Extended Data Fig. 7: Application of catalysed n-doping of organic polymers to n-type organic thermoelectronic devices.

a, Illustration of an n-type thermoelectric device where this method can be used to generate an n-doped organic semiconductor film. b, N-type thermoelectric performance of an off-centre spin-casted, sequentially doped f-BTI2TEG-FT+PBTI blend films, using AuNP catalyst. Recently, side-chain engineering of conjugated polymers with hydrophilic groups⁵⁹ has shown improved n-dopability and conductivity with N-DMBI-H due to enhanced dopant/semiconductor miscibility. For example, by simply replacing the hydrophobic alkyl chain (2-octyldodecyl) in f-BTI2-FT⁵¹ with triethylene glycol (TEG)-based chain in f-BTI2TEG-FT (Supplementary scheme 1, Supplementary Figs. 34–41), σ of uncatalysed N-DMBI-H doping was found to increase from (8.9 ± 0.5)  × 10⁻³ S cm⁻¹ to 1.4 ± 0.1 S cm⁻¹, respectively. However, N-DMBI-H+AuNP doping of f-BTI2TEG-FT can achieve a σ of 25.1 ± 0.6 S cm⁻¹ (blend doping), 38.4 ± 2.2 S cm⁻¹ (sequential doping, on-centre), and 74.3 ± 4.6 S cm⁻¹ (sequential doping, off-centre) (Table 1, Supplementary Figs. 42, 43), despite a low transistor mobility of 0.018 cm² V⁻¹ s⁻¹ (Supplementary Fig. 44, Supplementary Table 6). Impressively, an even higher σ of 104.0 ± 7.9 S cm⁻¹ (maximum 116.3 S cm⁻¹) can be obtained by adding a small amount (15wt%) of the high mobility PBTI polymer⁵⁰ (M_n = 35.5 kDa) to f-BTI2TEG-FT, which serves as high-mobility pathways between doped f-BTI2TEG-FT domains for improved charge transport⁴². Thus, based on the latter blend, we fabricated an organic thermoelectric device which showed a remarkable power factor (PF) of 65.7 ± 5.5 μW m⁻¹ K⁻² with a Seebeck coefficient of −79.5 ± 2.8 μV K⁻¹ (Extended Data Fig. 7b, Supplementary Fig. 45). The conductivity and power factor values are among the highest to date for solution-processed molecular n-doped conjugated polymers^12,46. Error bars represent the standard deviations from their mean values.