All chemicals, P3HT (poly(3-hexylthiophene), regioregular; mol. wt. 50000 -100000), F 4 TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) and chlorobenzene, were purchased from Sigma Aldrich and used without further purification. Sample for steady state absorption in the visible and IR, as well as 2DES measurements were prepared by the method reported in the literature. We prepared 1 mg ml -1 orange-red coloured solution of F 4 TCNQ using chlorobenzene. The solution was heated to 130 • C for 30 mins and then kept at 110 2D electronic spectroscopy measurements and experimental conditions Details of the experimental set-up for 2D electronic measurements has been described previously by our group. Briefly, ∼16 fs compressed pulses are generated from a home-built non-linear optical parametric amplifier (NOPA), using a combination of a prism pair and deformable mirror (OKO Technologies). A commercial femtosecond PHAROS laser, by Light Conversion Inc., is used to pump the NOPA. An all-reflective 2D spectrometer based on a diffractive optic (Holoeye) with a phase stability of lamda/160 was used for the measurements. Frequency-resolved optical grating (FROG) measurements were used to characterize the temporal resolution of the compressed beam. A commercial software application FROG3 was used to analyse the FROG traces. The 2D set-up also includes a Sciencetech spectrometer model 9055, which is coupled to CCD linear array camera (Entwicklungsburo Stresing).