Tunable Donor Aggregation Dominance in a Ternary Matrix of All-Polymer Blends with Improved Efficiency and Stability.

Using two structurally similar polymer acceptors in constructing high-efficiency ternary all-polymer solar cells is a widely acknowledged strategy; however, the focus thus far has not been on how polymer acceptor(s) would tune the aggregation of polymer donors, and furthermore film morphology and device performance (efficiency and stability). Herein, it is reported that matching of the celebrity acceptor PY-IT and the donor PBQx-TCl results in enhanced H-aggregation in PBQx-TCl, which can be finely tuned by controlling the amount of the second acceptor PY-IV. Consequently, the efficiency-optimized PY-IV weight ratio (0.2/1.2) leads to a state-of-the-art power conversion efficiency of 18.81%, wherein light-illuminated operational stability is also enhanced along with well-protected thermal stability. Such enhancements in the efficiency and operational and thermal stabilities of solar cells can be attributed to morphology optimization and the desired glass transition temperature of the target active layer based on comprehensive characterization. In addition to being a high-power conversion efficiency case for all-polymer solar cells, these enhancements are also a successful attempt for using combined acceptors to tune donor aggregation toward optimal morphology, which provides a theoretical basis for the construction of other types of organic photovoltaics beyond all-polymer solar cells.

Printing High-Efficiency Perovskite Solar Cells in High-Humidity Ambient Environment-An In Situ Guided Investigation.

Extensive studies are conducted on perovskite solar cells (PSCs) with significant performance advances (mainly spin coating techniques), which have encouraged recent efforts on scalable coating techniques for the manufacture of PSCs. However, devices fabricated by blade coating techniques are inferior to state-of-the-art spin-coated devices because the power conversion efficiency (PCE) is highly dependent on the morphology and crystallization kinetics in the controlled environment and the delicate solvent system engineering. In this study, based on the widely studied perovskite solution system dimethylformamide-dimethyl sulfoxide, air-knife-assisted ambient fabrication of PSCs at a high relative humidity of 55 ± 5% is reported. In-depth time-resolved UV-vis spectrometry is carried out to investigate the impact of solvent removal and crystallization rate, which are critical factors influencing the crystallization kinetics and morphology because of adventitious moisture. UV-vis spectrometry enables accurate determination of the thickness of the wet precursor film. Anti-solvent-free, high-humidity ambient coatings of hysteresis-free PSCs with PCEs of 21.1% and 18.0% are demonstrated for 0.06 and 1 cm2 devices, respectively. These PSCs exhibit comparable stability to those fabricated in a glovebox, thus demonstrating their high potential.