Importance of High‐Electron Mobility in Polymer Acceptors for Efficient All‐Polymer Solar Cells: Combined Engineering of Backbone Building Unit and Regioregularity

Abstract

The charge transport ability of polymer acceptors (P A s) is crucial for achieving high power conversion efficiencies (PCEs) of all-polymer solar cells (all-PSCs). However, the electron mobilities (μ e s) of most P A s are inferior to those of their small molecule acceptor (SMA) counterparts. Herein, the authors design a new series of the polymerized SMA-based P A s ( Y5-A-B), where the donating moiety (A = selenophene (Se)/biselenophene (BiSe)) and the backbone regioregularity (B = In/Mix/Out) are 2D controlled, for enhancing both the μ e and PCEs. Interestingly, the effects of regioisomers on the μ e and all-PSC performance are the opposite depending on the donating unit. For the Y5-Se-based P A s, the PCEs increase in order of Out (7.52%) < Mix (9.33%) < In (13.38%). In contrast, for the Y5-BiSe-based P A s, the PCEs decrease in order of Out (10.67%) > Mix (9.58%) > In (8.52%). These opposite trends in each series originate from the different planarity and intermolecular assembly of P A s depending on the regioregularity. Thus, the Y5-Se-In blend exhibits the highest μ e and achieves the highest PCE (13.38%) among the all-PSCs in this study. Therefore, the authors report the importance of simultaneous engineering of the backbone building unit and regioregularity to realize high-mobility P A and highly efficient all-PSCs.

Isogenous Asymmetric–Symmetric Acceptors Enable Efficient Ternary Organic Solar Cells with Thin and 300 nm Thick Active Layers Simultaneously

“…Alternatively, the prolonged photovoltage decay time infers that the charge recombination is suppressed. As shown in Figure 3b [53,54] As displayed in Figure 3c, the charge extraction time is 0.33 µs for Y7-BO-based binary devices, 0.55 µs for Y6-1O-based binary devices, 0.28 µs for 30 wt% Y6-1O ternary devices, and 0.24 µs for the optimized ternary OSCs. The shortest charge extraction time of 0.24 µs means the fastest charge extraction rate in the optimized ternary OSCs.…”

Fine‐Tuning Batch Factors of Polymer Acceptors Enables a Binary All‐Polymer Solar Cell with High Efficiency of 16.11%

“…The line-cut curves show that the π-π stacking diffraction and lamellar packing peaks of PA-5 blend film were stronger, and the correlation length of 010 diffraction signals has reached the higher value of ≈26.02 Å, which reveals the more ordered inter-chain self-organization or crystallization, thus leading to a better and balanced charge carrier transport property in the device. [57,58]…”

A Vinylene‐Linker‐Based Polymer Acceptor Featuring a Coplanar and Rigid Molecular Conformation Enables High‐Performance All‐Polymer Solar Cells with Over 17% Efficiency

“…[49][50][51] Investigating the effects of molecular conformations of polymer acceptors is equally important because it plays a crucial role in modulating the properties and performance of the polymer acceptors. [52,53] First, the commonly used thiophene linker could introduce some intramolecular twisting between the linker and the end group, which could have negative impact on the properties of the polymer. Second, the thiophene linker could also introduce some "asymmetry" and "randomness" to the polymer backbone, because there is ≈30-degree angle between the two single bonds linked to thiophene unit.…”