Research On Hole Transport Layers Of Perovskite/Silicon Tandem Solar Cells

The power conversion efficiency（PCE）of crystalline silicon（c-Si）cells is approaching the theoretical efficiency limit.The monolithic tandem solar cell,which combines a wide bandgap top cell with a narrow bandgap crystalline silicon cell,is a feasible way to break through the efficiency limit of single-junction silicon solar cells.The perovskite solar cells（PSCs）have been rapidly developed,and their advantages of tunable bandgap,sharp light absorption edge,flexible fabrication process,and high efficiency make them suitable as wide bandgap top cells for monolithic tandem solar cells.The highest PCE of monolithic perovskite/silicon tandem solar cells has reached29.8%.The optimization of open-circuit voltage(V_OC)and short-circuit current density(J_SC)is crucial for realizing efficient tandem devices.The hole transport layer（HTL）is important for the V_OC of the tandem cells.Current matching and reflection loss are the key factors for the J_SC of the tandem cells.To realize efficient monolithic perovskite/silicon tandem solar cells,the contents of this thesis are presented as follows:（1）Polymer/Ni O_x bi-HTL.Ni O_x films were deposited by sputtering at room temperature.The surface defects of Ni O_x were modified with a polymer to form a bi-HTL.It is known that the properties of the polymer films would affect by the stacking of polymer chains.So,the halogenated aromatic solvent（chlorobenzene）and alkyl aromatic solvent（toluene）were introduced to optimize the chain conformations of the polymer.The toluene solvent enhanced theπ-πstacking of poly[bis（4-phenyl）（2,4,6-trimethylphenyl）amine]（PTAA）along the face-on orientation,thus the optimized bi-HTL with improved charge transportation and high conductivity was obtained.The surface of bi-HTL prepared by toluene solvent was smoother and more hydrophobic,which facilitated the deposition of high-quality perovskite films with large grain sizes.As a result,the PSC with optimized bi-HTL exhibited a PCE of 20.21%with a V_OC of1.163 V.（2）Efficient monolithic perovskite/silicon tandem solar cells.By optimizing the HTLs of top cells,it was found that either PTAA or Ni O_x would cause voltage loss in the tandem devices,while Ni O_x/PTAA bi-HTL can significantly reduce the voltage loss,indicating that the bi-HTL enabled the perovskite and silicon sub-cells to be effectively connected in series.To reduce the reflection losses of the tandem devices,Mg F₂ and textured polydimethylsiloxane（PDMS）anti-reflection coatings were introduced.The textured PDMS can better suppress the reflection in the near-infrared region,which increased the current density of the tandem devices by 9.61%.Next,the bandgap of the perovskite was tuned from 1.60 e V to 1.78 e V.When the band gap of the perovskite was 1.72 e V,the tandem device achieved a good current matching and exhibited a PCE of 22.40%.Finally,fullerene(C₆₀)was used as the electron transport layer instead of[6,6]-phenyl-C₆₁-butyric acid methyl ester（PCBM）in tandem devices.As a result,the tandem device exhibited a PCE of 24.34%with a J_SC of 16.74 m A cm^-2,a V_OC of 1.811V,and a fill factor（FF）of 80.28%.