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The emergence of polymerized small molecule acceptors (PSMAs) has significantly improved the performance of all-polymer solar cells (all-PSCs). However, the pace of device engineering lacks behind that of materials development, so that a majority of the PSMAs have not fulfilled their potentials. Furthermore, most high-performance all-PSCs rely on the use of chloroform as the processing solvent. For instance, the recent high-performance PSMA, named PJ1-gamma, with high LUMO, and HOMO levels, could only achieve a PCE of 16.1% with a high-energy-level donor (JD40) using chloroform. Herein, we present a methodology combining sequential processing (SqP) with the addition of 0.5%wt PC71BM as a solid additive (SA) to achieve an impressive efficiency of 18.0% for all-PSCs processed from toluene, an aromatic hydrocarbon solvent. Compared to the conventional blend-casting (BC) method whose best efficiency (16.7%) could only be achieved using chloroform, the SqP method significantly boosted the device efficiency using toluene as the processing solvent. In addition, the donor we employ is the classic PM6 that has deeper energy levels than JD40, which provides low energy loss for the device. We compare the results with another PSMA (PYF-T-o) with the same method. Finally, an improved photostability of the SqP devices with the incorporation of SA is demonstrated.

All-polymer solar cells (all-PSCs) have promising potential for industrial production due to their superior stability. Recently, the widespread application of the polymerized small molecule acceptor (PSMA) has led to a surge in the efficiency of all-PSCs. However, the high efficiencies of these devices generally rely on the use of the highly volatile solvent, chloroform (CF). Furthermore, the molecular weights of PSMA are lower than polymer donors, yet their crystallinity is weaker than typical small molecules, making most PSMA-based all-PSCs suffer from low electron mobility. To improve device performance and facilitate large scale production of all-PSCs, it is necessary to enhance electron mobility and avoid the use of CF. This paper investigates the use of sequential processing (SqP) for active layer preparation using toluene as the solvent to address these issues. This work reports 18.1% efficient all-PSC devices, which is the highest efficiency of all-PSCs prepared using non-halogen solvents. This work systematically compares the conventional blend-casting method with the SqP method using PM6 as the donor and PY-V-& gamma; and PJ1-& gamma; as the acceptors, and compares the performance of binary and ternary blends in both methods. Finally, this work measures the device stability and finds that SqP can significantly improve the photostability of the device.

Polymer acceptors based on the polymerization of small-molecule acceptor (PSMAs) have developed rapidly in recent years. All-polymer solar cells (all-PSCs) composed of PSMAs and polymer donors not only retain the excellent mechanical properties, but also have better morphological properties than traditional polymer acceptors such as N2200. However, since PSMAs are generally not highly polymerized, their electron mobilities are generally lower than the hole mobilities of the high-molecular-weight polymer donors they are used with. In this work, we apply the sequential processing (SqP) method and use toluene as the processing solvent to prepare PSMA-based all-PSCs, which effectively improves the electron mobility and shows much higher efficiency (15.8 %) than the SqP device prepared from chloroform (13.9 %) – the conventional solvent used for high-performance PSMAs. Not only that, the efficiency of the toluene-processed SqP device is also higher than that of the device prepared by the traditional blending-casting (BC) method (14.2 %). In addition, for the first time, we reveal the film formation process of all-polymer active layers prepared by the SqP method using the in situ UV-Vis absorption technique, and investigate the vertical phase separation and the rate of exciton generation across the device using film-depth-dependent absorption spectroscopy, which systematically explained the effect of increased mobility on device parameters. This methodology is applied in two different all-polymer systems, namely, PM6:PYF-T-o and PM6:PY-IT, and both systems manifest the same conclusion. © 2022

In this work, we apply the sequential processing (SqP) method to address the relatively low electron mobility in recent all-polymer solar cells (all-PSCs) based on the polymerized small-molecule acceptor (PSMA). Compared to the blend-casting (BC) method, all-PSCs composed of PM6/PY-IT via the SqP method show boosted electron mobility and a more balanced charge carrier transport, which increases the FF of the SqP device and compensates for the short-circuit current loss, rendering comparable overall performance with the BC device. Through film-depth-dependent light absorption spectroscopy, we analyze the sub-layer absorption and exciton generation rate in the vertical direction of the device, and discuss the effect of the increased electron mobility on device performance, accordingly.

We report a study of enhancing the magnetic ordering in a model magnetically doped topological insulator (TI), Bi[subscript 2–x]Cr[subscript x]Se[subscript 3], via the proximity effect using a high-T[subscript C] ferrimagnetic insulator Y[subscript 3]Fe[subscript 5]O[subscript 12]. The FMI provides the TI with a source of exchange interaction yet without removing the nontrivial surface state. By performing the elemental specific X-ray magnetic circular dichroism (XMCD) measurements, we have unequivocally observed an enhanced T[subscript C] of 50 K in this magnetically doped TI/FMI heterostructure. We have also found a larger (6.6 nm at 30 K) but faster decreasing (by 80% from 30 to 50 K) penetration depth compared to that of diluted ferromagnetic semiconductors (DMSs), which could indicate a novel mechanism for the interaction between FMIs and the nontrivial TIs surface., State Key Programme for Basic Research of China (Grant 2014CB921101), National Natural Science Foundation (China) (Grant 61274102), Science and Technology Facilities Council (Great Britain), United States. Defense Advanced Research Projects Agency. Meso Program (Contract N66001-12-1-4034), United States. Defense Advanced Research Projects Agency. Meso Program (Contract N66001-11-1-4105)

We report a study of enhancing the magnetic ordering in a model magnetically doped topological insulator (TI), Bi[subscript 2–x]Cr[subscript x]Se[subscript 3], via the proximity effect using a high-T[subscript C] ferrimagnetic insulator Y[subscript 3]Fe[subscript 5]O[subscript 12]. The FMI provides the TI with a source of exchange interaction yet without removing the nontrivial surface state. By performing the elemental specific X-ray magnetic circular dichroism (XMCD) measurements, we have unequivocally observed an enhanced T[subscript C] of 50 K in this magnetically doped TI/FMI heterostructure. We have also found a larger (6.6 nm at 30 K) but faster decreasing (by 80% from 30 to 50 K) penetration depth compared to that of diluted ferromagnetic semiconductors (DMSs), which could indicate a novel mechanism for the interaction between FMIs and the nontrivial TIs surface., State Key Programme for Basic Research of China (Grant 2014CB921101), National Natural Science Foundation (China) (Grant 61274102), Science and Technology Facilities Council (Great Britain), United States. Defense Advanced Research Projects Agency. Meso Program (Contract N66001-12-1-4034), United States. Defense Advanced Research Projects Agency. Meso Program (Contract N66001-11-1-4105)