The Investigation On Doping-assist Crystallization Of Perovskite Films And Performance Of Optoelectronic Devices

Organic-inorganic perovskites have shown excellent optoelectronic property and are widely used in fabricating high-performance perovskite solar cells and light-emitting diodes,which is meaningful in solving the problems of energy and environment.To obtain high-performance devices,it is necessary to prepare high-quality perovskite films.This dissertation focuses on the regulating effects of doping-assist crystallization on film morphology,crystal structure,phase distribution and crystal orientation of perovskite,and further investigate optical properties of perovskite films and optoelectrical performance of the perovskite-based devies.The main contents can be divided into four parts:（1）The PMMA was used as additive to modulate the crystallization and film morphology of FASnI₃ perovskite,which have demonstrated useful in improving open-voltage(V_oc)and stability.The C=O bonds in PMMA molecule act as electron-pair donor and can interact with FA⁺,indicating the crystallization process can be effectively modulated by PMMA,so the shapes and sizes of perovskite crystals can be changed.Meanwhile,the film coverage can be improved.The optimized film morphology contribute to reduced leak current,defects passivation and improved stability.This work indicates it is an effective way that using polymer additive to enhace the photovoltaic performance of tin-based perovskite.（2）Transition metal Mn ion doping method can induce the change of perovskites’crystal structure,which has been demonstrated useful in modulating optoelectrical properties and realizing high photoelectric conversion efficiency（PCE）over 20%.The incorporated Mn ions are proved to forming interstitial ions in the lattice.Mn doping can cause reduced crystal size,decreased surface roughness,enhanced short wave photo-absoption,increased carrier lifetime,and reduced defect density.Moreover,Mn doping can also induce spin-related physical process,including double exchange effect and enhanced spin-orbit coupling（SOC）effect.The existence of both Mn²⁺and Mn³⁺can contribute to the charge transport between two adjacent ions via double exchange effect.By a combination of linearly and circularly polarized photo-excitations,the effect of Mn doping on intrinsic spin-orbit coupling（SOC）is explicitly determined.More dark states are expected to be available for the photocurrent generation.This work provides more insight into the underlying reason on photovolataic performance improvement of transition metal ion doped perovskite.（3）MACl additive method has been demonstrated useful in phase modulation and crystal orientation control of quasi-2D PEA₂MA₂Pb₃I₁₀ perovskite film.Increased phase purity can be realized,because MACl additive can modulate crystallization process and promote intermediate phase formation.Film morphology,crystal structure and crystal orientation can be obviously moudulated by MACl.When the MACl concentration is 20mg/mL,the perovskite film shows enlarged crystal size and mixed crystal orientation.Furthermore,the effect of MACl doping on the polarization of lateral photoluminescence was investigated.This work indicates it is an effective way that using MACl additive to modulate crystallization process of quasi-2D perovskite.（4）The quasi-2D perovskite with mixed crystal orientation has been demonstrtated useful in preparing dual-functional devices,which show both light-emitting and photovoltaic performance.The optimal device shows power conversion efficiency（PCE）of 8.64%,and an open voltage(V_oc)of 1.183 V.Meanwhile,the optimal device exhibits good light-emitting performance with a maximum luminance(L_max)of 1598 cd/m²,and an external quantum efficiency（EQE）of 2.2%.Both enhancement of photovoltaic and light-emitting performance can be ascribed to decreased defects density and enlarged charge mobility.Besides,the polarization of lateral EL intensity indicates that changing crystal orientation can affect the orientation of transient dipole moment,which can further influence the outcoupling efficiency.This work helps to understand the effects of quasi-2d perovskite’s crystal orientation on photovoltaic and light-emitting process.