Investigation On Active Layer Modulation And Lead Leakage Suppression In High-efficiency Perovskite Solar Cells

In just a dozen years,the power conversion efficiency of perovskite solar cells has achieved rapid progress from 3.81%to more than 26%,outpacing other photovoltaic devices.However,there still exists a gap between the efficiency of perovskite solar cells and their theoretical limit,and stability issues of perovskite solar cells remain significant obstacles for commercialization.More importantly,lead is an indispensable component in current high-performance perovskite solar cells,yet it causes pollution to the ecological environment that is difficult to eliminate,and can also cause irreversible damage to the human body.Focusing on this,this dissertation studies from the perspective of active layer modulation and lead leakage suppression.Via methods including active layer modification,crystallization regulation,grain boundary passivation and device encapsulation,targeted research has been carried out on issues such as improving device performance and stability and suppressing lead leakage.The main research contributions and innovations of this dissertation are as follows:（1）Study on the active layer modulation of perovskite solar cells and the lead leakage suppression by surface modification of thiol molecules 1,2-EDT.The thiol group contained in 1,2-EDT anchors the uncoordinated Pb²⁺on the surface of the perovskite,improving the crystallization quality of the perovskite.The study shows that 1,2-EDT reduces the defect state density of perovskite films and improves the energy level arrangement of the perovskite surface as well as perovskite/hole transport layer interface,thus suppressing recombination loss of carriers and improving carriers transport.The elimination of defect states and the regulation of energy levels by 1,2-EDT have been verified through first-principles calculations.Due to the improvement of film quality and charge transfer,the 1,2-EDT modified device achieves a V_oc of 1.12 V and a PCE of 21.00%.In addition,the improvement of hydrophobicity and suppression of defects of the perovskite film after 1,2-EDT modification enables the device to maintain 87%of its initial efficiency after 1005 hours of storage.Finally,the study proves that the modification of 1,2-EDT retards the decomposition of the perovskite film in water and effectively suppresses lead leakage of the perovskite film and devices.（2）Study on the lead leakage suppression by chelating resin IDA-CR encapsulation.IDA-CR has a water-insoluble conjugated backbone and a large number of iminodiacetic acid functional groups.The study shows that IDA-CR has a large specific surface area,ensuring effective contact and adsorption of Pb²⁺.Through the simulation of the lead adsorption molecular dynamics process,it is verified that the adsorption of Pb²⁺by IDA-CR is more consistent with the pseudo-second-order molecular dynamics model,and the surface chemical adsorption is the dominant role in the process.Due to the excellent chelating effect of the iminodiacetic acid functional group on Pb²⁺and the large specific surface area,the surface of IDA-CR can effectively adsorb Pb²⁺.More importantly,IDA-CR does not cause performance loss but improves the long-term stability of the devices.In addition,both qualitative and quantitative analysis results prove that IDA-CR has good ability to suppress lead leakage.In simulations of heavy rain,acid rain and high temperature environments,IDA-CR/glass encapsulation effectively alleviates the decomposition of the perovskite film and achieved effective suppression of lead leakage.（3）Study on the active layer modulation by the Lewis base additive DBP and lead leakage suppression by the self-healing Pm A encapsulation.The addition of DBP increases the perovskite grain sizes and regulates the grain growth direction.In addition,the C=O groups and benzene ring structures contained in DBP can simultaneously passivate Pb and I inside the perovskite film and reduce the defect state density of the perovskite film.The study also shows that DBP increases work function of the perovskite film,optimizes the energy level arrangement of the perovskite/electron transport layer interface,and promotes the interfacial transport of carriers.Finally,the device based on DBP additive achieves a V_oc of 1.17 V and a PCE of 22.53%,maintaining 84%of its initial efficiency after 1000 hours of storage.The large number of hydrogen bonds contained in Pm A allows it to self-heal under low temperature driving after being scratched,improving mechanical stress resistance of the encapsulation.In addition,Pm A contains abundant carbonyl and amine groups,which can anchor and chelate Pb²⁺.Due to its excellent physical and chemical encapsulation properties,Pm A greatly slows down the decomposition rate of the perovskite film in deionized water,showing effective suppression of lead leakage.（4）Study on the active layer modulation of perovskite solar cells and the lead leakage suppression by self-polymer doping.The regulation effect of three self-polymers NMA,NHEMAA and AHPAA on perovskite films and their influence on device performance are systematically studied.The study confirms that NMA and NHEMAA can self-polymerize driven by the perovskite annealing temperature of 150°C,and the resulting self-polymer can effectively passivate defects at the perovskite grain boundaries.However,AHPAA does not self-polymerize at this temperature,resulting in excess monomer remaining at the grain boundaries,affecting the crystallization of perovskite.Characterization by FT-IR and XPS confirms the interaction between the carbonyl or amine groups contained in the three self-polymers with the excess Pb or I in the perovskite film.NHEMAA fully and effectively passivates the perovskite grain boundaries,achieving a PCE of 22.6%and a V_oc of 1.16 V.Self-polymer-doped perovskite films also exhibit better humidity stability.The doping of NHEMAA and NMA achieves excellent long-term device stability and humidity stability.In addition,the grain boundary encapsulation effect of NHEMAA and NMA effectively suppresses lead leakage of the device.