Impact of the Crystalline Packing Structures on Charge Transport and Recombination via Alkyl Chain Tunability of DPP-Based Small Molecules in Bulk Heterojunction Solar Cells

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• 作者：Chang Eun Song ; Yu Jin Kim ; Sanjaykumar R. Suranagi ; Gururaj P. Kini ; Sangheon Park ; Sang Kyu Lee ; Won Suk Shin ; Sang-Jin Moon ; In-Nam Kang ; Chan Eon Park ; Jong-Cheol Lee
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：May 25, 2016
• 年：2016
• 卷：8
• 期：20
• 页码：12940-12950
• 全文大小：682K
• 年卷期：0
• ISSN：1944-8252

文摘

A series of small compound materials based on benzodithiophene (BDT) and diketopyrrolopyrrole (DPP) with three different alkyl side chains were synthesized and used for organic photovoltaics. These small compounds had different alkyl branches (i.e., 2-ethylhexyl (EH), 2-butyloctyl (BO), and 2-hexyldecyl (HD)) attached to DPP units. Thin films made of these compounds were characterized and their solar cell parameters were measured in order to systematically analyze influences of the different side chains of compounds on the film microstructure, molecular packing, and hence, charge-transport and recombination properties. The relatively shorter side chains in the small molecules enabled more ordered packing structures with higher crystallinities, which resulted in higher carrier mobilities and less recombination factors; the small molecule with the EH branches exhibited the best semiconducting properties with a power conversion efficiency of up to 5.54% in solar cell devices. Our study suggested that tuning the alkyl chain length of semiconducting molecules is a powerful strategy for achieving high performance of organic photovoltaics.