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Abstract:

Substantial VOC loss and halide segregation in wide-bandgap (WBG) perovskite sub-cells pose significant challenges for advancing all-perovskite tandem solar cells (APTSCs). Regarding this, one of the most impactful developments is the application of hole-selective self-assembled monolayers (SAMs), leading to the advancement in APTSC technology. However, SAMs with poor polar-solvent resistance would be inevitably delaminated from substrates during perovskite precursor coating, remaining great challenge in achieving a complete SAMs coverage with derivatization issues, e.g. defective perovskite and considerable interface energy loss. Here, we introduced an in-situ molecular compensation strategy to address the inherent flaw of SAMs within WBG perovskites via incorporating 5-ammonium valeric acid iodide (5-AVAI). The larger-dipole 5-AVAI spontaneously accumulates toward the buried interface to compensate the SAMs-deficient sites when depositing WBG perovskite, effectively minimizing interfacial energy loss. Simultaneously, amphoteric 5-AVAI with amino and carboxyl groups can compensate the defects at grain boundaries for solid passivation. Consequently, a champion efficiency of 20.23% with a record VOC of 1.376 V was realized on WBG devices, enabling an efficiency of 28.9% for the APTSCs. Encouragingly, the tandems showed good operational stability and retained 87.3% of their efficiency after 800 hours of tracking.

Abstract:

ABSTRACT Reducing non‐radiative charge‐carrier recombination at both p‐ and n‐side interfaces of the perovskite layer is crucial for realizing high‐voltage single‐ and multi‐junction solar cells. Herein, it is demonstrated that co‐depositing a mixture of ethane‐1,2‐diammonium iodide and different oleyl‐based amphiphiles renders a passivator‐insulator modification at the perovskite–C 60 interface, which suppresses n‐side contact losses in narrow‐bandgap (∼1.26 eV) Sn–Pb perovskite solar cells. Interestingly, a cationic oleyl‐based amphiphile introduced concurrently with the poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate hole‐transport‐layer, deposited from an aqueous dispersion in 1‐propanol, also reduces the p‐side energy loss by providing a substrate for high‐quality perovskite films and limiting the contact between the doped hole‐transport‐layer and the perovskite layer atop. This double‐sided interface modification strategy enables open‐circuit voltage ( V oc ) values of up to 0.91 V—over 91% of the detailed‐balance limit—for 22.6% efficient single‐junction Sn–Pb perovskite solar cells. Monolithic all‐perovskite tandem solar cells show V oc and efficiency values of up to 2.16 V and 26.1%, respectively. The results demonstrate that insulating‐passivating interface modifications between the perovskite and charge transport layers represent an effective strategy for reducing energy losses in emerging perovskite solar cell technologies.

Abstract:

ABSTRACT Perovskite solar cells have achieved high efficiencies but remain limited by instabilities. For the opaque metal rear electrode, Au is commonly used to achieve stable operation but is impractical for scalable photovoltaics due to cost. We investigate the effect of a 5 nm chromium (Cr) interlayer beneath low‐cost metals (Al, Ag, Cu) to inhibit metal interdiffusion. Cr/Al electrodes yield devices with high efficiencies (up to 24.7%) and operational stability comparable to reference devices using Au rear electrodes under heat and light stress, with raw material costs reduced by five orders of magnitude. At the front semi‐transparent electrode, through which sunlight will be incident, we identify indium diffusion from indium tin oxide (ITO) as a key degradation mechanism, revealed via depth‐resolved mass spectrometry. We demonstrate that replacing ITO with fluorine‐doped tin oxide (FTO) substantially improves stability. Combining both improvements, FTO with Cr/Al contacts, produces devices retaining >66% of the initial efficiency after >1000 h ageing at 75 °C under simulated sunlight. These results highlight the critical role of electrode selection on perovskite solar cell durability and provide a practical route toward stable and cost‐effective perovskite photovoltaics.

Abstract:

Robust interconnecting layers are critical for all-perovskite tandems but are typically limited by acidic poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and interdiffusive gold, compromising stability. Here, we substitute PEDOT:PSS with a conjugated polyelectrolyte-modified bithiophene-triphenylamine small molecule as the hole transport layer for tin-lead perovskite subcells, ensuring superior hole extraction and interfacial robustness. The gold recombination junction is replaced with a 5-nm-thick sputtercoated indium-doped zinc oxide to eliminate metal diffusion and minimize parasitic absorption. This design yields certified efficiencies of 29.80% and 30.19% for double-junction tandems employing methylammonium (MA)-free and MA-containing narrow-band-gap subcells, respectively. Furthermore, 1.0-cm² devices and 11.3-cm² mini-modules show efficiencies up to 28.7% and 25.0%, respectively. Encouragingly, encapsulated tandems maintain 90% of their initial efficiency after over 770, 530, and 220 h of maximum power point tracking under illumination at 45^◦C, 65^◦C, and 85^◦C, respectively. This work presents a viable route beyond PEDOT:PSS for narrow-band-gap perovskites toward reliable all-perovskite tandem photovoltaics.

Abstract:

Narrow-bandgap tin and mixed tin-lead halide perovskites are attracting growing interest for optoelectronic applications, yet the difficult-to-control crystallization process has hindered their development. Although additive engineering has effectively improved film formation, the fundamental origins of their distinct crystallization behavior remain less explored. Here, through direct comparison with Pb counterparts, we investigate the pre-crystallization stages of Sn-based perovskite precursor solutions through complementary structural characterizations. We show that Sn precursors are intrinsically more reactive and sensitive to their chemical environment, exhibiting poorer colloidal stability compared to Pb and a strong inherent tendency to agglomerate. These findings explain their narrower processing window, where small variations in solution chemistry strongly affect nucleation and crystallization dynamics. To fabricate high-quality tin-based perovskite through solution methods, we highlight the importance of controlling the often-overlooked pre-crystallization stages, though, for example, rational solvent and additive designs. Overall, we provide fundamental insights into precursor solution chemistry and establish pre-crystallization engineering as a key strategy for overcoming long-standing limitations in thin-film fabrication, particularly in light of the field's rapid progression toward large-scale, sustainable, and solvent-conscious manufacturing.