The
energy level alignment at interfaces of perovskite solar cells
(PSCs) is an essential factor determining their efficiency and stability.
Therefore, an interface capable of appropriate energy band bending,
minimal defects, and good contacts is the key issue for obtaining
high-performing and stable PSCs. Herein, we present an innovative
interface engineering approach employing an ortho-squaraine derivative
with zwitterionic resonance structure, which can change the charge
state of the perovskite surface to tune the energy level structure
and can form π–π stacking with the hole-transporting
material to shorten the carrier transmission distance and facilitate
charge transfer. By the synergistic action of the double functionalization,
the PSCs containing 3,4-Bis(4-bromophenyl)cyclobut-3-ene-1,2-dione
achieved power conversion efficiency (PCE) of 23.82%, and the stability
of the unencapsulated devices are greatly improved. For perovskite
interfacial engineering, use of the resonant squaraine zwitterion
is a promising chemical design element to enhance PSCs’ efficiency
and stability.
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