Exploration of promising optical and electronic properties of (non-polymer) small donor molecules for organic solar cells

Muhammad Khalid; Muhammad Usman Khan; Saeed Ahmed; Zahid Shafiq; Mohammed Mujahid Alam; Muhammad Imran; Ataualpa Albert Carmo Braga; Muhammad Safwan Akram

doi:10.1038/s41598-021-01070-3

Exploration of promising optical and electronic properties of (non-polymer) small donor molecules for organic solar cells

Sci Rep. 2021 Nov 2;11(1):21540. doi: 10.1038/s41598-021-01070-3.

Authors

Muhammad Khalid¹, Muhammad Usman Khan², Saeed Ahmed¹, Zahid Shafiq³, Mohammed Mujahid Alam⁴, Muhammad Imran⁴, Ataualpa Albert Carmo Braga⁵, Muhammad Safwan Akram^{6

7}

Affiliations

¹ Department of Chemistry, Khwaja Fareed University of Engineering & Information Technology, Rahim Yar Khan, 64200, Pakistan.
² Department of Chemistry, University of Okara, Okara, 56300, Pakistan. usman.chemistry@gmail.com.
³ Institute of Chemical Sciences, Bahauddin Zakariya University, Multan, 60800, Pakistan. zahidshafiq25@hotmail.com.
⁴ Department of Chemistry, Faculty of Science, King Khalid University, P.O. Box 9004, Abha, 61413, Saudi Arabia.
⁵ Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, Avenida Professor LineuPrestes, 748, São Paulo, 05508-000, Brazil.
⁶ School of Health and Life Sciences, Teesside University, Middlesbrough, TS1 3BA, UK. Safwan.akram@tees.ac.uk.
⁷ National Horizons Centre, Teesside University, Darlington, DL1 1HG, UK. Safwan.akram@tees.ac.uk.

Abstract

Non-fullerene based organic compounds are considered promising materials for the fabrication of modern photovoltaic materials. Non-fullerene-based organic solar cells comprise of good photochemical and thermal stability along with longer device lifetimes as compared to fullerene-based compounds. Five new non-fullerene donor molecules were designed keeping in view the excellent donor properties of 3-bis(4-(2-ethylhexyl)-thiophen-2-yl)-5,7-bis(2ethylhexyl) benzo[1,2-:4,5-c']-dithiophene-4,8-dione thiophene-alkoxy benzene-thiophene indenedione (BDD-IN) by end-capped modifications. Photovoltaic and electronic characteristics of studied molecules were determined by employing density functional theory (DFT) and time dependent density functional theory (TD-DFT). Subsequently, obtained results were compared with the reference molecule BDD-IN. The designed molecules presented lower energy difference (ΔΕ) in the range of 2.17-2.39 eV in comparison to BDD-IN (= 2.72 eV). Moreover, insight from the frontier molecular orbital (FMO) analysis disclosed that central acceptors are responsible for the charge transformation. The designed molecules were found with higher λ_max values and lower transition energies than BDD-IN molecule due to stronger end-capped acceptors. Open circuit voltage (Voc) was observed in the higher range (1.54-1.78 V) in accordance with HOMO_donor-LUMO_PC61BM by designed compounds when compared with BDD-IN (1.28 V). Similarly, lower reorganization energy values were exhibited by the designed compounds in the range of λ_e(0.00285-0.00370 E_h) and λ_h(0.00847-0.00802 E_h) than BDD-IN [λ_e(0.00700 E_h) and λ_h(0.00889 E_h)]. These measurements show that the designed compounds are promising candidates for incorporation into solar cell devices, which would benefit from better hole and electron mobility.