Abstract
A major challenge for organic solar cell (OSC) research is how to minimize the tradeoff between voltage loss and charge generation. In early 2019, we reported a non-fullerene acceptor (named Y6) that can simultaneously achieve high external quantum efficiency and low voltage loss for OSC. Here, we use a combination of experimental and theoretical modeling to reveal the structure-property-performance relationships of this state-of-the-art OSC system. We find that the distinctive π–π molecular packing of Y6 not only exists in molecular single crystals but also in thin films. Importantly, such molecular packing leads to (i) the formation of delocalized and emissive excitons that enable small non-radiative voltage loss, and (ii) delocalization of electron wavefunctions at donor/acceptor interfaces that significantly reduces the Coulomb attraction between interfacial electron-hole pairs. These properties are critical in enabling highly efficient charge generation in OSC systems with negligible donor-acceptor energy offset.
Highlights
A major challenge for organic solar cell (OSC) research is how to minimize the tradeoff between voltage loss and charge generation
We find that the distinctive π-π molecular packings of the Y6 molecules exist in the single crystal and the spin-coated films, which facilitates: (i) the formation of delocalized and emissive excitons that can be effectively populated from the charge transfer (CT) state, leading to small non-radiative voltage loss; (ii) efficient delocalization of electron wavefunctions at the donor/acceptor interfaces, which significantly reduces the interfacial Coulomb attraction of the CT state
In summary, we have reported a systematic study combining both experimental and theoretical modeling analyses to establish structure-property-performance relationships in state-of-the-art OSCs based on an efficient non-fullerene acceptor, Y6
Summary
A major challenge for organic solar cell (OSC) research is how to minimize the tradeoff between voltage loss and charge generation. PBDB-T-2F:Y6 based OSCs show an EQE onset extending to 920 nm, and it is very rare for such a low-gap system to simultaneously achieve a low ΔVOC,nr and an extremely high EQE (Supplementary Fig. 4), which were found in other reports based on Y6 and Y6 derivative systems[23,24,25] This material design have triggered extensive investigations over the past year aiming to further improve the performance of OSCs by fine tuning the Y6-based acceptor molecular structures[26,27,28], introducing ternary blend systems[29,30,31] and using new donor polymers[32,33], leading to further increase in the device efficiency. To better evaluate the structure-property relationship of the OSCs, the molecular packing of the acceptor in the BHJ film and how such packing can affect the electronic processes at the acceptor/donor interface need to be studied in order to provide better understanding on the origin of the high-performance devices
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
