title: Unsymmetrical Donor-Acceptor-Acceptor-π-Donor Type Benzothiadiazole-Based Small Molecule for a Solution Processed Bulk Heterojunction Organic Solar Cell.
abstract: A D1-A-A'-π-D2 type (D = donor; A = acceptor) unsymmetrical small molecule denoted as BTD3 containing different end group donor moieties has been designed and synthesized for use as a donor in the solution processable bulk heterojunction (BHJ) solar cell. The BTD3 exhibits a low HOMO-LUMO gap of 1.68 eV and deeper HOMO energy level (-5.5 eV). Its LUMO energy level (-3.65 eV) is compatible with the LUMO level of PC71BM to facilitate the electron transfer from BTD3 to PC71BM in the BHJ solar cell. The solution processed BHJ solar cell with optimized BTD3:PC71BM active layer processed with THF solvent exhibited a PCE of 3.15% with Jsc = 7.45 mA/cm(2), Voc = 0.94 V, and FF = 0.45. Moreover, the device with optimized concentration of 3 vol. % 1-chloronaphthalene (CN) additive, i.e., CN/THF, showed significant enhancement in PCE up to 4.61% (Jsc = 9.48 mA/cm(2), Voc = 0.90 V, and FF = 0.54). The improvement in the PCE has been attributed to the appropriate nanoscale phase separation morphology, balance charge transport, and enhancement in the light harvesting ability of the active layer.
authors.affiliation: †Department of Chemistry, Indian Institute of Technology, Indore, Madhya Pradesh 452017, India.
authors.forename: Prabhat
authors.initials: P
authors.lastname: Gautam
authors.affiliation: †Department of Chemistry, Indian Institute of Technology, Indore, Madhya Pradesh 452017, India.
authors.forename: Rajneesh
authors.initials: R
authors.lastname: Misra
authors.affiliation: ‡Department of Electrical Engineering, Vivekanand Institute of Technology, Jagatpura, Jaipur, Rajasthan 302025, India.
authors.forename: Shahbaz A
authors.initials: SA
authors.lastname: Siddiqui
authors.affiliation: §R and D Center for Science and Engineering, JEC Group of Colleges, Jaipur Engineering College Campus, Kukas, Jaipur, Rajasthan 302028, India.
authors.forename: Ganesh D
authors.initials: GD
authors.lastname: Sharma
keywords: bulk heterojunction organic solar cells; power conversion efficiency; solvent additives; unsymmetrical D1−A−A′−π−D2 small molecule