Batch‐to‐Batch Variation of Polymeric Photovoltaic Materials: its Origin and Impacts on Charge Carrier Transport and Device Performances. Issue 16 (14th July 2014)

• Record Type: Journal Article
• Authors: Lee, Harrison Ka Hin; Li, Zhao; Constantinou, Iordania; So, Franky; Tsang, Sai Wing; So, Shu Kong
• Is Part Of: Advanced energy materials. Volume 4:Issue 16(2014)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2014-07-14
• Subjects: Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.201400768
• Languages: English
• ISSNs: 1614-6832

Abstract

<abstract abstract-type="main" xml:lang="en"> <title> <x xml:space="preserve">Abstract</x> </title> <p>A detailed investigation of the impact of molecular weight distribution of a photoactive polymer, poly[<italic>N</italic>‐9′‐heptadecanyl‐2, 7‐carbazole‐<italic>alt</italic>‐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<sup>−5</sup> to 1.6 × 10<sup>−8</sup> cm<sup>2</sup> V<sup>−1</sup> s<sup>−1</sup>. 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.</p> </abstract>