A Simple Dithieno[3,2-b:2',3'-d]pyrrol-Rhodanine Molecular Third Component Enables Over 16.7% Efficiency and Stable Organic Solar Cells

Tailoring the Molecular Planarity of Perylene Diimide-Based Third Component toward Efficient Ternary Organic Solar Cells

Incorporating a third component into binary organic solar cells (b-OSCs) has provided a potential platform to boost power conversion efficiency (PCEs). However, gaining control over the non-equilibrium blend morphology via the molecular design of the perylene diimide (PDI)-based third component toward efficient ternary organic solar cells (t-OSCs) still remains challenging. Herein, two novel PDI derivatives are developed with tailored molecular planarity, namely ufBTz-2PDI and fBTz-2PDI, as the third component for t-OSCs. Notably, after performing a cyclization reaction, the twisted ufBTz-2PDI with an amorphous character transferred to the highly planar fBTz-2PDI followed by a semi-crystalline character. When incorporating the semi-crystalline fBTz-2PDI into the D18:L8-BO system, the resultant t-OSC achieved an impressive PCE of 18.56%, surpassing the 17.88% attained in b-OSCs. In comparison, the addition of amorphous ufBTz-2PDI into the binary system facilitates additional charge trap sites and results in a deteriorative PCE of 14.37%. Additionally, The third component fBTz-2PDI possesses a good generality in optimizing the PCEs of several b-OSCs systems are demonstrated. The results not only provided a novel A-DA'D-A motif for further designing efficient third component but also demonstrated the crucial role of modulated crystallinity of the PDI-based third component in optimizing PCEs of t-OSCs.

Stability of organic solar cells: toward commercial applications

Organic solar cells (OSCs) have attracted a great deal of attention in the field of clean solar energy due to their advantages of transparency, flexibility, low cost and light weight. Introducing them to the market enables seamless integration into buildings and windows, while also supporting wearable, portable electronics and internet-of-things (IoT) devices. With the development of photovoltaic materials and the optimization of fabrication technology, the power conversion efficiencies (PCEs) of OSCs have rapidly improved and now exceed 20%. However, there is a significant lack of focus on material stability and device lifetime, causing a severe hindrance to commercial applications. In this review, we carefully review important strategies employed to improve the stability of OSCs over the past three years from the perspectives of material design and device engineering. Furthermore, we analyze and discuss the current important progress in terms of air, light, thermal and mechanical stability. Finally, we propose the future research directions to overcome the challenges in achieving highly stable OSCs. We expect that this review will contribute to solving the stability problem of OSCs, eventually paving the way for commercial applications in the near future.

Achieved 18.9% Efficiency by Fine-Tuning Non-Fullerene Acceptor Content to Simultaneously Increase the Short-Circuit Current and Fill Factor of Organic Solar Cells

In this study, using PM6:L8-BO as the main system and non-fullerene acceptor IDIC as the third component, a series of ternary organic solar cells (TOSCs) are fabricated. The results reveal that IDIC plays a significant role in enhancing the performance of TOSCs by optimizing the morphology of blended films and forming interpenetrating nanostructure. The improved film morphology facilitates exciton dissociation and collection in TOSCs, which causes an increase in the short-circuit current density (JSC ) and fill factor (FF). Further, by optimizing the IDIC content, the power conversion efficiency (PCE) of TOSCs reaches 18.9%. Besides, the prepared TOSCs exhibit a JSC of 27.51 mA cm-2 and FF of 76.64%, which are much higher than those of PM6:L8-BO-based organic solar cells (OSCs). Furthermore, the addition of IDIC improves the long-term stability of the OSCs. Meanwhile, TOSCs with a large effective area of 1.00 cm2 have been prepared, which exhibit a PCE of 12.4%. These findings suggest that modifying the amount of the third component can be a useful strategy to construct hight-efficiency TOSCs with practical application potential.

Ternary Blend Organic Solar Cells: Understanding the Morphology from Recent Progress

Ternary blend organic solar cells (TB-OSCs) incorporating multiple donor and/or acceptor materials into the active layer have emerged as a promising strategy to simultaneously improve the overall device parameters for realizing higher performances than binary devices. Whereas introducing multiple materials also results in a more complicated morphology than their binary blend counterparts. Understanding the morphology is crucially important for further improving the device performance of TB-OSC. This review introduces the solubility and miscibility parameters that affect the morphology of ternary blends. Then, this review summarizes the recent processes of morphology study on ternary blends from the aspects of molecular crystallinity, molecular packing orientation, domain size and purity, directly observation of morphology, vertical phase separation as well as morphological stability. Finally, summary and prospects of TB-OSCs are concluded.

Recent Progress in Indacenodithiophene-Based Acceptor Materials for Non-Fullerene Organic Solar Cells

Domesticating solar energy by exploiting photovoltaic technology has become a quintessential strategy for future global energy production. Since 2015, non-fullerene organic solar cells (NF-OSC) have attracted a great deal of attention owing to the marvellous properties of non-fullerene acceptors (NFA) such as structural versability, broad absorption, suitable energy levels, tunable charge transport and morphology, leading to remarkable accomplishments in power conversion efficiency (PCE) from 1% to nearly 20%. One class of materials is provided by the fused ring aromatic indacenodithiophene (IDT) and its derivatives, which are emerging continuously as promising next-generation building blocks to construct high performance photovoltaic materials. Encouraging PCEs of more than 15% have been achieved in their binary NF-OSCs, while careful device engineering and proper amalgamation of a third component have led to PCEs of almost 18% in ternary devices. This review surveys recent developments in the area of IDT-based materials for photovoltaic applications. Different strategies to develop efficient IDT-based NFA and factors influencing the bandgaps, molecular energy levels, charge transport properties, and film morphologies, as well as the photovoltaic performance of these materials, are discussed.