The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/solr.202200645.

Herein, a string of quinoxaline-based D–A-type polymers possessing either electron-withdrawing or electron-donating groups were developed to explore their impact on the photovoltaic efficiency of the polymers. Once the reference polymer PBF-CF3Qx was prepared, extra fluorine atoms and methoxy units were selectively added on the 6,7-positions of the quinoxaline unit of the PBF-CF3Qx reference to provide two objective polymers, PBF-CF3QxF and PBF-CF3QxM, respectively. Owing to the significant influence of the existing electron-withdrawing or electron-donating substituents, each polymer displayed considerably discernible optical, electrochemical, and morphological features. Moreover, the conventional nonfullerene photovoltaic devices based on PBF-CF3QxF and PBF-CF3QxM exhibited superior power conversion efficiencies of 11.37 and 11.18%, respectively, compared to the device based on the PBF-CF3Qx reference 6.96%). These results emphasize the significance of electron-withdrawing and electron-donating substituents in quinoxaline-based polymers for controlling their intrinsic and photovoltaic attributes.

Indolocarbazole (Ic) conjugated small molecular electrolytes (CSMEs) with different amine side chains are synthesized and applied to the formation of an electron transporting layer (ETL), via spontaneous phase separation, in bulk heterojunction (BHJ) polymer solar cells (PSCs). The self-assembled bilayer with a BHJ-active layer on top and a CSME layer at the bottom is generated by a single coating step of one solution of CSME and BHJ-active layer materials, CSME:PTB7-Th:PC71BM. The location of the CSME layer is confirmed by time-of-flight secondary ion mass spectroscopy. The CSME layer plays the role of an ETL, which reduces the work function of indium tin oxide (ITO) effectively and leads to high power conversion efficiency (PCE) of the CSME-modified PSC. We also use X-ray photoelectron spectroscopy to test the relative intensity of hydrogen bonds between the CSME and ITO. With the increased relative intensity of hydrogen bonds between the CSME and ITO, more effective spontaneous phase separation of the CSME/BHJ bilayer can be formed to generate the CSME layer on top of ITO, and the photovoltaic performance of the PSC enhanced. Out of the synthesized series of CSMEs (IcL4N, IcL6N, IcL8N, IcL10N, and IcB8N), the IcB8N-based device shows the highest relative intensity of hydrogen bonding and the highest PCE with a value of 7.09% without using any other ETL materials, which is the highest PCE value without using any other ETL in a separate processing step, in I-PSCs utilizing PTB7-Th:PC71BM.

Here, the potential of pyrrolo­[3,4-c]­pyrrole-1,3­(2H,5H)-dione-based polymers, namely, poly­[4,8-bis­(5-(2-ethylhexyl)­thiophen-2-yl)­benzo­[1,2-b:4,5-b′]­dithiophene-alt-2,5-dioctyl-4,6-di­(thiophen-2-yl)­pyrrolo­[3,4-c]­pyrrole-1,3­(2H,5H)-dione) (PBDPD), is tested as an electron donor in nonfullerene electron acceptor-based organic solar cells (NFA OSCs). Polymer PBDPD shows an intense absorption between 300 and 600 nm with a deeper highest occupied molecular orbital of −5.44 eV. Noticeably, PBDPD displays good complementary absorption and well-matched energy levels with various NFAs. The binary NFA OSCs are fabricated by using PBDPD without any additive or postannealing treatment, providing a maximum power conversion efficiency (PCE) of 11.24% with an impressive open-circuit voltage (V oc) of 1.004 V and a low energy loss (E loss) of 0.496 eV. These results suggest that PBDPD could be a useful candidate for tandem NFA OSCs. Therefore, the tandem NFA OSCs are fabricated using PBDPD with the aim of further maximizing the V oc of the NFA OSCs. The respective tandem NFA OSCs provide an impressive PCE of 15.71% with a greatly improved V oc of 1.73 V. This study suggests that the PD-based polymers are efficient candidates for NFA OSCs, and it opens a new platform for researchers planning to develop efficient wide band-gap polymers for NFA OSCs.

We report the design and synthesis of phenothiazine-based conjugated small-molecular electrolytes as an ETL that could be applied to provide spontaneous phase separation, to reduce the number of steps required for device fabrication.