“N‐π‐N” Type Oligomeric Acceptor Achieves an OPV Efficiency of 18.19% with Low Energy Loss and Excellent Stability

Abstract

A novel “N‐ π ‐N” type oligomeric acceptor of 2BTP‐2F‐T, constructed by two small non‐fullerene acceptor (NFA) units linked with a thiophene π bridge is reported. The 2BTP‐2F‐T not only combines the advantages of small NFA and polymeric acceptors (PYF‐T‐ o ) with similar units but also exhibits superior characteristics of high absorption coefficient and high electron moblity( µ e) ) with less dependence on molecular packing. Using PM6 as the donor, a remarkable efficiency of 18.19% is obtained with an open circuit ( V oc ) of 0.911 V, short current circuit ( J sc ) of 25.50 mA cm −2 , and fill factor (FF) of 78.3%, which is much better than that of the corresponding monomer (16.54%) and PYF‐T‐ o (15.8%) based devices. The much‐improved efficiency results from two aspects: 1) an enhanced FF due to the largely improved µ e and well‐controlled morphology ; 2) a higher value of ( J sc × V oc ) due to its higher absorption coefficient and efficient charge generation at a similar low energy loss. Furthermore, the PM6/2BTP‐2F‐T device possesses the longest T 80 lifetime to light‐soaking and comparable high thermal stability with PM6/PYF‐T‐ o . The results indicate that the “N‐ π ‐N” type oligomeric acceptor has a great application prospect due to its superior high efficiency and improved stability in organic solar cells.

Linker Engineering of Dimerized Small Molecule Acceptors for Highly Efficient and Stable Organic Solar Cells

“…Dimerized small-molecule acceptors (DSMAs) are promising alternatives because they can leverage the advantages of both SMA and PSMA systems. , DSMAs can demonstrate higher electron mobility than PSMAs because their discrete molecular structures enable more-strongly developed crystalline structures and intermolecular assembly as well as low batch-to-batch variation. In addition, because DSMAs have a larger molecular size than their constituent SMAs, they have a significantly higher onset temperature (i.e., T g ) for molecular movement and slower diffusion kinetics, which can lead to OSCs with enhanced thermal and morphological stability. , However, the PCEs of DSMA-based OSCs are still lower than those of state-of-the-art SMA- and PSMA-based OSCs, thereby necessitating the further development of DSMAs. In particular, it is important to develop efficient DSMAs so that their electron mobilities are comparable to those of SMAs (>10 –3 to 10 –4 cm 2 V –1 s –1 ).…”

Y-Series-Based Polymer Acceptors for High-Performance All-Polymer Solar Cells in Binary and Non-binary Systems

“…Highly branched polymer structures have been developed to realize 3D networks with good crystallinity and solubility . Besides, by connecting two SMAs through a π-bridge, the design of A-π-A (N-π-N) quasi-macromolecule acceptors , increases the conjugation length for more electron delocalization while still maintaining definite molecular structures with fewer chain entanglements. Consequently, it is possible to simultaneously achieve the high device performance of SMA-based PSCs and the excellent device stability observed with all-PSCs. As previous research has demonstrated that the high PCE values in both PSCs with SMAs (>19%) and polymer acceptors (>17%) were obtained with ternary systems, more effort can be devoted to this category.…”

Tethered Small‐Molecule Acceptors Simultaneously Enhance the Efficiency and Stability of Polymer Solar Cells

“…Inspired by the inherent high stability of PSMAs, the use of two or three conjugated segments of PSMAs, to develop SMA-based oligomers characterized with a strictly uniform molecular structure, offers a promising strategy. [39][40][41][42] However, the construction of such molecular fragments usually has a low yield (typical 30-40%) due to the difficulty in the synthesis of the key intermediate (monobrominated SMA), which ultimately increases their production cost. A heavy reliance on toxic tin compounds and noble metal catalysts to couple the SMA units also causes environmental concerns within a commercial setting.…”