Efficient and Stable Planar n-i-p Sb₂Se₃ Solar Cells Enabled by Oriented 1D Trigonal Selenium Structures

Environmentally benign and potentially cost-effective Sb₂Se₃ solar cells have drawn much attention by continuously achieving new efficiency records. This article reports a compatible strategy to enhance the efficiency of planar n-i-p Sb₂Se₃ solar cells through Sb₂Se₃ surface modification and an architecture with oriented 1D van der Waals material, trigonal selenium (t-Se). A seed layer assisted successive close spaced sublimation (CSS) is developed to fabricate highly crystalline Sb₂Se₃ absorbers. It is found that the Sb₂Se₃ absorber exhibits a Se-deficient surface and negative surface band bending. Reactive Se is innovatively introduced to compensate the surface Se deficiency and form an (101) oriented 1D t-Se interlayer. The p-type t-Se layer promotes a favored band alignment and band bending at the Sb₂Se₃/t-Se interface, and functionally works as a surface passivation and hole transport material, which significantly suppresses interface recombination and enhances carrier extraction efficiency. An efficiency of 7.45% is obtained in a planar Sb₂Se₃ solar cell in superstrate n-i-p configuration, which is the highest efficiency for planar Sb₂Se₃ solar cells prepared by CSS. The all-inorganic Sb₂Se₃ solar cell with t-Se shows superb stability, retaining ≈98% of the initial efficiency after 40 days storage in open air without encapsulation.