Abstract
Silicon solar cells have the advantages of high efficiency and abundant resources on earth.And organic solar cells can be fabricated in low temperature,low-cost solution processes and also has roll-to-roll scalability.Combining the advantages of these two material systems,hybrid solar cells based on organic conjugated polymers and inorganic silicon is a promising alternative to simplify the fabrication processes and reduce the cost,while maintaining a high PCE. In this study,we introduce a co-solvent method to dope a wide band gap poly(9,9-dioctyfluorenyl-2,7-diyl) (PFO) fluorescent polymers with a very efficient electron acceptor tetrafluorotetracyanoquinodimethane(F4TCNQ).The p-doping layer was deposited onto and between 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane(TAPC)layer and SiNWs by the solution processing method in order to form a recombination layer and lower Fermi level of fluorescent polymers. Furthermore,Ultraviolet Photoelectron spectroscopy (UPS) and X-ray Photoemission spectroscopy (XPS) confirms that F4TCNQ is spatially graded doping via vertical phase separation in this p-type doping layer.The nearer to SiNWs,the more F4TCNQ is doped, which let p-type layers become more p-type. The power conversion efficiency reaches a record 13.6%, which is largely ascribed to the band bending between n-type silicon and p-doping layer interface.Consequently,holes can conduct to electrodes more easily by lowering energy barriers,which boost the open-circuit voltage and fill factor.