title: Record high efficiency single-walled carbon nanotube/silicon p-n junction solar cells.
abstract: Carrier transport characteristics in high-efficiency single-walled carbon nanotubes (SWNTs)/silicon (Si) hybrid solar cells are presented. The solar cells were fabricated by depositing intrinsic p-type SWNT thin-films on n-type Si wafers without involving any high-temperature process for p-n junction formation. The optimized cells showed a device ideality factor close to unity and a record-high power-conversion-efficiency of >11%. By investigating the dark forward current density characteristics with varying temperature, we have identified that the temperature-dependent current rectification originates from the thermally activated band-to-band transition of carriers in Si, and the role of the SWNT thin films is to establish a built-in potential for carrier separation/collection. We have also established that the dominant carrier transport mechanism is diffusion, with minimal interface recombination. This is further supported by the observation of a long minority carrier lifetime of ~34 μs, determined by the transient recovery method. This study suggests that these hybrid solar cells operate in the same manner as single crystalline p-n homojunction Si solar cells.
authors.affiliation: Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520, USA. yeonwoong.jung@yale.edu
authors.forename: Yeonwoong
authors.initials: Y
authors.lastname: Jung
authors.forename: Xiaokai
authors.initials: X
authors.lastname: Li
authors.forename: Nitin K
authors.initials: NK
authors.lastname: Rajan
authors.forename: André D
authors.initials: AD
authors.lastname: Taylor
authors.forename: Mark A
authors.initials: MA
authors.lastname: Reed