Dithienogermole As a Fused Electron Donor in Bulk Heterojunction Solar Cells

Abstract

We report the synthesis and bulk heterojunction photovoltaic performance of the first dithienogermole (DTG)-containing conjugated polymer. Stille polycondensation of a distannyl-DTG derivative with 1,3-dibromo-N-octyl-thienopyrrolodione (TPD) results in an alternating copolymer which displays light absorption extending to 735 nm, and a higher HOMO level than the analogous copolymer containing the commonly utilized dithienosilole (DTS) heterocycle. When polyDTG-TPD:PC(70)BM blends are utilized in inverted bulk heterojunction solar cells, the cells display average power conversion efficiencies of 7.3%, compared to 6.6% for the DTS-containing cells prepared in parallel under identical conditions. The performance enhancement is a result of a higher short-circuit current and fill factor in the DTG-containing cells, which comes at the cost of a slightly lower open circuit voltage than for the DTS-based cells.

On the morphology of polymer‐based photovoltaics

“…A 7.3% efficiency was obtained in an inverted device. 103,104 Diketopyrrolopyrrole-Based Polymer Recently, conjugated polymers based on diketopyrrolopyrrole (DPP) have been studied extensively for the optoelectronic applications including both organic field effect transistors (OFETs) and OPVs. Owing to the planar conjugated bicyclic structure, which leads to strong p-p interactions and high crystallinity, DPP-based conjugated polymers exhibit high hole-mobilities and high power conversion efficiencies.…”

Incremental optimization in donor polymers for bulk heterojunction organic solar cells exhibiting high performance

“…In this context, several copolymers of benzo [1,2- 17 2,7-carbazole (CBz), 6,8 13 have been reported that exhibit PCE of 6% or above in BHJ organic solar cell devices (Fig. 2).…”

“…The introduction of strong electron acceptors into the polymer backbones impart a low HOMO level and hence a lower band gap of the polymers. 1,2,4 BT is one of the widely used electron-deficient units, 6,8,9 and recently several other electron-deficient moieties such as PyT, 11 thieno [3,4-c]pyrrole-4,6-dione (TPD), 13,17,18 NT, 7 and isoindigo 5 have been reported. In addition, fluorine-substituted BT, 12 TT, 1-4,21 and TAZ 13 have also been explored (Fig.…”

“…1,2,4,21,53 Similarly, several low band-gap polymers were reported using the electron-deficient TPD unit. 13,15,17,18,54 For example, Frechet et al reported polymers (P1-3) bearing BDT and TPD units with variable alkyl side chains attached to the TPD unit. 15 Among these, P3 containing a less bulky octyl side chain on the TPD unit, exhibited enhanced p-p ordering and crystallinity in the solid state, even in the presence of PCBM.…”

Benzo[1,2-b:4,5-b′]dithiophene and benzotriazole based small molecule for solution-processed organic solar cells

“…Intensive interdisciplinary efforts have been dedicated to improving the power conversion efficiencies (PCEs) of solution-processed polymer bulk heterojunction (BHJ) solar cells [4][5][6][7][8][9][10]. More recently, BHJ OSCs using solution-processed small molecules as donors have also attracted increasing attentions [11][12][13][14][15].…”