Terpolymerization and Regioisomerization Strategy to Construct Efficient Terpolymer Donors Enabling High‐Performance Organic Solar Cells

Abstract

Terpolymerization and regioisomerization strategies are combined to develop novel polymer donors to overcome the difficulty of improving organic solar cells (OSCs) performance. Two novel isomeric units, bis(2-hexyldecyl)-2,5bis(4-chlorothiophen-2-yl)thieno[3,2-b]thiophene-3,6-dicarboxylate (TTO) and bis(2-hexyldecyl) 2,5-bis(3-chlorothiophen-2-yl)thieno[3,2-b]thiophene-3,6dicarboxylate (TTI), are obtained and incorporated into the PM6 backbone via random copolymerization to form a series of terpolymers. Interestingly, it is found that different chlorine (Cl) substituent positions can significantly change the molecular planarity and electrostatic potential (ESP) owing to the steric hindrance effect of the heavy Cl atom, which leads to different molecular aggregation behaviors and miscibility between the donor and acceptor. The TTO unit features a higher number of multiple S•••O non-covalent interactions, more positive ESP, and fewer isomer structures than TTI. As a result, the terpolymer PM6-TTO-10 exhibits a much better molecular coplanarity, stronger crystallinity, more obvious aggregation behavior, and proper phase separation in the blend film, which are conducive to more efficient exciton dissociation and charge transfer. Consequently, the PM6-TTO-10:BTP-eC9-based OSCs achieve a champion power conversion efficiency of 18.37% with an outstanding fill factor of 79.97%, which are among the highest values reported for terpolymer-based OSCs. This work demonstrates that terpolymerization combined with Cl regioisomerization is an efficient approach for achieving high-performance polymer donors.

Morphology Control Realizes Fast Charge Dissociation and Transport in High-Performance All-Polymer Solar Cells

“…Furthermore, the energy levels of D18-Cl and PY-IT are shown in Figure c (The HOMO and LUMO energy levels of the active layer materials in the energy diagram were obtained from the literature), , where the open-circuit voltage ( V OC ) is mainly determined by the highest occupied molecular orbital (HOMO) energy level of the donor and the lowest unoccupied molecular orbital (LUMO) energy level of the acceptor. , In this study, the conventional device structure (ITO/PEDOT:PSS/active layer/PDINN/Ag) was used for characterizing the photovoltaic performance, as shown in Figure d. Figure a illustrates the J – V curves of the optimized devices under different additives, while Table summarizes the corresponding photovoltaic parameters.…”

Monophenyl-featured side-chain-random terpolymers for organic solar cells with an efficiency beyond 19%

“…However, due to the heterogeneous structure nature of the extra third component, the two types of terpolymers usually suffer from a severe trade-off between the intermolecular interactions and main chain disorder. 34 Therefore, a third component featuring a strong secondary bonding force or electrostatic dipole is highly desired because enhancements in the intermolecular interactions and crystallization tendency could be expected, and the resulting modification of the blend morphology could yield several high-performing terpolymers, such as PM6-BNBP 35 and DL1, 36 as have been previously reported. On the other hand, keeping the sequence of the polymer backbone unchanged and slightly tuning the side chain could be another potential pathway, in which the obtained polymers could be defined as skeleton-fixed side-chain-random terpolymers (SSTs), as studied herein.…”

Novel Narrow Band-Gap Copolymers Based on Pyridinthiadiazole for Semitransparent Organic Solar Cells

“…Unfortunately, the ST-OSCs still exhibited inferior performance relative to the traditional opaque OSCs because of the narrow absorption region and high energy loss. − Usually, the light utilization efficiency (LUE) is a comprehensive parameter to evaluate ST-OSCs. ,, Thus, numerous works recently have been involved in exploring efficient optical coatings and antireflection layers of the device to improve both LUE and AVT. − Furthermore, many researchers focus on the medium wide band-gap (WBG) donor pairing to the NFAs to obtain the high PCE of ST-OSCs with low AVT. − However, the WBG-based ST-OSCs displayed low AVT because of the absorption region covering the light response of human eyes. Thus, combining the WBG donor with NFAs is not suitable for ST-OSCs.…”