Molecular Interface Engineering Unlocks 22% DJ Perovskites

May 29, 2026 08:24 AM ET

• Dual-anchoring croconic and squaric acids engineer Dion-Jacobson perovskites with vertical crystallization, better orientation and defect passivation—boosting efficiency to 22.03% and improving durability.

Researchers at Nankai University, Ningbo University and the Chinese Academy of Sciences report a molecular interface engineering approach for Dion-Jacobson (DJ) perovskite solar cells, using dual-anchoring organic acids to drive vertical crystallization and boost performance and durability. The work targets charge-transport losses caused by unfavorable crystal orientation in 2D perovskites.

Croconic acid and squaric acid (CA and SA) were inserted between the NiOx hole-transport layer and an (TTDMA)-based DJ perovskite (n=4). CA forms a disordered layer, while SA—via bidentate coordination—creates an ordered vertical template that improves crystallinity and orientation. SA also passivates defects, relieves strain, aligns energy levels, and suppresses iodide oxidation from Ni3+. Cells reached a 22.03% champion efficiency (21.42% certified) and improved stability, with the strategy extended to Ruddlesden-Popper perovskites.

How do CA and SA enhance DJ perovskite crystallization and stability for 22% efficiency?

• CA (croconic acid) helps nucleation by creating a more flexible, “disordered” interfacial environment at the NiOx/perovskite boundary, so the DJ perovskite can start growing readily and fill out the film more uniformly rather than forming misoriented domains.
  
• By tuning the initial interfacial chemistry, CA reduces the likelihood of unfavorable grain orientations—one of the major sources of charge-transport losses in Dion–Jacobson (2D) perovskites where stacked layers strongly control carrier pathways.
  
• SA (squaric acid) acts as the primary ordering agent: its molecules coordinate in a more rigid, bidentate fashion to the adjacent surface/ions, producing an ordered “vertical template” that steers crystal growth along the desired out-of-plane orientation.
  
• The vertical templating effect improves perovskite crystallinity (fewer structural defects and lower density of crystallographic disorder), which supports more efficient charge transport and reduces recombination.
  
• CA and SA work together as complementary interfaces: CA facilitates formation and coverage of the perovskite, while SA enforces the orientation and packing quality after nucleation—leading to a more coherent 2D layered lattice throughout the film.
  
• SA also passivates interfacial and bulk-like defect sites associated with imperfect stacking in n=4 DJ perovskites, decreasing nonradiative recombination and improving the open-circuit voltage component that typically limits high efficiency.
  
• Strain relief at the interface is enhanced through the ordered coordination network from SA, helping the perovskite maintain its layered structure during operation and during film formation thermal/solvent steps.
  
• Improved energy alignment at the NiOx/perovskite interface (helped by SA’s controlled interfacial chemistry) reduces interfacial charge-transfer resistance, helping maintain current extraction at high efficiency.
  
• SA suppresses deleterious interfacial redox chemistry involving NiOx (notably pathways that can promote iodide-related degradation), improving chemical stability under illumination and elevated humidity/thermal stress.
• The net result of (i) guided vertical crystallization, (ii) reduced defect density, and (iii) stronger chemical/structural protection at the NiOx contact is a champion device performance around 22% (with improved durability), as reported for the n=4 DJ perovskite architecture.