Complementary Absorbing Star-Shaped Small Molecules for the Preparation of Ternary Cascade Energy Structures in Organic Photovoltaic Cells

• Published in: Advanced functional materials Vol. 23; no. 12; pp. 1556 - 1565
• Main Authors: Cha, Hyojung, Chung, Dae Sung, Bae, Suk Young, Lee, Min-Jung, An, Tae Kyu, Hwang, Jihun, Kim, Kyung Hwan, Kim, Yun-Hi, Choi, Dong Hoon, Park, Chan Eon
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 25.03.2013; WILEY‐VCH Verlag
• Subjects: Alignment; Charge Transport; Photovoltaic Devices; Ternary Cascade Energy Structure
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201201913

Two anthracene‐based star‐shaped conjugated small molecules, 5′,5″‐(9,10‐bis((4‐hexylphenyl)ethynyl)anthracene‐2,6‐diyl)bis(5‐hexyl‐2,2′‐bithiophene), HBantHBT, and 5′,5″‐(9,10‐bis(phenylethynyl)anthracene‐2,6‐diyl)bis(5‐hexyl‐2,2′‐bithiophene), BantHBT, are used as electron‐cascade donor materials by incorporating them into organic photovoltaic cells prepared using a poly((5,5‐E‐alpha‐((2‐thienyl)methylene)‐2‐thiopheneacetonitrile)‐alt‐2,6‐[(1,5‐didecyloxy)naphthalene])) (PBTADN):[6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) blend. The small molecules penetrate the PBTADN:PC71BM blend layer to yield complementary absorption spectra through appropriate energy level alignment and optimal domain sizes for charge carrier transfer. A high short‐circuit current (JSC) and fill factor (FF) are obtained using solar cells prepared with the ternary blend. The highest photovoltaic performance of the PBTADN:BantHBT:PC71BM blend solar cells is characterized by a JSC of 11.0 mA cm−2, an open circuit voltage (VOC) of 0.91 V, a FF of 56.4%, and a power conversion efficiency (PCE) of 5.6% under AM1.5G illumination (with a high intensity of 100 mW−2). The effects of the small molecules on the ternary blend are investigated by comparison with the traditional poly(3‐hexylthiophene) (P3HT):[6,6]‐phenyl‐C61‐butyric acid methyl ester (PC61BM) system. Two anthracene‐based star‐shaped conjugated small molecules, HBantHBT and BantHBT, are incorporated into organic photovoltaic cells prepared using a poly((5,5‐E‐alpha‐((2‐thienyl)methylene)‐2‐thiophene acetonitrile‐alt‐2;6‐[(1,5‐didecyloxy) naphthalene])): [6,6]‐phenyl‐C71‐butyric acid methyl ester (PBTADN:PC71BM) blend as a electron‐cascade donor material. The small molecules penetrate the PBTADN:PC71BM blend layer to yield complementary light absorption spectra, facilitate energy level alignment, and optimize the domain size required for charge carrier transfer.