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Iodide and bromide integration facilitate bandgap tunability in wide-bandgap perovskites, yet high concentrations of bromide lead to halide phase segregation, adversely affecting the efficiency and stability of solar cell devices. In this work, 2-amino-4,5-imidazoledicarbonitrile (AIDCN), with highly polarized charge distribution and compact molecular configuration, is incorporated into a 1.86 eV wide-bandgap perovskite to effectively suppress photoinduced iodine escape and phase segregation. Hyperspectral photoluminescence microscopy reveals that AIDCN mitigates phase segregation under continuous laser exposure. Concurrent in situgrazing-incidence wide-angle X-ray scattering and X-ray fluorescence measurements further validate suppressed iodine escape, evidenced by a notable slowing down of lattice shrinkage and a well-maintained overall chemical composition of the perovskite under continuous illumination. Applying this approach, we achieve a power conversion efficiency (PCE) of 18.52% in 1.86 eV wide-bandgap perovskite solar cells. By integrating this perovskite subcell with the PM6:BTP-eC9 organic subcell, the tandem attains a maximum PCE of 25.13%, with a certified stabilized PCE of 23.40%.

Perovskite bandgap tuning without quality loss makes perovskites unique among solar absorbers, offering promising avenues for tandem solar cells1,2. However, minimizing the voltage loss when their bandgap is increased to above 1.90 eV for triple-junction tandem use is challenging3–5. Here we present a previously unknown pseudohalide, cyanate (OCN−), with a comparable effective ionic radius (1.97 Å) to bromide (1.95 Å) as a bromide substitute. Electron microscopy and X-ray scattering confirm OCN incorporation into the perovskite lattice. This contributes to notable lattice distortion, ranging from 90.5° to 96.6°, a uniform iodide–bromide distribution and consistent microstrain. Owing to these effects, OCN-based perovskite exhibits enhanced defect formation energy and substantially decreased non-radiative recombination. We achieved an inverted perovskite (1.93 eV) single-junction device with an open-circuit voltage (VOC) of 1.422 V, a VOC× FF (fill factor) product exceeding 80% of the Shockley–Queisser limit and stable performance under maximum power point tracking, culminating in a 27.62% efficiency (27.10% certified efficiency) perovskite–perovskite–silicon triple-junction solar cell with 1 cm2aperture area.

Remarkable progress has been made in perovskite solar cells (PSCs) recently. However, the defects present in the perovskite layer act as non-radiative recombination centers to decrease the stability and restrict the further performance improvement of the device. We report herein a sulfur-rich two-dimensional small molecule, SMe-TATPyr, as a bifunctional layer to efficiently passivate the surface defects of perovskite and facilitate the hole transfer at the perovskite/spiro-OMeTAD interface. X-ray photoelectron spectroscopy analyses show that the sulfur atoms of SMe-TATPyr can passivate the uncoordinated Pb2+defects and suppress the Pb0defect formation as Lewis bases. As a result, the power conversion efficiency of PSCs is distinctly increased from 20.4% to 22.3%. Moreover, this simple interfacial modification could effectively enhance the stability of unencapsulated PSCs to retain 95% of the initial efficiency after storage for 1500 h at ambient conditions, in contrast to 70% efficiency retention of the device without SMe-TATPyr under the same conditions.