Carbazole–Phenylbenzotriazole Copolymers as Absorber Material in Organic Solar Cells

Abstract

An alternating copolymer comprising a 2,7functionalized carbazole donor and a 2-phenyl-2H-benzotriazole acceptor with an octyldodecyloxy substituent was synthesized. The polymer was blended with [6,6]-phenyl C 71-butyric acid methyl ester (PC 71 BM) and incorporated as absorber layer into solution processed organic solar cells. By adding the processing additive 1,8-diiodooctane (DIO) to the host solvent 1,2dichlorobenzene (DCB), the solar cell fill factor increased to remarkable 70% and the power conversion efficiency approached 4.6%. Low-energy scanning transmission electron microscopy (low-keV STEM) investigations indicated a finer bulk morphology of the active layer upon deposition from DCB:DIO. Further, the low-energy shoulder of the absorption spectrum was enhanced, indicating stronger polymer aggregation. According to external quantum efficiency measurements, the enhanced absorption also promoted better photon harvesting. Grazing incidence X-ray diffraction experiments revealed face-on polymer aggregates being beneficial for the vertical hole transport.

Design and control of organic semiconductors and their nanostructures for polymer–fullerene-based photovoltaic devices

“…122 However, the bandgap of PCDTBT (1.89 eV) is larger than the value (1.5-1.7 eV) of the ideal polymers for the PCE exceeding 10%. Recently, to narrow the bandgap of PCDTBT without sacricing the low HOMO level, further different electron-accepting monomers, including phenylbenzotriazole 123 and quinoxaline-based units, 124 have been incorporated into 2,7-carbazole based copolymers. However, the PCE values of the PSCs with these polymers are still comparable to or even lower than those of the PCDTBT-based devices.…”

Effect of solvent additive and ethanol treatment on the performance of PIDTDTQx:PC71BM polymer solar cells

“…Liang et al reported that the PCE of PSCs with PTB7: [6,6]-phenyl-C71-butyric acid methyl ester (PC 71 BM) as active layer was increased to 7.40% from 3.92% upon mixing of 3 vol% DIO to the host solvent chlorobenzene (CB) [23]. Klein et al also reported that the PCE of PSCs with PCDTPBt:PC 71 BM as active layer was increased from 2.5% to 4.6% by adding 3 vol% solvent additive DIO to the host solvent 1,2-dichlorobenzene (DCB) [24]. Recently, Gedefaw et al reported that the PCE of PSCs with PBDTFQ-T:PC 61 BM as active layer was increased from 2.18% to 5.30% by adding 3 vol% solvent additive DIO, the PCE improvement should be attributed to the finer adjustment on nanostructure of active layer for the better balance between charge transport properties and light absorption [25].…”

Modeling approach to derive the anisotropic complex refractive index of polymer:fullerene blends for organic solar cells utilizing spectroscopic ellipsometry

“…[13][14][15][16][17][18][19][20][21][22][23][24] Therefore, an urgent need for flexible optical descriptions of bulk-heterojunctions emerged, which use parametric descriptions and allow for individual adjustments.…”