Research On Improving The Performance And Stability Of Perovskite Solar Cells

In recent years,perovskite solar cells(PSCs)have developed rapidly due to their excellent photovoltaic performance.The power conversion efficiency of currently certified PSCs has reached 25.5%,which is comparable to commercial silicon-based cells.In PSCs,the selection and preparation of the carrier transport layer and the perovskite active layer,as well as the regulation of the carrier transport layer/perovskite interface characteristics have a decisive influence on the performance of the device.The transport layer not only plays a role in extracting and transporting photogenerated carriers,but also affects the nucleation and crystallization of the perovskite absorption layer.The quality of the perovskite absorber layer is a key factor that determines the performance and stability of the device.This paper used lead-halide compounds as the PSCs absorption layer,focusing on the analysis of the influence of the carrier transport film,the carrier transport film/perovskite interface and the crystal quality and defects of the perovskite film on the device performance.The influence of the material structure of each layer and the interface on the device performance is studied in detail.The main research contents are as follows:(1)Firstly,the dual electron transport layer of amorphous Zn₂SnO₄(am-ZTO) and SnO₂ is successfully introduced into the PSCs.The am-ZTO film prepared by laser pulse deposition technology has a denser and flatter structure.Therefore,the leakage current formed by the direct contact between the absorber film and FTO layer is reduced.Moreover,a suitable energy level structure of two films constructs a gradient carrier transmission channel,which improves the carrier transmission effect.Under the dual regulation,the power convension efficiency of the device had increased from 17.8%to 20.04%.The stability of the modified PSCs has been obviously increased.The efficiency of the PSCs can still keep 90%of its original efficiency stored under ambient condition without any encapsulation for 210 h.This work provides a strategy to design and selection of electron transport layer.(2)Secondly,thiourea and iodide ions(ITU)were added into PSCs to increase the performance of absorber film.The modification of ITU can not only increase the grain size of the film,but also passivate the iodide ion defects caused by uncoordinated Pb atoms.Based on high-quality films,the power conversion efficiency of PSCs has increased from 17.75%to 20.39%.At the same time,the devices can retain 80%of the initial conversion efficiency after 30 days of aging in ambient atmosphere.This work is of great significance for the study of adjusting the crystal quality of the absorption layer to improve the photoelectric conversion efficiency and stability of the device.(3)Thirdly,adding CsPbBr₃ nanocrystals into the PSCs can well increase the performance of the perovskite layer and also improve the interface properties between the absorber layer and hole transport layer.CsPbBr₃ perovskite nanocrystals are used to control the growth of perovskite layer to obtain lage grain size and low defect state.Moreover,a Cs_1-yMA_yPbI_3-xBr_x layer with gradient energy level transfer is constructed on the surface of the absorber layer,promoting the energy level between the perovskite and Spiro-OMe TAD smaller.The collection efficiency of hole carriers is improved.Under the dual regulation,the power conversion efficiency of the device had increased from 18.51%to 20.46%.This work has certain reference significance for improving the performance of the device by adjusting the crystal quality of the absorption layer and the interface between the absorption layer and the transmission layer.(4)Finally,three different non-fullerene organic semiconductors with different terminal groups are introduced into the PSCs,which controlled the quality of the perovskite films and bidirectional interface between the perovskite films and the upper and lower transmission layers.Non-fullerene organic semiconductors with specific groups are introduced into the perovskite film,which improves the crystalline quality of the perovskite film and improveds the energy level matching between the transmission layer and the absorption layer.In addition,the perovskite film passivated by BTP-4F has the best energy level between the transport layers of PSCs.This can increase the carrier extraction performance.Under various adjustments,the optimal power conversion efficiency of the device after BTP-4F passivation reached 22.16%,and the device can maintain nearly 86%of its initial efficiency after 5000 hours of storage at room temperature.After heating in air at 100? for 30 hours,it can maintain about 72%of its initial performance.This work provides an effective method for realizing devices with high efficiency,high long-term stability and high thermal stability.