General Information

Full name	Poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3’’’-di(2-octyldodecyl)-2,2’;5’,2’’;5’’,2’’’-quaterthiophen-5,5’’’-diyl)]
Synonyms	PffBT4T-2OD
Chemical formula	(C62H88F2N2S5)n
CAS number	1644164-62-4
HOMO / LUMO	HOMO = -5.34 eV, LUMO = -3.69 eV [1]
Solubility/processing solvents	Dichlorobenzene or Chlorobenzene+dichlorobenzene (1:1 v/v) at elevated temperature ca. 110 °C
Classification / Family	Benzothiadiazole, Fluorinated benzothiadiazole, Heterocyclic five-membered ring, Organic semiconducting materials, Low band gap polymers, Organic Photovoltaics, Polymer Solar Cells

 

 Batch details

Batch number	MW	MN	PDI
M301	117,490	54,900	2.14
M302	172,033	83,008	2.07
M303	112,707	55,674	2.02

 

 

 

Applications

PffBT4T-2OD (PCE11) is a low band-gap (1.65 eV) semiconducting polymer for organic photovoltaics (OPVs), which has reached power conversion efficiencies (PCEs) approaching 11% [1]. These efficiencies are a result of the high crystallinity of the polymer, providing excellent hole transport mobilities on the order of 10-2 cm2V-1s-1, and the ability to use a thick active layer, resulting in improved light absorption.

The size and position of the alkyl chains of PffBT4T-2OD are critical to its temperature dependant aggregation properties, enabling control over the aggregation and crystallisation of the polymer to produce an efficient donor:acceptor film morphology.

Polymer PCE11 was targeted by reacting 4,7-bis(5-bromo-4-(2-octyldodecyl)thiophen-2-yl)-5,6-difluorobenzo[c][1,2,5]-thiadiazole with 2,5-bis(trimethylstannyl)thieno[3,2-b]thiophene engaging Stille Coupling reaction.

PCE11 (PffBT4T-2OD) synthesis with 4,7-bis(5-bromo-4-(2-octyldodecyl)thiophen-2-yl)-5,6-difluorobenzo[c][1,2,5]-thiadiazole with 2,5-bis(trimethylstannyl)thieno[3,2-b]thiophene as starting materials engaging Stille Coupling reaction.

 

Usage Details

The structure of the high-performance (10 - 11%) devices was:

ITO / ZnO / PffBT4T-2OD:PC70BM (200 – 300 nm) / MoO3 or V2O5 (20 nm) / Al (100 nm)

PffBT4T-2OD:PC70BM solution details:

• Blend ratio: 1:1.2,
• Polymer concentration: 9 mg/ml,
• Solvent: 1:1 blend of chlorobenzene and dichlorobenzene,
• Additive: 3% diiodooctane,
• Heating: 85°C for dissolution,

It is important to note that this solution (and the substrate being deposited onto) must be heated for spin casting, with the ideal temperature being 60 – 80°C. It is reported that a solution and substrate pre-heating temperature of 110°C should be used to allow for cooling that will occur before deposition.

 

Literature and Reviews

1. Aggregation and morphology control enables multiple cases of high-efficiency polymer solar cells, Y. Liu, et al., Nat. Comm., 5, 5293 (2014)
2. High-efficiency non-fullerene organic solar cells enabled by a difluorobenzothiadiazole-based donor polymer combined with a properly matched small molecule acceptor, J. Zhao et al., Energy Environ. Sci., 8, 520-525 (2015)