title: Enhanced performance of PTB7:PC₇₁BM solar cells via different morphologies of gold nanoparticles.
abstract: The effects of gold nanoparticles (AuNPs) incorporated in the hole transporting layer (HTL) of poly[[4,8-bis[(2-ethylhexyl)oxy] benzo[1,2-b:4,5-b'] dithiophene-2, 6-diyl] [3-fluoro-2-[(2-ethylhexy)carbonyl]thieno[3,4-b]thiophened iyl]] (PTB7): [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) based solar cells are being systematically investigated in terms of the optical properties, electrical properties, and photovoltaic performance. The impacts of AuNPs on the optical response of the devices are modeled by finite-difference time-domain (FDTD) simulation. The size of the AuNPs used in this work is around 50-70 nm, so that 10-20 nm penetrated from the HTL into the active layer. We found that the power conversion efficiencies (PCEs) of the devices with AuNPs are significantly enhanced from 7.5%, for the control device, to 8.0%, 8.1%, and 8.2% for Au nanosphere-, nanorod-, and nanocube-incorporated devices, respectively. Among the photovoltaic parameters of the AuNP devices, the short circuit current density (JSC) exhibits the largest improvement, which can be attributed to the improved optical properties of the devices. On the basis of the calculation results, the scattering cross section for the samples in the presence of AuNPs can be enhanced by a factor of ∼10(10)-10(13) and Au nanocubes exhibit superior scattering cross section compared to the Au nanospheres and nanorods with the same linear dimension. From the experimental impedance spectroscopy results, we found that the addition of AuNPs had little effect on the electrical properties of the device. The device performance is also found to be sensitive to the concentration and morphology of the AuNPs.
authors.affiliation: Department of Electronic and Information Engineering, The Hong Kong Polytechnic University , Hung Hom, Hong Kong.
authors.forename: Annie
authors.initials: A
authors.lastname: Ng
authors.forename: Wai Kin
authors.initials: WK
authors.lastname: Yiu
authors.forename: Yishu
authors.initials: Y
authors.lastname: Foo
authors.forename: Qian
authors.initials: Q
authors.lastname: Shen
authors.forename: Amina
authors.initials: A
authors.lastname: Bejaoui
authors.forename: Yiying
authors.initials: Y
authors.lastname: Zhao
authors.forename: Huseyin Cem
authors.initials: HC
authors.lastname: Gokkaya
authors.forename: Aleksandra B
authors.initials: AB
authors.lastname: Djurišić
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: Zapien
authors.forename: Wai Kin
authors.initials: WK
authors.lastname: Chan
authors.forename: Charles
authors.initials: C
authors.lastname: Surya
keywords: absorption; finite-difference time-domain; gold nanoparticles; plasmonic effect; polymer solar cells; scattering