A research team led by Researcher Bu Tongle of Wuhan University of Technology published a research paper titled "Homogeneous coverage of the low-dimensional perovskite passivation layer for formamidinium–caesium perovskite solar modules" in the journal Nature Energy. Team member Li Jing serves as the first author, and Researcher Bu Tongle serves as the corresponding author.
Key Highlight: This paper develops a universal strategy for incorporating formamidinium (FA) cations into a large-scale organic passivator to achieve a phase-pure n-value 2D perovskite cap layer with uniform morphology. Based on this antisolvent-free deposition strategy, the team achieved peak active area efficiencies of 25.61%, 24.62%, and 23.60% for small-sized devices (0.14 cm²), large-sized devices (1.04 cm²), and micromodules (13.44 cm²), respectively, with relatively minimal efficiency loss as the active area increases.
When scaling up devices to modules, the formation of a uniform passivation layer based on phase-pure two-dimensional (2D) perovskites is a challenge for perovskite solar cells. To address this issue, a team led by Researcher Tongle Bu of Wuhan University of Technology has proposed an effective and scalable passivation strategy. By suppressing unfavorable phase separation in composition and dimensionality, they can uniformly form a phase-pure 2D perovskite overlayer on a 3D perovskite surface. This strategy addresses the chain-length-dependent and halide-related phase separation issues of 2D perovskites grown on 3D perovskites. They demonstrate that treating the perovskite layer with bromoformamidine in the presence of a long-chain (bbb10) alkylamine ligand salt can form a uniform 2D perovskite passivation layer. For small (0.14 cm²) and large (1.04 cm²) devices, as well as a small module (13.44 cm²), they achieve world-class active area efficiencies of 25.61%, 24.62%, and 23.60%, respectively, with antisolvent-free processing.
Furthermore, the solar micromodules achieved a T80 lifetime exceeding 2000 hours under MPPT, demonstrating excellent stability. Most notably, large-scale PSMs (20 cm × 20 cm and 30 cm × 30 cm) exhibited champion efficiencies of 18.90% and 17.59% at aperture areas of 310 cm² and 802 cm², respectively. This homogeneous low-dimensional structure passivation strategy has considerable potential for accelerating the commercialization of PSMs.
Fig. 1 | Compositional engineering of the 2D perovskite phase for scalable solar modules. a, Chemical structure of 2D ligands (RX) for passivation of perovskite films. RX represents the ammonium halides, in which R and X are organic ammoniums (depicted on the left-hand side) and halides (depicted on the right-hand side), respectively. BA, n-butylammonium; OA, n-octylammonium; DA, dodecylammonium; HDA, hexadecylammonium; PMA, phenmethylammonium; PEA, phenylethylammonium; NMA, 1-naphthylmethylammonium; PRMA, 1-pyrenemethylammonium. b, The schematic diagram of PSM with the structure of glass/FTO/SnO2/perovskite/passivator/spiro-OMeTAD/Au. c–e, PL (left) and local enlarged PL (right) spectra of perovskite films post-treated with different organic RX salts (c), DAX (d) and DAX/FABr (e). The grey box and coloured arrows in c highlight the appearance of n = 1 2D phase separation, which is observed in HDAI (pink arrow), DAI (blue arrow) and DACl (green arrow) samples. The vertical dashed lines indicate the PL peak position. f–h, Calculated formation enthalpies of R2PbI4 (n = 1) (f), DA2PbI4−xClx (n = 1) and DA2Pb(I2−0.5xCl0.5x)Br2 (n = 1) (g), and DA2FAPb2(I4−0.5xCl0.5x)Br3 (n = 2) and DA2FA2Pb3(I6−0.5xCl0.5x)Br4 (n = 3) (h). The y-axis break in g enables intuitive data comparison.
Fig. 2 | Growth kinetics and formation mechanism of the homogeneous 2D phase structure. a, In situ PL measurements of perovskite films with different organic salts post-treatment during spin coating. b, PL intensity evolution of the 3D perovskite phase derived from in situ PL measurements. The grey dashed lines and arrows with numbers highlight a turning point in the evolution of PL intensity. c, 2D GIWAXS data of perovskite films post-treated with different salts after annealing. d, 1D integrated intensity of 2D GIWAXS data along the out-of-plane scattering vectors, qz. e, The top-view and the cross-sectional SEM images of perovskite films post-treated with different organic slats. The yellow circles highlight distinct features of morphology. f, Schematic diagram of self-assembled different organic salts on the 3D perovskite surface producing different surface structures. V, vacancy.
Fig. 3 | Homogeneous surface morphology and defect passivation. a–d, AFM (a) and KPFM (c) images of different perovskite films (from left to right: pristine 3D, DABr- and DABr/FABr-treated perovskites) and the corresponding statistical distribution of height (b) and surface potential (d) derived from a and c, respectively. The curves on top of the data fit a Gaussian distribution. e,f, Timeresolved confocal PL mappings (e) and the trap densities (Nt) calculated from the dark current–voltage (I–V) curves of hole-only and electron-only devices (f) for the control,DABr-treated and DABr/FABr-treated perovskite films. g,h, In situ PL mapping of perovskite films post-treated with different organic salts (from left to right: pristine 3D, DABr- and DABr/FABr-treated perovskites) under continuous LED light source irradiation (g) and corresponding PL intensity evolution of the 3D peak (h).
Fig. 4 | Photovoltaic performance and stability characterization. a, J–V curves of small-sized devices with the post-treatment of different organic salts. b, J–V curve of the champion devices with the post-treatment of DABr/FABr. Inset: the corresponding photograph of a 1.04-cm2 large-sized device. c, EQE curve of the large-sized device with the post-treatment of DABr/FABr. d, J–V curve of the champion mini-module with the post-treatment of DABr/FABr. Inset: the photograph of a mini-module. e, Continuous MPP tracking for the encapsulated mini-module in ambient air. FF, fill factor; FS, forward scan; RS, reverse scan.
Fig. 5 | Scalable printed large-area modules. a, Schematic illustration for the scalable fabrication of large-sized PSMs with the corresponding laser processing (green cylinder) and the chemical bath deposition of large-scale SnO2 films (bottom inset). b, Photograph of a 30 cm × 30 cm PSM. c, J–V curve of the champion 20 cm × 20 cm sub-module with a series connection of 26 subcells. d, J–V curve of the champion 30 cm × 30 cm small module with a series connection of 42 subcells. PCEap, aperture-area efficiency; PCEac, active-area efficiency.
文章来源：DOI: 10.1038/s41560-024-01667-8
https://doi.org/10.1038/s41560-024-01667-8