An Asymmetric Coumarin-Anthracene Conjugate as Efficient Fullerene-Free Acceptor for Organic Solar Cells.

Asymmetric wide-band gap fullerene-free acceptors (FFAs) play a crucial role in organic solar cells (OSCs). Here, we designed and synthesized a simple asymmetric coumarin-anthracene conjugate named CA-CN with optical band gap of 2.1 eV in a single-step condensation reaction. Single crystal X-ray structure analysis confirms various multiple intermolecular non-covalent interactions. The molecular orbital energy levels of CA-CN estimated from cyclic voltammetry were found to be suitable for its use as an acceptor for OSCs. Binary OSCs fabricated using CA-CN as acceptor and PTB7-Th as the donor achieve a power conversion efficiency (PCE) of 11.13 %. We further demonstrate that the insertion of 20 wt % of CA-CN as a third component in ternary OSCs with PTB7-Th : DICTF as the host material achieved an impressive PCE of 14.91 %, an improvement of ~43 % compared to the PTB7-Th : DICTF binary device (10.38 %). Importantly, the ternary blend enhances the absorption coverage from 400 to 800 nm and improves the morphology of the active layer. The findings highlight the efficacy of an asymmetric design approach for FFAs, which paves the way for developing high-efficiency OSCs at low cost.

Halogenation Strategy: Simple Wide Band Gap Nonfullerene Acceptors with the BODIPY-Thiophene-Backboned Polymer Donor for Enhanced Outdoor and Indoor Photovoltaics.

Researchers have been motivated to develop photovoltaic systems that can efficiently convert artificial light into power with the growing use of indoor electrical devices for the Internet of Things. Understanding the impact of molecular design strategies involving morphological optimization through the terminal group of the non-fullerene acceptors (NFAs) is crucial. This is critically important to enhancing the photovoltaic efficiency of organic photovoltaic devices under diverse irradiation conditions. Halogenation of terminal groups proves to be a standout approach for adjusting energy levels, refining light-harvesting capabilities, crystallinity, and bolstering the intermolecular stacking in NFAs. Herein, we have designed two simple NFAs, DICTF-4F and DICTF-4Cl, to explore the dihalogenation (F and Cl) effect on the terminal group on the optical and electrochemical properties. After combining with the BODIPY-thiophene-backboned donor polymer P(BdP-HT), the organic solar cells (OSCs) using an optimized active layer with P(BdP-HT):DICTF-4F and P(BdP-HT):DICTF-4Cl attained a power conversion efficiency (PCE) of about 8.03 and 14.16%, respectively, under 1 sun illumination. Moreover, the OSC-based P(BdP-HT):DICTF-4Cl active layer showed a PCE approaching 24% under 1000 lx indoor conditions.

Simple and Efficient Acceptor-Donor-Acceptor-Type Non-fullerene Acceptors for a BODIPY-Thiophene-Backboned Polymer Donor for High-Performance Indoor Photovoltaics.

Herein, simple acceptor-donor-acceptor (A-D-A)-type small molecules denoted as DICTF and DRCTF with modification in terminal units were synthesized and used as electron acceptors. With the tuning of the electron-withdrawing units in electron acceptors, their photovoltaic properties were investigated when combined with low-band-gap BODIPY-thiophene-backboned donor material, named P(BdP-HT). The P(BdP-HT):DICTF-based organic solar cells (OSCs) displayed excellent efficiency of around 11.94%, which is superior to the P(BdP-HT):DRCTF counterpart (8.78%). Although the open-circuit voltage (VOC) of the P(BdP-HT):DRCTF-based OSC is greater than that for the P(BdP-HT):DICTF counterpart, the rise in the short-circuit current density (JSC) may be attributed to the fact that the P(BdP-HT):DICTF blend displayed impressive panchromatic absorption compared to P(BdP-HT):DRCTF. The improved fill factor (FF) is responsible for the balanced transport of charges in the P(BdP-HT):DICTF-based device. Moreover, the P(BdP-HT):DRCTF- and P(BdP-HT):DICTF-based OSCs showed 17.68 and 21.84%, respectively, under indoor illumination (1000 lx). To the best of our observation, this might be the first report on BODIPY-based donors with power conversion efficiency (PCE) of 21.84% under indoor illumination conditions.