Principle Of Optical Management And Its Application In Polymer-Based Inverted Perovskite Solar Cells

Organic-inorganic hybrid perovskite materials are the first type of optoelectronic materials with extremely high light absorption coefficient,ideal and adjustable forbidden band width.It only needs a few hundred nanometers to fully absorb light.At the same time,its carrier mobility is high,its diffusion length is long,and its tolerance to impurities is much higher than a series of excellent semiconductor materials.In the development of solar cells with perovskite materials as the absorption layer in about ten years,the photoelectric conversion efficiency obtained in laboratory has boosted from 3.8%to more than 25%.Perovskite solar cells with sandwiched stacks as the basic structure have become one of the superstar that have attracted worldwide attention this century.At present,the upright structure based on the metal oxide?TiO₂,SnO₂?electron-transport layer as a substrate requires complex annealing processes,requires high-temperature annealing,oxygen doping,cannot be used for flexible devices,and has device hysteresis and poor UV stability.Factors affecting the industrialization of the upright structure will face huge challenges.In contrast,the inverted structure based on the conductive polymer?PEDOT:PSS,PTAA?hole transport layer satisfies the advantages of simple preparation,no doping,and can be used for flexible devices without inherent disadvantages such as hysteresis.It is an ideal structure for industrialization.However,the laboratory photoelectric conversion efficiency of inverted devices is relatively low.According to the reports,in the perovskite absorption layer obtained by the same preparation process,the open-circuit voltage and fill factor of the final device are basically the same,but the short-circuit currents are quite different.Based on the working principle of perovskite solar cell devices,the short-circuit current is affected by light absorption,carrier transport and recombination,and incident light loss as well.Studies have shown that solar cells,as the device for photoelectric conversion,are susceptible to interference in the film because they have a typical sandwiched structure and the thickness of each layer is at the nanometer level.Therefore,the incident light loss is one of the main ways of energy loss for perovskite solar cells.This thesis mainly uses PEDOT:PSS and PTAA as two kinds of conductive polymer hole transport layers at light incident side to investigate the energy loss of polymer-based inverted perovskite solar cells,and to find out corresponding solutions.The research content includes the following three aspects:1.Establish a model based on the transmission matrix and test data and perform feed-back correction to explore the theory of optical management.In this study,a basic cycle from experiments to optical simulations and guided experiments is introduced,which mainly addresses the current methods and then theories of optical management of polymer-based inverted perovskite sells.In the experiment,on the one hand,the optical model of each material was used to establish a basic model;on the other hand,a series of polymer-based perovskite solar cells with high conversion efficiency were successfully prepared through repeated experiments.The model was corrected multiple times according to the criteria of the one-to-one correspondence between the experimental results and the peak values of the simulation results.The corrected model is used to carry out simulation explorations in various aspects,such as interference in various layers,multiple interface microstructures to enhance the light capture capability of the cells.The calculation results show that the thickness of the polymer film layer will cause interference to a great extent.The thinner the polymer layer,the more favorable the perovskite absorption;the change in the microstructure of the polymer/perovskite interface will alter the perovskite absorption.Significant transmittance improvement,up to 95%of the incident light is possible.2.Self-assembled single-layer polymers reduce light interference in perovskite solar cells.According to one of the simulation calculations,the thinner the polymer layer,the stronger the perovskite absorption.We self-assembled PEDOT:PSS polymer on the surface of ITO for the first time,and successfully prepared a single-layer PEDOT:PSS film with full coverage and uniform thickness.The experimentally measured EQE of the devices correspond to the optical simulation results,demonstrating the optical performance of the self-assembled single-layer PEDOT:PSS film.The excellent optical and electrical performance of the single-layer PEDOT:PSS film were demonstrated.Finally,we increased the efficiency from 15.64%to 18.91%and the V_OC to 1.13 V.It is proved that the self-assembly process is an effective method to reduce the thickness of PEDOT:PSS films and form a stable interface.3.Polymer textures coordinate optical structure matching in perovskite solar cells.According to one of the simulation calculations,the change in the microstructure of the polymer/perovskite interface will significantly increase light absorption in perovskite.In this section,we mainly introduces the polymer texture interface design inside the perovskite devices and successfully applied in the high efficiency inverted perovskite solar cells.This texture structure is used for the first time in inverted perovskite solar cells,which is directly at the light-entering side of perovskite.UV-Vis results show that the absorption of the device is significantly enhanced.PL,TRPL,TPV/TPC and other results show that the contribution of charge extraction can be ignored.It is successfully demonstrated experimentally that the texture interface improves the light capture ability of the perovskite solar cells,and finally improves the solar cell efficiency from 18.3%to21.6%,the highest one of inverted perovskite solar cells.