Investigation On Light Management In Perovskite Solar Cells And Process Conditions Of Inverted CsPbI₃ Solar Cells

Perovskite materials have attracted much attention due to their excellent optoelectronic properties and perovskite-related solar cells are also popular research topics in recent years.Generally,perovskite solar cells do not require special light management due to their high absorption coefficient.However,rational light management is vital to enhance the performance of the cells when applied in flexible solar cells and tandem solar cells（TSCs）.In flexible perovskite solar cells,in order to obtain good mechanical flexibility,perovskite films usually need to be thinned,which will reduce their light absorption capacity and require reasonable light management to improve light absorption.In the perovskite/c-Si two-terminal TSCs which possess much more complex structures,excellent light management is the key to further improving the efficiency.In this thesis,a series of light management studies are carried out for ultrathin flexible perovskite solar cells and a promising mass production CsPbI₃/TOPCon（Tunnel Oxide Passivated Contact solar cell）TSCs from the perspective of simulation.In the experiment,the preparation technology of inverted CsPbI₃ perovskite solar cells was explored.The main achievements are as follows:（1）The optical simulation of ultrathin flexible perovskite solar cells is carried out by using the finite time domain difference method.The optical properties and omnidirectionality of ultrathin flexible perovskite solar cells with different light trapping mechanisms are studied.By introducing three light trapping mechanisms,a namely antireflection layer,texture,and surface plasmon,after optimizing their structural parameters,the photogenerated current density of ultrathin flexible perovskite solar cells has been improved to a certain extent and the improvement of texture structure is the most significant.Meanwhile,by studying the dependence of the flexible perovskite cells performance on different light trapping mechanisms respectively and the angle of the incident light,we find that the photogenerated current density demonstrates a quasi-omnidirectional tendency in the angle range of 0～50°,which can maintain close to the value of the normal incidences.（2）A CsPbI₃/TOPCon TSC with high stability,low cost,and high-temperature resistance is proposed.The optical performance optimization scheme is systematically investigated for this TSC.The optical properties of CsPbI₃/TOPCon TSCs were simulated by a combination of ray tracing and transfer matrix methods.The light management of CsPbI₃/TOPCon TSCs begins with the optimization of the surface texture of the Si sub-cell,pointing out that the bifacial inverted pyramid structure with a small rear-side angle can sharply reduce the reflection.The current matching between the sub-cells is discussed by adjusting the thicknesses of the CsPbI₃ layer and the Si layer.The optimization direction of the front-side transparent conductive oxide（TCO）is pointed out after comparing the parasitic absorption of various TCOs.Finally,a CsPbI₃/TOPCon tandem solar cell structure with a conversion efficiency of 32.11%is proposed after effective light management,which provides a practical guide for obtaining high-efficiency perovskite/silicon TSCs.（3）The effects of annealing conditions on the performance of CsPbI₃ films and inverted CsPbI₃ perovskite solar cells were investigated.By optimizing the annealing conditions,a three-step ladder annealing technique was developed.Compared with the conventional two-step annealing technique,the obtained CsPbI₃ films have better humidity stability and lower defect state density.Finally,the average efficiency of the obtained FTO（F-doped Tin Oxide）/Ni O_x/CsPbI₃/OAI（n-Octylammonium Iodide）/C₆₀/BCP（Bathocuproine）/Ag inverted CsPbI₃ solar cells reach 13.11%,higher than the value of 12.27%for the counterparts without pre-annealing.Stability tests showed that the device maintained 80%of its initial efficiency after 25 days in a nitrogen-filled glovebox.This work provides a basis for the application of inverted CsPbI₃ solar cells in CsPbI₃/TOPCon TSCs.