Silicon Atom Substitution Enhances Interchain Packing in a Thiophene‐Based Polymer System

Abstract

A new silole‐containing low bandgap polymer is synthesized by replacing the 5‐position carbon of PCPDTBT with a silicon atom (PSBTBT). Through experiments and computational calculations, we show that the material properties, particular the packing of polymer chains, can be altered significantly. As a result, the polymer changes from amorphous to highly crystalline with the replacement of the silicon atom.

A low band gap co-polymer of dithienogermole and 2,1,3-benzothiadiazole by Suzuki polycondensation and its application in transistor and photovoltaic cells

“…All four films showed a strong diffraction peak at 25.4 degree (2θ) corresponding to a d-spacing of 3.51 Ǻ, which we attribute to the π-π stacking distance of PGeBTBT backbones. 55 This is similar to that observed in the Si analogue, 3 but significantly smaller than the typical distances of 3.7-3.8 Ǻ observed for thiophene polymers like P3HT. 20 The films also show a pronounced peak around 5° attributable to lamellar packing of the polymer backbones.…”

“…Heating the solution did not significantly alter the absorption wavelengths, although the peak at 700 nm increased in intensity with respect to the peak at 756 nm, possibly indicating that the longer wavelength peak is related to aggregation effects in 20 solution, similar to the silicon bridged analogues. 3,14 Upon film formation there is a small red shift in the both the shoulder (714 nm) and absorption maxima (778 nm), which are suggestive of enhanced backbone planarisation and ordering compared to the solution state. Nevertheless it is apparent that the polymer 25 exhibits appreciable aggregation in solution even upon heating, in agreement with our GPC results.…”

On the morphology of polymer‐based photovoltaics

“…16(b,c)]. 99,100 The higher crystallinity of the polymer is thought to be responsible for the better charge transport and reduced bimolecular recombination. Thermal annealing was demonstrated to be effective to increase PCE from 3.8 to 5.6%.…”

Combinatorial Screening of Polymer:Fullerene Blends for Organic Solar Cells by Inkjet Printing

“…[ 12 ] Although the chemical structure of PCPDTBT and PSBTBT is almost identical, apart from the bridging C-atom in the backbone that is replaced by a Si-atom, PSBTBT shows a higher crystallinity than PCP-DTBT. [ 13,14 ] Power effi ciencies in the range of 3.5% to 3.8% have been reported for PSBTBT and PCPDTBT solar cells. [ 13 , 15 ] Further increase of the power effi ciency was obtained either by using an additive in the blend composition, resulting in effi ciencies up to 5.5% for the polymer PCPDTBT, [ 16 ] or by a post-processing annealing step, whereby an effi ciency of 5.6% was reported for PSBTBT.…”