Fig. 4: Electrical conductivity patterning in PBTTT films by local doping.

a Chemical structures of PBTTT and BCF. b Conductivity σ of PBTTT films doped through gate by annealing for 1 min at temperature T. Solution-deposited dopant layers comprised BCF (black dot) and BCF + 5 wt% biphenyl (‘BP’; blue triangle) added as a co-solvent. Dashed line indicates the melting temperature of BP. c Transmitted-light micrographs for the films in b. d Selected Raman spectra of doped PBTTT films, with conductivities indicated. Spectra are normalised by the intensity of the peak at ~1393 cm⁻¹; shaded region highlights the peaks used for estimating conductivity. e Raman intensity ratio r_R of the maximum intensities of the ~1393 cm⁻¹ and ~1417 cm⁻¹ peaks of PBTTT as a function of σ. Dotted line indicates a curve fit to the data. f Maximum conductivities obtained in line patterns of doping induced by scanning laser excitation at 532 nm for the indicated incident power P and writing speed v. Conductivities were extracted by Raman mapping of r_R using the calibration data in e. g Transmitted-light micrograph of laser-patterned (P = 7 mW, v = 3 μm s⁻¹) RFID-antenna-type structure. h Raman map of r_R for the indicated area and (i) the corresponding average profiles of r_R (left ordinate) and σ (right ordinate).