Research On Highly Efficient Perovskite Solar Cells Based On Interface Dimensional Regulation

In recent years,perovskite solar cells(PSCs)have attracted much attention owing to their excellent optoelectronic properties and lower material cost.PSCs are categorized into regular-type(n-i-p)and inverted-type(p-i-n)structures.Due to the smaller J-V hysteretic behavior,low fabrication temperature,transparent carrier transport layers,and higher environmental stability,p-i-n structured PSCs has become one of the mainstream battery structures today.At the same time,due to the continuous adjustable light absorption range of perovskite materials,wide-bandgap(E_g=1.65～2.1 eV)PSCs of trans-structure are often used in the top structure of double-junction and triple-junction solar cells,which has become one of the difficulties and hot spots in current research.In order to widen the optical bandgap of perovskite materials,it is usually necessary to introduce more bromine ions(Br~-)into the crystal structure.However,there are serious defects in Br~--rich perovskites’materials such as non-radiative recombination of auxiliary carriers and phase segregation induced by ion migration,which greatly limit the open-circuit voltage and power conversion efficiency(PCE)of devices,and become the bottleneck of the efficiency development of multijunction cells in the future.To address such issues,this work focuses on ion migration at the perovskite/electron transport layer interface withinin the p-i-n device structure.Based on the physical mechanism of inhinited ion migration in the low-dimensional structure,dimensional regulation is accordingly carried out at the interface of perovskite/electron transport layer.This work aims to solve the halide phase separation problem of wide-bandgap materials in double-junction or even triple-junction tandem solar cells and provide experimental basis for further efficiency breakthrough of perovskite tandem solar cells.The main research results are as follows:Focusing the perovskite/Si double-junction tandem solar cell model,a study of ternary wide-bandgap perovskites with ternary cations andnd an E_g of 1.66 eV was carried out.Based on the interface dimensional regulation strategy,the inhibiting effects of compounds based on PEA~+large cation with different halide counterions in the phase separation of wide-bandgap perovskite was investigated in depth,and the wide-bandgap perovskite materials with relatively stable phase under continuous illumination such as laser power and standard one-sun intensity were achieved.This work successfully inhibits the surface defects and improves the carrier lifetime of perovskites.It clarifies the mechanism of phase segregation inhibition and defect passivation of PEABr at the interface of perovskite/electron transport layer.At the same time,invert-structured1.66eV-bandgap PSCs with a PCE of 19.78%is achieved.In view of the serious phase separation problem of wide-bandgap perovskite(E_g=1.97 eV)as top cells in triple-junction solar cells,this work further expands and verifies the universality of interface dimensional modification strategy in inhibiting halogen phase separation.Low-dimensional interface structure is designed and prepared,which effectively inhibits the phase segregation problem of Br~--rich wide-bandgap perovskite.The density of interfacial defects is correspondingly reduced.Finally,through the interface dimensional control strategy,open-circuit voltage of the 1.97eV-bandgap PSCs is 1.30 V with the device efficiency being 12.9%,reaching the frontier level worldwide,thus laying an important foundation for the advancement of triple-junction tandem solar cells.