Tuning photovoltaic parameters in polymer solar cells through side-chain modification of donor polymer based on cyclopenta[c]thiophene-4,6(5H)-dione

• Published in: Organic electronics 2024-06, Vol.129, p.107059, Article 107059
• Main Authors: Son, Dong Hwan, Nasrun, Rahmatia Fitri Binti, Kim, Joo Hyun
• Format: Article
• Language: English
• Subjects: Non-fullerene; Photoactive layer; Polymer donor; Polymer solar cell; Thiophene-dione
• ISSN: 1566-1199; 1878-5530
• DOI: 10.1016/j.orgel.2024.107059

Conjugated polymers were developed by using thiophene-dione derivatives named DEHOB-BDTF and DBOOB-BDTF. The polymers have a combination of electron donor (D) and electron acceptor (A), in which 5-(3,4-bis(((2-ethylhexyl)oxy)benzylidene)-1,3-dibromo-4H-cyclopenta[c]thiophene-4,6(5H)-dione (DEHOB) or 5-(3,4-bis((2-butyloctyl)oxy)benzylidene)-1,3-dibromo-4H-cyclopenta[c]thiophene-4,6(5H)-dione (DBOOB) serves as the electron acceptor units. The alkoxy chain shows strong electron-donating properties due to conjugation effects while longer alkoxy chain increases the solubility. Non-fullerene PSCs are fabricated with an ITO/ZnO/polymer: Y6BO/MoO3/Ag structure in which Y6BO is used as an electron acceptor. The performance of the device by using DEHOB-BDTF is accomplished up to 8.49 % (an open-circuit voltage of 0.85 V and a short-circuit current density of 20.1 mA/cm2). Furthermore, the longer alkoxy chain length enhances solubility making a well-ordering in DBOOB and reaching the fill factor of 54.2 %, due to the extended alkoxy chain can improve the miscibility in the blend. The effect of side-chain modification of conjugated polymers for organic solar cells as a donor polymer was investigated. We found that the extended alkoxy chain can increase the packing of the intermolecular section, but the extended alkoxy chain polymer can reduce the active layer ordering. Therefore, the device based on shorter alkoxy chain polymers has higher Jsc. [Display omitted] •A series of polymers based on thiophene-dione derivatives is synthesized.•Thiophene-dione derivatives with various alkoxy chains are used as donor polymers.•Shorter alkoxy chain improves current density due to the broad absorption spectra.•The improved solubility by alkoxy chain extension results in enhanced fill factor.