Study On The Fabrication Of High-Efficiency Perovskite Solar Cells And Large-area Devices

Energy is the foundation of human social development and the core of competition among countries around the world.Although traditional fossil fuels play an important role in human production and life,their reserves are limited and can cause environmental problems.Therefore,actively addressing the severe energy challenges and ensuring sustainable development of human society has become an important issue facing all countries today.As a responsible major country,China has put forward the goals of"carbon peak"and"carbon neutrality",and actively developed renewable energy.Solar energy,due to its stable source,wide distribution,and pollution-free advantages,has attracted widespread attention and become a popular choice in renewable energy.A solar cell is a device that converts solar energy into electrical energy.However,the mainstream crystalline silicon solar cells on the market currently face the dilemma of difficult efficiency improvement and high cost,which limits the further development of the photovoltaic industry.Perovskite solar cells（PSCs）,as a new type of photovoltaic cell,have the advantages of high efficiency,easy preparation,and low cost.Currently,their highest certified power conversion efficiency（PCE）has reached 26.0%,equivalent to that of crystalline silicon solar cells,and has therefore received extensive attention.Currently,the development of PSCs still faces multiple challenges.Firstly,the perovskite light-absorbing layer is the core functional layer in PSCs.Its quality is one of the important factors affecting the performance and stability of PSCs.The presence of defects caused by poor quality films can significantly reduce the efficiency and stability of PSCs.Secondly,how to improve the extraction and transport efficiency of photo-generated charge carriers at the interface between the perovskite and adjacent charge transport layers is also a key challenge.In PSCs,charge carriers need to be extracted and transported through the interface,but this process can easily produce non-radiative recombination and back-flow losses,which degrade device performance.In addition,the fabrication process of large-area devices also needs to be further optimized to ensure production stability and reproducibility.Finally,the long-term storage stability of PSCs remains a challenge,with PSCs experiencing performance degradation or even failure in environments with high temperatures,humidity and prolonged exposure to light.To address these issues,in this study,the author proposed new ideas and strategies such as perovskite crystal film growth regulation,interface engineering,and optimization of preparation processes,aiming to improve the performance of PSCs and prepare high-efficiency large-area perovskite solar modules（PSMs）.The details are as follows:（1）Regulate the perovskite crystal film growth and interface modificationUsing the typical all-inorganic perovskite material CsPbIBr₂and carbon electrode CsPbIBr₂PSCs as examples,the study investigated the effect of perovskite crystal film growth regulation and interface modification on device performance and stability.On one hand,by tailoring the stoichiometry of CsI to PbBr₂in the CsPbIBr₂precursor to 1.1:1.0,i.e.CsI-rich,the harmful PbBr₂self-doping phenomenon in the one-step spin-coated CsPbIBr₂film was suppressed,and a pure-phase,high-work function,low-defect density,and close-to-intrinsic doping CsPbIBr₂film was obtained.The performance of the device was improved,and the carbon-electrode,all-inorganic CsPbIBr₂PSC achieved a PCE of10.48%.On the other hand,TiO₂electron transport layer（ETL）was modified with CsBr clusters to promote the energy band alignment at the TiO₂ETL/CsPbIBr₂absorber,successfully suppressing the non-radiative recombination of charge carriers at the TiO₂/CsPbIBr₂interface,and achieving more efficient carrier extraction and transport.The device performance was further improved,and the carbon-electrode,all-inorganic CsPbIBr₂PSCs achieved a PCE of 10.71%.（2）Research on universal and low-temperature processes of large-area perovskite films deposition.Based on the aforementioned research,we have developed an improved spray coating process to prepare high-quality large-area perovskite films and devices,with a focus on the general and low-temperature processes in the industrialization of perovskites.Additionally,we have also developed a low-temperature process suitable for flexible devices.On the one hand,a water-based spray-assisted growth process was proposed for the universal preparation of large-area perovskite films.Based on this method,high-quality CsPbCl₃,CsPbBr₃,CsPbIBr₂,CsPbI₂Br,and MAPbI₃films were successfully deposited,and small-area devices with PCEs of 1.27%,10.22%,10.44%,13.30%and 18.37%were fabricated.In addition,a large-area CsPbBr₃film（100.00 cm²）with good uniformity and a large-area MAPbI₃PSM（active area:10.00 cm²）with a PCE of 15.73%were successfully prepared.This process provides a new route for the universal fabrication of efficient large-area PSMs.On the other hand,a PbBr₂film crystal orientation engineering strategy is proposed for the low-temperature preparation of high-quality CsPbBr₃films.By doping a suitable CsBr into the PbBr₂precursor,the preferred crystal orientation of the PbBr₂film is successfully tailored from[020]to[031],reducing the reaction energy barrier between it and the subsequently deposited CsBr and accelerating the reaction between the two.The annealing temperature was reduced from 250℃to 150℃,while still obtaining CsPbBr₃films with high purity,large grains,full coverage,and high crystallinity.With this method,not only can high-efficiency,carbon-electrode CsPbBr₃PSCs（PCE:10.27%）can be prepared with lower energy consumption,but also device with active area of 1.00 cm²,（PCE:8.00%）and high-efficiency flexible device（PCE:8.27%）can be successfully fabricated at low temperatures.This innovative process provides a viable approach for the low-cost production of large-area,high-efficiency PSCs and low-temperature preparation of flexible devices.（3）Controlled and stable fabrication of high-efficiency large-area MAPbI₃PSMs.A blade coating process with a wide processing window was proposed for the commonly used narrow-bandgap perovskite material MAPbI₃in large-area PSMs.By adding KSCN additive to the precursor,the evaporation rate of the precursor solvent was effectively reduced,and the nucleation and crystallization process of the film were retarded,thus widening the processing window.The introduction of K⁺suppressed the formation of Pb⁰and iodine vacancy defects in the film.Uniform,full-coverage,large-grain,high-crystallinity,and low-defect MAPbI₃films can be obtained over a wide range of air knife pressures.And,a large-area MAPbI₃film（25.00 cm²）with good uniformity was successfully deposited,and a large-area（active area:10.00 cm²）PSM with a PCE of17.62%was successfully achieved,and its operational stability and long-term storage stability were also improved.This process provides a new approach for the controlled,stable,and scalable production of high-efficiency large-area PSMs.（4）Co-doping strategy to enhance efficiency and stability of large-area,wide-bandgap PSMsA co-doping strategy has been proposed for the wide-bandgap perovskite material(FA_0.65MA_0.2Cs_0.15)Pb(I_0.8Br_0.2)₃applicable to perovskite/silicon tandem solar cells.By co-doping Pb（SCN）₂and PEACl into the perovskite precursor,perovskite films with larger grain size and fewer grain boundaries can be successfully deposited by air-assisted blade-coating process.In addition,the 2D perovskite（PEA）₂PbI_xCl_4-xformed at the grain boundaries effectively suppresses the harmful light-induced halide segregation phenomenon and improves the moisture resistance of the film.As a result,a four-terminal（4-T）perovskite/silicon tandem solar cell with a PCE of 30.53%and a large-area（active area:10.00 cm²）PSM with a PCE of 17.70%as well as excellent light-stability were successfully fabricated.The proposed co-doping strategy is expected to promote the practical application of perovskite/silicon tandem solar cells.