High‐Resolution Spectroscopic Mapping of the Chemical Contrast from Nanometer Domains in P3HT:PCBM Organic Blend Films for Solar‐Cell Applications

Abstract

A high‐resolution near‐field spectroscopic mapping technique is successfully applied to investigate the influence of thermal annealing on the morphology of a poly(3‐hexylthiophene) and [6,6]‐penyl‐C61 butyric acid methyl ester (P3HT:PCBM) blend film. Based on the simultaneously recorded morphological and spectroscopic information, the interplay among the blend film morphology, the local P3HT:PCBM molecular distribution, and the P3HT photoluminescence (PL) quenching efficiency are systematically discussed. The PL and Raman signals of the electron donor (P3HT) and acceptor (PCBM) are probed at an optical resolution of approximately 10 nm, which allows the chemical nature of the different domains to be identified directly. In addition, the local PL quenching efficiency, which is related to the electron transfer from P3HT to PCBM, is quantitatively revealed. From these experimental results, it is proposed that high‐resolution near‐field spectroscopic imaging is capable of mapping the local chemical composition and photophysics of the P3HT:PCBM blends on a scale of a few nanometers.

Operational electrochemical stability of thiophene-thiazole copolymers probed by resonant Raman spectroscopy

“…A reduced FWHM indicates that the distribution of C= =C modes in different conformational environments is narrower indicating an increase in energetic order. 22,35,36 The narrowing observed here when thiazole units are present is consistent with the increased backbone planarity mentioned above. This reduction in FWHM primarily results from a reduction in intensity in the higher energy part of this Raman peak, which is particularly associated with the disordered polymer phase, so this result indicates an overall increase in the degree of molecular order with increasing thiazole content.…”

“…[34][35][36][37][38][39] In each case, the ground-state geometries of the molecules were first optimized in the gas phase (the hexyl side chains were replaced by methyl side groups to reduce computation time) and the Raman spectra of these optimized structures were then calculated ( Figure SI.1 40 ). …”

Tip-enhanced Raman spectroscopy: principles and applications

“…Since then TERS has rapidly progressed to become a non-destructive scanning probe microscopy tool for surface chemical characterisation [6], and opened up the opportunities to study single macro-molecules with sub-nm spatial resolution [7]. Over the last 15 years, the technique has been used to study scientific problems in biology [8], photovoltaics [9], catalysis [10], semiconductors [11], carbon nanotubes [12], graphene [13] and single molecule detection [7].…”

In-situ monitoring of molecular vibrations of two organic semiconductors in photovoltaic blends and their impact on thin film morphology

“…6,7 Raman spectroscopy is an inelastic light scatteringbased technique which probes the vibrational modes of a material and it is a very valuable tool to probe the morphology of conjugated polymer:fullerene thin films. [8][9][10][11][12] It has a number of advantages including probing molecular order, 8,12,13 molecular orientation, 14,15 in-situ chemical reactions, [16][17][18] and chemical mapping. 9,12,19 Although Raman spectroscopy is a valuable tool to study the morphology of conjugated polymer:fullerene films, usually Raman spectrum of only one component (polymer) is probed.…”

“…[8][9][10][11][12] It has a number of advantages including probing molecular order, 8,12,13 molecular orientation, 14,15 in-situ chemical reactions, [16][17][18] and chemical mapping. 9,12,19 Although Raman spectroscopy is a valuable tool to study the morphology of conjugated polymer:fullerene films, usually Raman spectrum of only one component (polymer) is probed. This is because fullerene molecules, such as (6,6)-phenyl-C 61 -butyric acid methyl ester (PCBM), absorb at ultra-violet region, which produces small Raman scattering signal under visible laser excitation commonly used for the conventional Raman spectroscopy.…”