Random Copolymers Allow Control of Crystallization and Microphase Separation in Fully Conjugated Block Copolymers

Abstract

Thin films of fully conjugated donor−acceptor block copolymers composed of an electron donating block and an electron accepting block can be used as single component photoactive layers in organic photovoltaic (OPV) devices. In order to realize their full potential, control over microphase separation and thin-film morphology are critical. In conjugated block copolymer systems where one or more blocks can crystallize, the morphological evolution is governed by the competition between microphase separation and crystallization. In this work, we control crystallization of fully conjugated block copolymers with a random copolymer block. We suppress the crystal packing of poly(3-hexylthiophene-2,5-diyl) (P3HT) through the insertion of a small number of 3-octylthiophene (3OT) units within the chains, yielding poly(3hexylthiophene-2,5-diyl-random-3-octylthiophene-2,5-diyl) (P[3HT-r-3OT]). While crystallization of P3HT dominates the morphology and prevents microphase separation in poly(3-hexylthiophene-2,5-diyl)-block-poly((9,9-dioctylfluorene-2,7-diyl)alt-(4,7-di(thiophene-2-yl)-2,1,3-benzothiadiazole)-5′,5″-diyl) (P3HT-b-PFTBT), modest levels of 3OT suppress crystallization in P[3HT-r-3OT]-b-PFTBT, and permit microphase separation. Thus, we demonstrate that incorporating a random copolymer into a donor−acceptor block copolymer can increase control over microphase separation and lead to enhanced performance in OPV devices.

Control of aggregated structure of photovoltaic polymers for high‐efficiency solar cells

“…For instance, the PFTBT blocks incorporated into copolymer poly(3-hexylthiophene-2,5-diyl)-block-poly((9,9-dioctylfluo rene-2,7-diyl)-alt-(4,7-di(thiophene-2-yl)-2,1,3-benzothiadia zole)-5′,5″-diyl) (P3HT-b-PFTBT) could suppress the strong crystallization of P3HT blocks caused by the molecular ordering during casting. [154,289] The suppressed crystallization of P3HT formed a favorable microphase structure during TA in 195°C. Through the copolymerization strategy and annealing, the P3HT-b-PFTBT-based single component PSCs obtained a promising PCE of 3.2%.…”

Insights into Excitonic Dynamics of Terpolymer-Based High-Efficiency Nonfullerene Polymer Solar Cells: Enhancing the Yield of Charge Separation States

“…This strategy can easily adjust the energy level and absorption spectrum of terpolymer by controlling the D/A unit ratio in the polymer backbone . Also, the crystallization and microphase separation of the copolymer could be modulated by random copolymer methods . Furthermore, the fine-tuning solid-state packing of the photoactive layer could remarkably improve the photovoltaic characteristics through side-chain engineering using random polymerization .…”

AIE-Active Random Conjugated Copolymers Synthesized by ADMET Polymerization as a Fluorescent Probe Specific for Palladium Detection

“…Such control over polymer architecture is highly beneficial for tuning the material properties, such as the solubility, optical absorption bands, and the packing morphology in the aggregated states, which facilitate diverse potential applications of CPs. 29 Palladium (Pd) finds extensive catalytic usage in the chemical and petroleum industry. Increased Pd pollutions in the environment and biological systems have been recognized recently.…”

“…The monomer distribution in the CP by this approach is different from that of alternating polymers obtained by polycondensation reactions. Such control over polymer architecture is highly beneficial for tuning the material properties, such as the solubility, optical absorption bands, and the packing morphology in the aggregated states, which facilitate diverse potential applications of CPs. , …”