Growing interests have been devoted to the design of polymer acceptors as potential replacement for fullerene derivatives for high-performance all polymer solar cells (all-PSCs). One key factor that is limiting the efficiency of all-PSCs is the low fill factor (FF) (normally <0.65), which is strongly correlated with the mobility and film morphology of polymer:polymer blends. In this work, we find a facile method to modulate the crystallinity of the well-known naphthalene diimide (NDI) based polymer N2200, by replacing a certain amount of bithiophene (2T) units in the N2200 backbone by single thiophene (T) units and synthesizing a series of random polymers PNDI-Tx, where x is the percentage of the single T. The acceptor PNDI-T10 is properly miscible with the low band gap donor polymer PTB7-Th, and the nanostructured blend promotes efficient exciton dissociation and charge transport. Solvent annealing (SA) enables higher hole and electron mobilities, and further suppresses the bimolecular recombination. As expected, the PTB7-Th:PNDI-T10 solar cells attain a high PCE of 7.6%, which is a 2-fold increase compared to that of PTB7-Th:N2200 solar cells. The FF of 0.71 reaches the highest value among all-PSCs to date. Our work demonstrates a rational design for fine-tuned crystallinity of polymer acceptors, and reveals the high potential of all-PSCs through structure and morphology engineering of semicrystalline polymer:polymer blends.

Cesium‐based all‐inorganic perovskite solar cells (PSCs), especially for CsPbI2Br component‐based devices, have attracted increasing attention due to its advantage of superior thermal and phase stability. Since the pioneering study reported in 2016, more than 30 papers have been published, reporting the rapid boost in the power conversion efficiency (PCE) of PSCs to 14.81%. The CsPbI2Br PSC is one of the most remarkable research hotspots in the field of perovskite photovoltaics. In this progress report, the recent advances in CsPbI2Br PSCs are systematically reviewed, which in turn introduces the basic property and stability of active layers, and the performance improvements in these devices. The challenges as well as the possible solutions toward better‐performing CsPbI2Br PSCs are also discussed. The theoretical calculation results point out that there is much room for further device performance enhancement, particularly in open‐circuit voltages. This progress report focuses on CsPbI2Br material properties and summarizes recent strategies to improve the corresponding device's PCE, in order to open new perspectives toward commercial utility of PSCs.

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The aim of this study was to improve the water resistance of a soybean meal-based adhesive with a low-cost lignin-based resin (LR).