Northwestern University scientists created a two-molecule fluid solution capable of fixing structural faults in perovskite solar cells without leading to chemical aggregation.
By adding bulky molecular shields to acidic and basic passivation molecules, scientists were able to prevent these chemical solutions from coming into contact with one another prematurely.
Such a method of chemical treatment made it possible for both chemicals to neutralize different surface traps in the perovskite crystal structure, resulting in a peak power conversion efficiency (PCE) of 27.4 percent (with an independently certified steady-state value of 25.8 percent).
Preventing self-assembly in molecular passivation treatments
Unbonded lead and halide atoms provide micro-scale traps on the surface to trap electrons passing through a perovskite film used in solar cells.
Chemists coat the surface of such films using liquid-based acid and basic passivating agents to plug any electronic leakage.
Mixing such molecules with opposite charges results in an immediate reaction as their chemical groups bind with each other.
Bulky molecular structures on the passivating agents prevent them from prematurely binding with each other.
Steric and electronic constraints suppress mutual binding while allowing each passivator to independently target and neutralize appropriate surface defects.
Dual-defect site targeting on perovskite crystal surfaces
Sterically hindered Lewis bases interact with exposed lead cations.
Lewis acids target halide vacancies without colliding with the basic molecules.
Thus, dual-targeting results in blocking of both surface traps without interfering with the rest of the crystal structure.
The elimination of both defects provides for an unobstructed electric flow from generated power to collecting plates.
Achieving high-performance defect passivation in the laboratory
Perovskite films riddled with defects generate heat from sunlight absorbed by constantly recombining charge carriers internally.
Liquid dual-molecule treatment prevents formation of surface traps at active interface films, reducing voltage losses in lighting.
The peak conversion efficiency of the perovskite solar cell was measured at 27.4 percent.
Agglomeration was halted.
Blocking premature molecular association doubled the number of active crystal sites passivated at the surface.
Solar cells remained efficient despite operation for several hundred hours.
Maintaining operational stability under continuous thermal stress
The Perovskite films corrode quickly while operating due to the unpassivated surface defects that capture moisture from the air.
Moisture causes damage to the weakly bound lead halides inside, reverting them to their original inactive salts.
The hydrophobic hydrocarbon rings of the passivating agents form an effective layer to repel the water molecules.
Water forms beads over the barrier and gets washed away without reaching the deeper crystal junctions.
The thermal test results indicated that treated devices could maintain 90 percent efficiency within one thousand hours at 185° F.
Formation of a water-repellent shield prevents corrosion without causing any electronic malfunction in the inner structures, as reported by Northwestern University.
Chemical synthesis costs evaluation and limitations related to scaling up in an industry
Sterically gated molecules have set new laboratory efficiency records, yet multi-step organic synthesis results in increased cost of chemical production.
Specific purification steps of hydrocarbon ring attachments involve increased cost compared to common commercially used passivating chemicals.
It is necessary to estimate if the performance gains achieved by this treatment are worth the additional costs of chemical synthesis in industrial processes.
There is a danger of uneven distribution of the molecules during high-speed roll-to-roll liquid deposition technology.
There is a risk of accumulation of unpassivated defects at the edges of commercial panels because of chemical localization.
It will be decided based on the feasibility of adapting the precision liquid coating technique to the commercial industry.
The full study can be found here: Shin, D., Kitade, S., Duan, L. et al. Sterically gated Lewis acid and base pairs enable orthogonal defect passivation in perovskite solar cells. Nat. Chem. (2026). https://doi.org/10.1038/s41557-026-02261-z
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