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Increased Exciton Delocalization of Polymer upon Blending with Fullerene
Author(s) -
Gautam Bhoj,
Klump Erik,
Yi Xueping,
Constantinou Iordania,
Shewmon Nathan,
Salehi Amin,
Lo Chi Kin,
Zheng Zilong,
Brédas JeanLuc,
Gundogdu Kenan,
Reynolds John R.,
So Franky
Publication year - 2018
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201801392
Subject(s) - polarizability , materials science , exciton , delocalized electron , excited state , fullerene , chemical physics , polymer , organic solar cell , dissociation (chemistry) , spectroscopy , photochemistry , molecular physics , chemistry , atomic physics , condensed matter physics , organic chemistry , molecule , physics , quantum mechanics , composite material
Interfaces between donor and acceptor in a polymer solar cell play a crucial role in exciton dissociation and charge photogeneration. While the importance of charge transfer (CT) excitons for free carrier generation is intensively studied, the effect of blending on the nature of the polymer excitons in relation to the blend nanomorphology remains largely unexplored. In this work, electroabsorption (EA) spectroscopy is used to study the excited‐state polarizability of polymer excitons in several polymer:fullerene blend systems, and it is found that excited‐state polarizability of polymer excitons in the blends is a strong function of blend nanomorphology. The increase in excited‐state polarizability with decreased domain size indicates that intermixing of states at the interface between the donor polymers and fullerene increases the exciton delocalization, resulting in an increase in exciton dissociation efficiency. This conclusion is further supported by transient absorption spectroscopy and time‐resolved photoluminescence measurements, along with the results from time‐dependent density functional theory calculations. These findings indicate that polymer excited‐state polarizability is a key parameter for efficient free carrier generation and should be considered in the design and development of high‐performance polymer solar cells.