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

Abstract

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.

Bridging donor–acceptor energy offset using organic dopants as energy ladders to improve open-circuit voltages in bulk-heterojunction solar cells

“…The current approaches for cell architecture improvement include the use of a mix solvent for interfacial morphology control, the incorporation of additives that obtain proper molecular orientation, the formation of a cascade energy structure to cover more solar spectra with ternary blend, and the addition of metal nanostructures to enhance absorption via the excited surface plasmon. These cell architecture methods have mainly been investigated for complementary absorption and better utilization of the solar radiation spectrum, particularly for improving the short-circuit current density (J sc ) of the BHJ solar cells [15][16][17][18][19][20]. However, the correlation between dopant and consequent V oc enhancement is still ambiguous and rarely discussed.…”

Perspective of a new trend in organic photovoltaic: ternary blend polymer solar cells

“…The cascade like energy levels (shown in Fig. 4) of ternary blend PSCs can facilitate charge transfer at the D/A interface owing to the bridging effect to reduce the energy loss [31,32]. For example, Huang et al [33] reported that by incorporating a small molecule donor 7,7'-{5,5'- [10,12-…”

“…Cha et al [31] developed a naphthalene derivative polymer donor material, PBTADN, and the acceptor material, PC 71 BM, were blended with either of two different anthracene-based star-shaped conjugated small molecules, HBantHBT and BantHBT, which provided intermediate energy levels to produce a ternary cascade energy structure. The cascade structure effects of the star-shaped conjugated small molecules were examined in a P3HT:PC 61 BM blend system.…”

Morphological Control Agent in Ternary Blend Bulk Heterojunction Solar Cells

“…Among these additives, the fullerene derivatives take the majority due to its compatibility with host acceptors as well as the established solvent systems, though there were other small molecules that revealed a similar function [53][54][55]. Herein we focus on the development of a variety of kinds of fullerene derivatives as morphological control agents.…”