Premium
Batch‐to‐Batch Variation of Polymeric Photovoltaic Materials: its Origin and Impacts on Charge Carrier Transport and Device Performances
Author(s) -
Lee Harrison Ka Hin,
Li Zhao,
Constantinou Iordania,
So Franky,
Tsang Sai Wing,
So Shu Kong
Publication year - 2014
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201400768
Subject(s) - materials science , polymer , charge carrier , gel permeation chromatography , photovoltaic system , molar mass distribution , chemical physics , electron mobility , permeation , polymer solar cell , chemical engineering , analytical chemistry (journal) , optoelectronics , organic chemistry , chemistry , membrane , composite material , engineering , biology , ecology , biochemistry
A detailed investigation of the impact of molecular weight distribution of a photoactive polymer, poly[ N ‐9′‐heptadecanyl‐2,7‐carbazole‐ alt ‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)] (PCDTBT), on photovoltaic device performance and carrier transport properties is reported. It is found that different batches of as‐received polymers have substantial differences in their molecular weight distribution. As revealed by gel permeation chromatography (GPC), two peaks can generally be observed. One of the peaks corresponds to a high molecular weight component and the other peak corresponds to a low molecular weight component. Photovoltaic devices fabricated with a higher proportion of low molecular weight component have power conversion efficiencies (PCEs) reduced from 5.7% to 2.5%. The corresponding charge carrier mobility at the short‐circuit region is also significantly reduced from 2.7 × 10 −5 to 1.6 × 10 −8 cm 2 V −1 s −1 . The carrier transport properties of the polymers at various temperatures are further analyzed by the Gaussian disorder model (GDM). All polymers have similar energetic disorders. However, they appear to have significant differences in carrier hopping distances. This result provides insight into the origin of the molecular weight effect on carrier transport in polymeric semiconducting materials.