Synergistically Improving the Absorption, Energy Level, and Crystallization of PM6 by a Dicyanobenzothiadiazole Block-Based Terpolymer Strategy

Abstract

The current top performing polymer solar cells (PSCs) are predominately based on the polymer donor material PM6 paired with Y-series small-molecule acceptors. For the limited improvement space for the Y-series acceptors, it is of great importance to explore strategies to optimize the molecular structure of PM6 for further elevation of the power conversion efficiencies (PCEs). Evidently, the terpolymer strategy is an effective method to improve the inherent properties of PM6 by introducing units with different electron states as building blocks in the copolymer backbone. In this work, a dicyanobenzothiadiazole (CNBT) group was selected and incorporated into the backbone of PM6 to form random terpolymers in a (D−A 1 ) n −(D−A 2 ) m structure with various CNBT contents. The electron-deficient CNBT group induced a strong intermolecular charge transfer, resulting in the rise of a red absorption band, which covered the absorption gap between PM6 and L8-BO around 700 nm. The high electron deficiency of CNBT groups also enabled a downshift in the highest occupied molecular orbital (HOMO) of PM6 for causing improvement of V oc . Furthermore, the high dipole moment of CNBT groups enhanced intermolecular aggregation, which helped to overcome the crystallization reduction effect of the terpolymer structures, leading to optimization of the thin-film morphology. The synergistically enhanced absorption, energy level matching, and crystallization tendency led to simultaneously increased V oc , J sc , and FF, which all contributed to a significantly increased PCE of up to 18.01% compared with the PM6-based devices.

Conjugated polymers and small molecules containing the thiophene–vinylene–thiophene (TVT) unit for organic photovoltaic applications

“…As we all know, great progress has been made in OPV performance due to the development of terpolymers. 43,77,78 Because of the unique structure, TVT has been successfully introduced into various terpolymers to adjust the polymer conguration and obtained high device performance as shown in Fig. 7.…”

18.62%‐Efficiency Binary Organic Solar Cells with a PEDOT1:PSS2.80 Buffer Layer

“…Binary nonfullerene organic solar cells (OSCs) have received tremendous attention, because of these advantages including DOI: 10.1002/adom.202302947 ease of solution manufacturing, a controllable phase-segregated morphology of the binary active layers, etc. [1][2][3][4][5][6][7][8][9][10][11][12] The binary OSCs are commonly composed of an active layer of organic donor and nonfullerene acceptors sandwiched between a poly (3,4ethylenedioxythiophene):poly(styrenesulfo nate) (PEDOT:PSS)-modified indium tin oxide (ITO) positive electrode and a lowwork function metal negative electrode. The ultimate objective of the OSCs is to develop efficient, solution-processed, and costeffective products.…”

Saddle‐Shaped Third Component with Out‐of‐Plane Electrostatic Dipole for Realizing High‐Performance Photovoltaic Donor Terpolymers

“…[19][20][21][22][23][24] However, the intermolecular binding force imparted through secondary bonding using ester, [25][26][27] cyano, [28] chlorinated, [29] and fluorinated [30] third components in PM6-based terpolymer is successful in offsetting the backbone disorder during crystallization. Another method to increase the crystallization tendency involves selecting a third component that facilitates a strong electrostatic dipole and has a high dipole moment group, such as FTAZ, [31] mono-CNTAZ, [32] CNBT, [33] TPD, [34] and TzBI. [35] The high dipole moment created in these groups is in the fused plane and can simply be achieved by adding electron-withdrawing or electron-donating groups on one side.…”