Molecular weight and end capping effects on the optoelectronic properties of structurally related ‘heavy atom’ donor–acceptor polymers

Abstract

Molecular weight and end group differences produce distinct optoelectronic and morphological properties in heavy atom donor–acceptor polymers of the same repeat unit structure.

Marriage of heavy main group elements with π-conjugated materials for optoelectronic applications

“…4; 21-41). [57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72] The dithienogermole containing polymers are generally obtained by metal-catalyzed cross-coupling methodologies such as the Stille, Suzuki-Miyaura and Sonogashira reactions, and very high number average molecular weights (M n ) of up to 133000 g mol -1 have been occasionally reported. Due to d-block contraction, 73,74 the electronegativity of germanium is slightly closer to carbon than the related silicon species, 75 therefore reducing the polarization of the Ge-C bond and rendering aryl germanes more tolerable towards bases and nucleophiles than the related aryl silanes.…”

“…This selenium-containing polymer 199 is also photoluminescent with blue-light emission centered at 452 nm and a measured quantum yield of 0.32 %. 71 These polymers were obtained with molecular weights (M n ) as high as 33000 g mol -1 and PDI values around 2.0. These benzoselenodiazole-co-polymers were then incorporated into BHJ solar cells with PC 71 BM as the acceptor material in the light harvesting/charge creation layer, with PCE values nearing 2.0 % in unoptimized devices.…”

Dithieno[3,2-b:2′,3′-d]arsole-containing conjugated polymers in organic photovoltaic devices

“…[11][12][13] A common example of the use of heavy atoms is in the class of materials known as dithienoheteroles, in which two thiophene rings are fused by a bridging heteroatom to form a tricylic structure. Dithienoheteroles utilizing heavy bridging atoms such as silicon, germanium, and tin have been reported, [14][15][16][17][18] while those containing the group 15 elements nitrogen and phosphorus, especially dithieno[3,2-b:2',3'-d]pyrroles and dithieno[3,2-b:2',3'-d]phospholes (DTPs) have seen use in many areas of organic electronics. [19][20][21] Dithienophospholes in particular exhibit a number of interesting properties that make them potentially useful candidates for use in OPV devices, including a high degree of optoelectronic tunability via the alteration of the exocyclic groups.…”

“…This complicated the removal of low molecular weight oligomers, which are known to be detrimental to device performance. 15,44 Therefore shorter 2-ethylhexyl chains were used on co-monomer 4 instead to improve the effectiveness of the Soxhlet separation on P2. This was only partially successful since hexane extraction still removed a significant portion of the polymer (84% yield).…”

Air-Stable n-channel Diketopyrrolopyrrole−Diketopyrrolopyrrole Oligomers for High Performance Ambipolar Organic Transistors

“…Remarkable progress in the performance of optoelectronic devices have been realized by incorporating DPP unit in polymers and oligomers. 12,13,14 DPP is comprised of an electron deficient fused lactam ring, flanked by donors. With the DPP acceptor unit, the frontier molecular orbital positions and the intramolecular and intermolecular interactions can be tuned to achieve the desired optoelectronic and transport properties.…”