Tradeoff between Intermolecular Interaction and Backbone Disorder by High Molecular Dipole Block for Improving Blend Morphology of Polymer Solar Cells

Abstract

Constructing terpolymer has attracted increasing attention as a strategy to improve the performance of polymer solar cell. Terpolymer usually offers an opportunity to lower the frontier molecular orbital energy level, introduces additional absorption band and sometimes optimizes the morphology of the active blend. Generally, the additional segment in terpolymer backbone inevitably introduces backbone disorder, which causes entropy rises. However, selecting a suitable dipole unit introduces extra driving forces for crystallization by enhancing intermolecular interactions. This provides a handy knob for tradeoff between intermolecular interaction and backbone disorder, thus regulating the blend morphology. Herein, a high dipole and electron‐deficient group of pyrrolo[3,4‐f]benzotriazole‐5,7(6H)‐dione (TzBI) is incorporated into the high‐performance donor polymer and a series of terpolymers with different content of TzBI are designed. As expected, the morphology is optimized gradually for improving charge generation and charge transport, also suppressing charge recombination. The champion device with 10% TzBI exhibited a power conversion efficiency (PCE) of 18.36%, which is 5% increase compared to the controlled device. This study presents a charming terpolymer strategy by highly electron‐deficient and high dipole segment to realize a tradeoff between intermolecular interaction and backbone disorder, facilitating the optimization of morphology and elevation of fill factor and device efficiency.

Y‐Type Non‐Fullerene Acceptors with Outer Branched Side Chains and Inner Cyclohexane Side Chains for 19.36% Efficiency Polymer Solar Cells

“…This is likely due to the D18 crystallized earlier which guided the crystallization process of the NF‐SMAs. [ 55 ] The face‐on configuration is considered favorable for out of plane charge transport. Scatterings from D18 and the NF‐SMAs were separated by fitting and a comparable CCL value around 10 nm for D18 were found across the neat and blend thin films, supporting that D18 was crystallized first and not affected by the NF‐SMAs.…”

Terpolymers Containing Difluorobenzoxadiazole Enable Suppressed Energy Losses and Optimal Batch‐to‐Batch Reproducibility for High‐Efficiency Organics Solar Cells

“…It is worth noting that the PCEs of all PBFBX20‐based OSCs located in a narrow range from 16.8% to 17.5%, as shown in Figure 5c and Table S12, Supporting Information, which were accompanied by almost identical V oc (0.84–0.85 V), J sc (26.9–27.3 mA cm 2 ), and FF (0.73–0.76). As a comparison, we plotted the normalized PCEs as the function of M n with several PBDB‐TF‐based terpolymers (PBDB‐TF, [7c] PM1, [7c] SZ3, [7b] T10, [ 19 ] PMZ‐10, [ 20 ] and PMD‐15 [18b] ), which were explored the relationship between PCE and M n . The corresponding parameters are listed in Table S13, Supporting Information.…”

“…As for PBFBX80 blends, the π – π distance sharply decreases to 3.55 Å and the CCL value increases to 41.59 Å, together with multiple shape diffraction peaks appear as shown in GIWAXS image, which should be the reason for small crystalline grains Y6‐BO formed in the blend, resulting in inhomogeneous morphology. [ 18 ] The neat films exhibit gradually weaker packing and crystalline as the addition of ffBX with the ratio from 20% to 60%, while the corresponding blend films show little influence on the packing and crystalline properties of blend films. The favorable molecular packing and crystalline can remain when ffBX is added in proper proportion, which leads to similar and high FF (from 0.72 to 0.76).…”

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

“…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. Obviously, electrostatic dipole out-of-plane of the polymer plane is more effective in providing intermolecular interactions between flat polymers.…”