Near‐Infrared Nonfullerene Acceptors Based on Benzobis(thiazole) Unit for Efficient Organic Solar Cells with Low Energy Loss

Abstract

The simultaneous achievement of a low energy loss and high external quantum efficiency (EQE) response is the prerequisite for high power conversion efficiencies of organic solar cells (OSCs). Herein, this issue is examined through the design of two novel near‐infrared (NIR) nonfullerene acceptors (X‐PCIC and X1‐PCIC) with an absorption extending to 900 nm, which is realized by using benzobis(thiazole) unit as the core. This study reveals that benzobis(thiazole) unit with the quinoid‐resonance effect and electron‐withdrawing property is a good building block in extending absorption and maintaining suitable energy levels. Single crystal cultivation proves the function of S···N noncovalent interaction in locking molecular geometry. Besides, through adopting two different terminals (fluorinated terminal for X‐PCIC and thiophene‐fused terminal for X1‐PCIC), it is found that an increase in the J‐aggregation strength has a significant positive effect on the EQE response of the devices through the formation of more suitable domain sizes and crystallinity in the films, while the energy loss remains low (≈0.53 eV) and unaffected. Thus, a high efficiency of 11.50% is presented for OSC based on the X‐PCIC with stronger J‐aggregation strength, better than that (10.17%) based on the X1‐PCIC with weaker J‐aggregation strength. This work clearly demonstrates the application of benzobis(thiazole) unit in efficient small molecule acceptors and the importance of J‐aggregation modulation for the simultaneous achievement of low energy loss and high EQE response.

Novel cost-effective acceptor:P3HT based organic solar cells exhibiting the highest ever reported industrial readiness factor

“…voltage loss. [29][30][31] The film absorption ( Fig. 1D) for all four materials exhibit red-shifts in their onset in a range of 29-42 nm, however, whereas A1 and A4 presents a l Max red-shift of 16 nm, A2 and A3 have slight blue-shifts in l Max of 13 and 17 nm, respectively, which implies a hinderance in p-p stacking likely due to the steric twists within the molecules.…”

An A-D-A′-D-A type unfused nonfullerene acceptor for organic solar cells with approaching 14% efficiency

“…For the design of UFAs, the selection of A′ (and D′) unit is a key issue, which is essential for regulating energy levels, light-harvest ability, intramolecular interactions, and intermolecular packing behavior. At present, many research groups have done a lot of meaningful work on the selection of A′ (and D′) units, such as para-difluorobenzene [7], para-dialkoxybenzene [9], benzobis(thiazole) [14], 5,6dialkoxy-substituted benzothiadiazole [17], 3,4-difluorothiophene [8], and thieno [3,4-c]pyrrole-4,6-dione [20]. However, the PCEs of UFAs have still lagged far behind those of FRAs.…”

High‐Performance Semi‐Transparent Organic Photovoltaic Devices via Improving Absorbing Selectivity

“…In the past few years, non-fullerene acceptor (NFA) showed promise to achieve high device performance with strong absorption in NIR region. [26][27][28][29][30][31] The success of low band gap NFA also catalyzed rapid development of ST-OPVs, owing to their good selective absorption. For example, NFA materials such as IEICO-4F, IUIC, FOIC, etc., showed good NIR absorbing and visible transmission properties, and the corresponding ST-OPVs delivered PCE of 10.03% and LUE of 3.43% when blended with PTB7-Th.…”