Highly efficient halogen-free rigid and flexible binary organic solar cells using new solid indacene additive

Flexible Organic solar cells (OSCs) have garnered widespread attention due to the increased popularity of wearable electronic devices. To enhance the efficiency and stability of the device we have prepared (2E,2′E)-3,3'-(4,4,9,9-tetrahexadecyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b'] dithiophene-2,7-diyl)bis(2-cyanoacrylic acid) (IDT) based dopant by reacting the aldehyde precursor with cyanoacetic acid in the presence of piperdine. Here, we investigate the effect of IDT on the performance of OSCs by adding IDT to star active layers PM6:Y6 and PM6:BTP-eC9 to improve OSCs' performance through morphology optimization. The addition of 5 wt% IDT significantly improved the device performance, achieving a remarkable PCE of 16.08 % for PM6:Y6 devices. The charge transport and recombination dynamics analysis showed that the appropriate concentration of IDT can provide better channels for carrier transport, promoting effective charge generation and extraction in OSCs. It is observed that the addition of IDT promotes effective generation and dissociation of excitons, thus improving OSC performance. The flexible ITO-free OSC was fabricated using PM6:Y6:IDT as the active layer film, achieving a high PCE of 12.59 % with V_OC, J_SC, and FF of 0.83 V, 23.21 mA/cm² and 68.63 %, respectively. Hence, the findings indicate a reliable approach which could potentially deliver rigid and flexible OSCs with excellent performance and commercial viability.