Application of hole-transporting materials as the interlayer in graphene oxide/single-wall carbon nanotube silicon heterojunction solar cells

Solid-state hole-transporting materials, including the traditional poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), and recently developed 4,4′-(naphthalene-2,6-diyl)bis(N,N-bis(4-methoxyphenyl)aniline) (NAP) and (E)-4′,4‴-(ethene-1,2-diyl)bis(N,N-bis(4-methoxyphenyl)-[1″,1‴-biphenyl]-4-amine) (BPV), have been applied as a hole-transporting interlayer (HTL) for graphene oxide/single-walled carbon nanotube-silicon (GOCNT/Si) heterojunction solar cells, forming a GOCNT/HTL/Si architecture. The influence of the thickness of the HTL has been studied. A new AuCl3 doping process based on bath immersion has been developed and proved to improve the efficiency. With the AuCl3-doped GOCNT electrodes, the efficiency of GOCNT/PEDOT:PSS/Si, GOCNT/NAP/Si, and GOCNT/BPV/Si devices was improved to 12.05±0.21, 10.57±0.37, and 10.68±0.27% respectively. This study reveals that the addition of an HTL is able to dramatically minimise recombination at the heterojunction interface.