title: Photovoltaic devices and characterization of a dodecyloxybenzothiadiazole-based copolymer.
abstract: A conjugated copolymer based on alternating benzo[1,2-b;3,4-b']dithiophene (BDT) donor and dodecyloxy substituted benzo[c][1,2,5]thiadiazole (ABT) acceptor units was prepared for application in organic solar cells. A power conversion efficiency (PCE) of ~3% with a short-circuit current (Jsc) of 7.63 mA cm(-2), an open-circuit voltage (Voc) of 0.71 V and a fill-factor (FF) of 53.74% was obtained under the illumination of AM 1.5 solar irradiation (100 mW cm(-2)). Photovoltaic devices and their transient properties with a blend of the copolymer and the [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) at different ratios were studied using transient photovoltage (TPV), transient photocurrent (TPC) and atomic force microscopy (AFM) measurements. From the TPV and TPC measurements, the charge recombination times (τn) were found to be 21.1 μs, 12.6 μs and 10.5 μs, and the charge transport times (τd) were 1316 ns, 422 ns and 707 ns for the 1 : 0.5, 1 : 1 and 1 : 2 donor/acceptor (D/A) ratios, respectively. The 1 : 1 D/A ratio showed the shortest charge transport time (τd) and the longest charge diffusion length (Ln) according to L(n) [proportionality] √[τ(n)/τ(d)], leading to the highest device performance among the three ratios.
authors.affiliation: Center for Advanced Photovoltaics, Department of Electrical Engineering, South Dakota State University, Brookings, SD 57007, USA.
authors.forename: Purna P
authors.initials: PP
authors.lastname: Maharjan
authors.forename: Qiliang
authors.initials: Q
authors.lastname: Chen
authors.forename: Lianjie
authors.initials: L
authors.lastname: Zhang
authors.forename: Olusegun
authors.initials: O
authors.lastname: Adebanjo
authors.forename: Nirmal
authors.initials: N
authors.lastname: Adhikari
authors.forename: Swaminathan
authors.initials: S
authors.lastname: Venkatesan
authors.forename: Prajwal
authors.initials: P
authors.lastname: Adhikary
authors.forename: Bjorn
authors.initials: B
authors.lastname: Vaagensmith
authors.forename: Qiquan
authors.initials: Q
authors.lastname: Qiao