《Nature(IF>69.504)》Perovskite Interface Structure Optimization Enables 28.5% Efficient Tandem Solar Cells-Recent Research by Hairen Tan's Team
Highlights
- The research team introduced a double-layer perovskite heterojunction at the interface of lead-tin mixed perovskite/electron transport layer, which effectively suppressed interfacial recombination and improved charge extraction efficiency.
- By depositing a layer of lead halide wide bandgap perovskite on top of the lead-tin mixed perovskite to form a double-layer heterojunction, the efficiency of the mixed perovskite solar cell increased to 23.8%.
- Applying the double-layer heterojunction structure in the mixed perovskite subcells enabled all-perovskite tandem solar cells to achieve a record efficiency of 28.5%. The encapsulated tandem cells maintained over 90% of their initial efficiency after 600 hours of illumination.
Background
All-perovskite tandem solar cells have the advantages of broad spectral utilization and low thermal loss, and are considered a strong candidate for next-generation photovoltaic technology. However, the lead-tin mixed perovskite bottom cells reported previously suffer from insufficient open-circuit voltage and fill factor, which is mainly caused by severe non-radiative recombination at the interface between the perovskite and electron transport layer. Constructing a mixed 2D/3D heterojunction is the most studied method to inhibit interfacial recombination, but the 2D layer increases resistance and affects charge transport.
Results
The team led by Hairen Tan at Nanjing University introduced a 3D/3D double-layer perovskite heterojunction with a type II band alignment at the interface of lead-tin mixed perovskite/electron transport layer. A layer of lead halide wide bandgap perovskite was first deposited on the surface of the mixed perovskite, and then converted into perovskite by solution processing to form a double-layer heterojunction. This structure facilitates charge extraction. The open-circuit voltage and fill factor of the mixed perovskite solar cells increased significantly, achieving an efficiency of 23.8%.
Applying the double-layer heterojunction in the mixed perovskite subcells enabled the all-perovskite tandem solar cells to achieve a record efficiency of 28.5%. The encapsulated tandem cells maintained over 90% of their initial efficiency under continuous illumination for 600 hours. This is mainly because the double-layer heterojunction suppresses interfacial recombination and increases the charge transfer rate.
Methods
- A lead halide perovskite thin layer was coated on the surface of the mixed perovskite by solution processing and evaporation to form a double-layer heterojunction.
- The morphology and structure of the double-layer heterojunction were characterized by scanning electron microscopy, X-ray diffraction, etc.
- The photovoltaic parameters of mixed perovskite solar cells with and without heterojunction were measured and compared.
- Carrier dynamics of the heterojunction were studied by steady-state and time-resolved photoluminescence, ultrafast transient absorption and other methods.
- The double-layer heterojunction was introduced into the mixed perovskite subcells to fabricate all-perovskite tandem solar cells. The parameters of the subcells were tested and optimized to achieve high efficiency.
- The tandem solar cells were encapsulated and their stability under illumination was tested.
Conclusion
This study introduced a 3D/3D double-layer heterojunction at the interface of mixed perovskite solar cells, which effectively suppressed interfacial recombination and achieved high efficiency of 23.8% for single mixed perovskite cells. Applying this double-layer heterojunction structure to all-perovskite tandem cells further enhanced the efficiency to 28.5% with good stability. The results provide new insights into interfacial design of perovskite solar cells and development of efficient tandem cells.
Supplementary Figure 14 | ToF-SIMS 3D maps of control and PHJ Pb-Sn
perovskite film. Reconstructed, background subtracted 3D maps showing the
distributions of Pb2+ and Sn2+ ions of narrow bandgap (a) control, (b) PHJ.
Supplementary Figure 18 | ToF-SIMS 3D maps of control and PHJ Pb-Sn
perovskite film. Reconstructed, background subtracted 3D maps showing the
distributions of Iand Brions of (a) control, (b) PHJ, (c) PHJ film storage in glovebox
60 days narrow bandgap perovskite films. The raster area of the primary ion beam was
100 μm×100 μm, and the thickness axis has been expanded for clarity.
Supplementary Figure 22 | PV performance of Pb-Sn PSCs. PV performance of
control and PHJ Pb-Sn narrow-bandgap perovskite solar cells, and control devices with
1% and 2% Br added.
Supplementary Figure 24 | J-V curves of control and PHJ devices with absorber
layer thicknesses of 1,200 nm. Control BCP: control Pb-Sn PSCs with C60/BCP as the
ETL; Control ALD-SnO2: control Pb-Sn PSCs with C60/ALD-SnO2 as the ETL; PHJ
BCP: PHJ Pb-Sn PSCs with C60/BCP as the ETL; and PHJ ALD-SnO2: heterojunction
Pb-Sn PSCs with C60/ALD-SnO2 as the ETL. (Detailed parameters showing in
Supplementary Table 5).
Supplementary Figure 31 | Dark J-V curves of the control and PHJ Pb-Sn
perovskite devices.
Supplementary Figure 37 | Photovoltaic performance of wide-bandgap perovskite
solar cells. a, Statistics of PV parameters among 62 devices. b-c, J-V, EQE and total
absorptance (1-R) curves of the best-performing WBG device.
Supplementary Figure 38 | Photovoltaic performance of WBG, NBG subcell and
tandem solar cells. a, J-V curves of wide-bandgap PSCs with bare VNPB and SAM
modified NiO as the HTL. b, J-V curves of control and PHJ narrow-bandgap PSCs. cd, J-V and EQE curves of tandem solar cell with different subcells. The integrated Jsc
values of WBG and NBG subcells from EQE spectra shows that there is an agreeing
well current density matching between the subcells for different tandem solar cells (the
photovoltaic performance parameter shown in Supplementary Table 13).
