Air-stable silicon hybrid solar cells constructed via hydrophobic polymer film

Abstract

Silicon (Si) hybrid solar cells have advantages of solution manufacturing process and the potential for achieving low-cost fabrication compared to crystalline Si solar cells. However, the functional layer prepared by solution method usually absorbs water molecules from the air, posing a challenge to the stability of the device. Here, a PEDOT derivative, PEDOT:A, was in situ prepared through the introduction of a fluoropolymer, yielding a strongly hydrophobic film that was assembled into a PEDOT:A/Si hybrid solar cell. The PEDOT:A/Si hybrid solar cells retained 90% of its initial performance after storage in the air for 300 h, while PEDOT:PSS only retained 60% with identical device structure. Meanwhile, first principles calculations indicate that the binding energy between fluoropolymer and water molecule was 3.48 kJ/mol, whereas the binding energy between PSS and water molecule was −5.76 kJ/mol. Benefiting from the weak interaction between fluoropolymer and water molecule, the contact angle of water on PEDOT:A film was 100.84°. After optimization, PEDOT:A/Si hybrid solar cells with ITO achieved a power conversion efficiency of 6.43%, retained 97% of its initial efficiency after testing under same conditions. The development of air-stable hybrid device technology is promising in opening up practical applications of low-cost Si based solar cells.