Two-Dimensionally Extended π-Conjugation of Donor–Acceptor Copolymers via Oligothienyl Side Chains for Efficient Polymer Solar Cells

Abstract

A series of two-dimensional conjugated polymers containing π-conjugated oligothienyl side chains, namely PBDT2FBT-T1, PBDT2FBT-T2, PBDT2FBT-T3, and PBDT2FBT-T4, was designed and synthesized to investigate the effect of two-dimensionally extended π-conjugation on the polymer solar cell (PSC) performance. The oligothienyl units introduced into the side chains significantly affect the optoelectronic properties of the parent polymers as well as the performances of the resulting solar cell devices by altering the molecular arrangement and packing, crystalline behavior, and microstructure of the polymer:PC 71 BM blend films. The crystallinity and blend morphology of the polymers can be systematically controlled by tuning the π-conjugation length of side chains; PBDT2FBT-T3 exhibited the most extended UV/vis light absorption band and the highest charge mobility, leading to a high short-circuit current density up to 12.5 mA cm −2 in the relevant PSCs. The PBDT2FBT-T3:PC 71 BM-based PSC exhibited the best power conversion efficiency of 6.48% among this series of polymers prepared without the use of processing additives or post-treatments. These results provide a new possibility and valuable insight into the development of efficient medium-bandgap polymers for use in organic solar cells.

Design and application of volatilizable solid additives in non-fullerene organic solar cells

“…As is known, the optical properties of organic semiconductors have a strong connection with the aggregation behavior in solid films 35 , 36 . First, as depicted in Fig.…”

Recent Advances in Morphology Optimization for Organic Photovoltaics

“…PBDT2FBT contains thienyl groups and has the finest film morphology due to its higher solubility and the similarity of its surface energy to that of PC 70 BM. The authors also enabled 2D π‐conjugation by using oligothienyl side chains . Various PBDT2FBT polymers were synthesized with alkylated thienyl, bithienyl, terthienyl, and quaterthienyl side chains.…”

Influence of the positions of thiophenes and side chains on diketopyrrolopyrrole based narrow band-gap small molecules for organic solar cells

“…where V oc is the open circuit voltage, e is the elementary charge and 0.3 V is an empirical factor, the V oc of the OSCs devices based on the four compounds are approximately 0.70 V, which may limit the improvement of the PCE [38]. As shown in Table 2, the OSC based on DPPTTC6, DPPTTC8, IDPPTIC8 and IDPPTIEH without annealing delivers a PCE of 0.44%, 0.91%, 0.93% and 1.11%, respectively.…”