title: Low-Temperature Solution-Processed Thiophene-Sulfur-Doped Planar ZnO Nanorods as Electron-Transporting Layers for Enhanced Performance of Organic Solar Cells.
abstract: 1-D ZnO represents a fascinating class of nanostructures that are significant to optoelectronics. In this work, we investigated the use of an eco-friendly, metal free in situ doping through a pure thiophene-sulfur (S) on low temperature processed (<95 °C) and annealed (<170 °C), planar 1-D ZnO nanorods (ZnRs) spin-coated as a hole-blocking and electron transporting layer (ETL) for inverted organic solar cells (iOSCs). The TEM, HRTEM, XPS, FT-IR, EDS and Raman studies clearly reveal that the thiophene-S (Thi-S) atom is incorporated on planar ZnRs. The investigations in electrical properties suggest the enhancement in conductivity after Thi-S doping on 1-D ZnRs. The iOSCs of poly(3-hexylthiophene-2,5-diyl) and phenyl-C61-butyric acid methyl ester (P3HT: PC60BM) photoactive layer containing thiophene-S doped planar ZnRs (Thi-S-PZnRs) as ETL exhibits power conversion efficiency (PCE) of 3.68% under simulated AM 1.5 G, 100 mW cm-2illumination. The ∼47% enhancement in PCE compared with pristine planar ZnRs (PCE = 2.38%) ETL is attributed to a combination of desirable energy level alignment, morphological modification, increased conductivity and doping effect. The universality of Thi-S-PZnRs ETL is demonstrated by the highest PCE of 8.15% in contrast to 6.50% exhibited by the iOSCs of ZnRs ETL for the photoactive layer comprising of poly[4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b;4,5-b]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)]: phenyl-C71-butyric acid methyl ester (PTB7-Th: PCB71M). This enhancement in PCE is observed to be driven mainly through improved photovoltaic parameters like fill factor (ff) as well as photocurrent density (Jsc), which are assigned to increased conductivity, exciton dissociation, and effective charge extraction, while; better ohmic contact, reduced charge recombination, and low leakage current density resulted in increased Voc.
authors.affiliation: School of Semiconductor and Chemical Engineering, Chonbuk National University , 567 Baekje-daero, Jeonju, 54896, Republic of Korea.
authors.forename: Swapnil B
authors.initials: SB
authors.lastname: Ambade
authors.affiliation: School of Semiconductor and Chemical Engineering, Chonbuk National University , 567 Baekje-daero, Jeonju, 54896, Republic of Korea.
authors.forename: Rohan B
authors.initials: RB
authors.lastname: Ambade
authors.affiliation: School of Semiconductor and Chemical Engineering, Chonbuk National University , 567 Baekje-daero, Jeonju, 54896, Republic of Korea.
authors.forename: Sushil S
authors.initials: SS
authors.lastname: Bagde
authors.affiliation: School of Semiconductor and Chemical Engineering, Chonbuk National University , 567 Baekje-daero, Jeonju, 54896, Republic of Korea.|Division of Advanced Materials, Korea Research Institute of Chemical Technology (KRICT) , 141 Gajeong-ro, Yuseong-gu, Daejeon 34114, Republic of Korea.
authors.forename: Seung Hun
authors.initials: SH
authors.lastname: Eom
authors.affiliation: Centre for Nanomaterials & Energy Devices, School of Physical Sciences, SRTM, University , 431606, Nanded, India.
authors.forename: Rajaram S
authors.initials: RS
authors.lastname: Mane
authors.affiliation: Energy Materials Research Centre, Korea Research Institute of Chemical Technology , Daejeon, Korea.
authors.forename: Won Suk
authors.initials: WS
authors.lastname: Shin
authors.affiliation: School of Semiconductor and Chemical Engineering, Chonbuk National University , 567 Baekje-daero, Jeonju, 54896, Republic of Korea.
authors.forename: Soo-Hyoung
authors.identifier: http://orcid.org/0000-0002-2730-5723
authors.initials: SH
authors.lastname: Lee
keywords: electron transporting layer; inverted organic solar cells; morphology; thiophene-sulfur doped-ZnO; work function