Precisely Controlling Polymer Acceptors with Weak Intramolecular Charge Transfer Effect and Superior Coplanarity for Efficient Indoor All-Polymer Solar Cells with over 27% Efficiency.

Indoor photovoltaics (IPVs) are garnering increasing attention from both the academic and industrial communities due to the pressing demand of the ecosystem of Internet-of-Things. All-polymer solar cells (all-PSCs), emerging as a sub-type of organic photovoltaics, with the merits of great film-forming properties, remarkable morphological and light stability, hold great promise to simultaneously achieve high efficiency and long-term operation in IPV's application. However, the dearth of polymer acceptors with medium-bandgap has impeded the rapid development of indoor all-PSCs. Herein, a highly efficient medium-bandgap polymer acceptor (PYFO-V) is reported through the synergistic effects of side chain engineering and linkage modulation and applied for indoor all-PSCs operation. As a result, the PM6:PYFO-V-based indoor all-PSC yields the highest efficiency of 27.1% under LED light condition, marking the highest value for reported binary indoor all-PSCs to date. More importantly, the blade-coated devices using non-halogenated solvent (o-xylene) maintain an efficiency of over 23%, demonstrating the potential for industry-scale fabrication. This work not only highlights the importance of fine-tuning intramolecular charge transfer effect and intrachain coplanarity in developing high-performance medium-bandgap polymer acceptors but also provides a highly efficient strategy for indoor all-PSC application.

Improved photovoltaic performance and robustness of all-polymer solar cells enabled by a polyfullerene guest acceptor.

Fullerene acceptors typically possess excellent electron-transporting properties and can work as guest components in ternary organic solar cells to enhance the charge extraction and efficiencies. However, conventional fullerene small molecules typically suffer from undesirable segregation and dimerization, thus limiting their applications in organic solar cells. Herein we report the use of a poly(fullerene-alt-xylene) acceptor (PFBO-C12) as guest component enables a significant efficiency increase from 16.9% for binary cells to 18.0% for ternary all-polymer solar cells. Ultrafast optic and optoelectronic studies unveil that PFBO-C12 can facilitate hole transfer and suppress charge recombination. Morphological investigations show that the ternary blends maintain a favorable morphology with high crystallinity and smaller domain size. Meanwhile, the introduction of PFBO-C12 reduces voltage loss and enables all-polymer solar cells with excellent light stability and mechanical durability in flexible devices. This work demonstrates that introducing polyfullerenes as guest components is an effective approach to achieving highly efficient ternary all-polymer solar cells with good stability and mechanical robustness.