages,such as stable luminescence,long coherence time,and zero-phonon line visibility at room temperature,making it a potentially powerful carrier of quantum systems.The optically detected magnetic resonance（ODMR）spectrum of the NV center has a valley at 2.87 GHz.which can be split by a magnetic field,making the NV center suitable for magnetic field sensing.In terms of information acquisition,rotational motion has received increasing attention,and various physical mechanisms have been used for rotation sensing.The Barnett phenomenon refers to the magnetic field generated by neutral paramagnetic or ferromagnetic materials during rotation.The NV center exhibits paramagnetic properties at room temperature,meets the conditions for producing the Barnett effect,and is also an excellent magnetic probe.Therefore,by detecting the ODMR signal of the rotating NV center,it is expected to observe and verify the Barnett effect,further reflecting the current rotation speed.Unlike the benefits of the NV color center defects in diamonds,defects present in the absorption layer of solar cells hinder the transport of charge carriers within the device,thereby significantly reducing the efficiency of solar cells.In this study,a new type of perovskite solar cell was developed by using daminozide（DA）as an interlayer and additive simultaneously.Series of materials were prepared and their time-resolved spectra were studied.Based on the ultrafast spectra,we investigated the carrier dynamics and the impact of defect passivation on the relaxation process inside perovskite materials.The results indicate that the defects in the interface and interior of perovskite significantly reduce the carrier transport,while the DA interlayer and passivator effectively passivate the defects,reducing the defect recombination effect on the carriers,thus exhibiting more suitable carrier transport dynamics.As a result,the performance of the perovskite solar cell was significantly improved.The main contents of this paper are as follows:1.High-concentration NV center samples were prepared by electron irradiation and high-temperature annealing.An experimental design was created to generate concentric rings of current by rotating charged disk,with a metal cylinder in an electric field and a charged super capacitor serving as the charged disk,and the magnetic field generated by its rotation was calculated.2.Using NV centers as magnetic probes,the Barnett field produced by the rotation of superparamagnetic Fe₃O₄nanoparticles was studied,but no changes in the ODMR spectra due to rotation were observed.The ODMR signals of diamond NV center samples were detected at different rotation speeds with and without an external magnetic field.Finally,the ODMR spectra of a diamond with<110>orientation rich in nitrogen impurities were detected at different rotation speeds.There was some broadening observed in the spectra,which represented a preliminary observation of the Barnett field.3.Two series of six different perovskite solar cell samples were prepared and characterized using transient absorption techniques to investigate their dynamic.By comparing the results of ultrafast spectroscopy,the relaxation processes of charge carriers inside the perovskite materials were analyzed,and it was found that defects significantly affect carrier transport.The introduction of DA effectively reduced defects at the interface and inside of perovskite films,improving the optoelectronic properties of the device,resulting in better device performance.This conclusion provides theoretical guidance for the passivation of defects in solar cells and the preparation of high-performance perovskite solar cells.