Morphology And Interface Control To Prepare High-efficiency Perovskite Solar Cells

Organic-inorganic hybird perovskite solar cells are the solar cells using organic-inorganic hybrid halogenated perovskite materials（hereinafter referred to as perovskite materials）as the absorptive layer.Perovskite materials are excellent materials for solar cells with the advantages of suitable bandgap,good light absorption coefficient,long carrier diffusion length,long carrier lifetime and direct bandgap,which gives perovskite solar cells（PSCs）have great commercial application potential.PSCs are likely to replace silicon-based solar cells as the backbone of the competition between solar energy and traditional energy.So far,the highest photoelectric conversion efficiency of PSCs reported in published articles has reached 24.02%,comparable to that of silicon-based solar cells.However,,the high-efficiency device can only be realized by a few research groups due to the sensitivity of PSCs to the preparation conditions.Through the optimization of the device,they were intervened that the light absorption of the perovskite layer,the carrier transport of the perovskite layer,and the carrier extraction process of the device.Finally,PSCs with photoelectric conversion efficiency close to 23%is obtained.The main contents are as follows:1.The apparent properties of perovskite films are the basic conditions that affect the photoelectric conversion efficiency of PSCs.In this work,Chapter 3 first defines the apparent properties of perovskite films for high-efficiency PSCs.In Chapter 3,lead acetate was added to the precursor to change the crystallization kinetics of the one-step method preparation and thereby perovskite films with different apparent properties were obtained.This chapter finally concludes that PSCs with high PCE should have the perovskite film with high coverage,low roughness and high purity.2.In Chapter 4,the intervention of the carrier transport of the perovskite thin film is realized through the adjustment of the microstructure of the perovskite film,which affected the carrier transport dynamics of the perovskite solar cell and finally improved device performance.Under the guidance of Chapter 3,the two-step method with high coverage and low roughness of the prepared perovskite film was selected as the preparation method of the perovskite film,and a high-purity perovskite film was obtained by reducing the annealing temperature.Subsequently,perovskite films with different microstructures were obtained by repeated spin-coating of organic cation halogen salts(FA_0.9MA_0.1I in this work).The effects of the morphology of the perovskite film on the carrier transport and device performance were obtained by testing the morphology,film electrical properties and so on.Finally,it is concluded that a high-quality perovskite film should have large grain size and small density of grain boundaries with grains vertically aligned between the two electrodes.In this chapter,the PL test results of the perovskite thin film and the TPV test results of the device prove that the change in the microstructure of the perovskite film positively affects the carrier transport process,thus achieving device performance improvement.3.Chapter 5 conducts the process of carrier extraction in the device by the interfacial modification of the perovskite solar cell device,thereby affecting the carrier transmission dynamics in the PSCs and thus improving the performance of the device.In Chapter 5,an interface modification material cesium carbonate,which is widely used in organic optoelectronic devices,was used to modifiy the perovskite solar cell device.Its unique properties enable the modification of the perovskite/PCBM to interface and form dipoles to improve charge extraction capabilities in the device.By exploring the relationship between the charge extraction capabilities and their corresponding device performance,it is concluded that improving the charge extraction capabilities in devices can improve the photoelectric conversion efficiency of perovskite solar cells.4.Chapter 6 implements the perovskite layer light utilization with interface modification,thereby increasing the short-circuit current density of the device.In Chapter6,cesium carbonate was applied to the modification of SnO₂-based n-i-p type perovskite solar cells,and it was also used to modify the ITO/SnO₂ interface to achieve ultra-high-efficiency perovskite solar cells.Through in-depth analysis of the experimental data,combined with optical simulation of the perovskite solar cell devices,the contributions of optical and electrical parts in this device were distinguished.It is concluded that improving the light utilization of the perovskite layer through optical optimization can improve the photoelectric conversion efficiency of the device.These improvements are independent from the performance improvement caused by electrical enhancements.This work intervened in the light utilization process in the PSCs through interface modification,thereby realizing the improvement of device performance.In addition,this chapter has also achieved nearly 23%PCE through the joint intervention of carrier transport in the perovskite layer,carrier extraction in the device,and light utilization of the perovskite film during the operation of the perovskite solar cell.In this work,they were intervened that the carrier transport of the perovskite layer in the working process of the perovskite solar cell,the carrier extraction in the device,and the light utilization of the perovskite thin film.Through the intervention of these working processes,the photoelectric conversion efficiency of the device is improved.