Lik-Kuen Ma

The Hong Kong University of Science and Technology | UST · Department of Chemistry

In this work, we attempt to figure out alkoxy-substitution effects on two kinds of well-known non-fullerene acceptors (NFAs), IDT-series and Y-series acceptors, by placing alkoxy side chains on the β-positions of the outer thiophene units. The resulting molecules, namedIDTN-OandY6-O, exhibit different properties compared to the original acceptors n...

In this paper, a strategy of asymmetric alkyl and alkoxy substitution is applied to state‐of‐the‐art Y‐series nonfullerene acceptors (NFAs), and it achieves great performance in organic solar cell (OSC) devices. Since alkoxy groups can have a significant influence on the material properties of NFAs, alkoxy substitution is applied to the Y6 molecule...

It is widely known that the miscibility between donor and acceptor is a crucial factor that affects the morphology and thus device performance of non-fullerene organic solar cells (OSCs). In this paper, we show that incorporating a third component with lower miscibility and higher LUMO level into state-of-the-art PM6:Y6 system can significantly enh...

Although the field of all‐polymer solar cells (all‐PSCs) has seen rapid progress in device efficiencies during the past few years, there are limited choices of polymer acceptors that exhibit strong absorption in the near‐IR region and achieve high open‐circuit voltage (VOC) at the same time. In this paper, an all‐PSC device is demonstrated with a 1...

Organic indoor light harvesters require large‐area active layers for power‐greedy internet of thing (IoT) things due to much weaker light emissions from indoor sources than the standard 1‐Sun case. This presents new challenges for the thick‐film indoor photovoltaic (IPV) device fabrication to meet the requirements of current leading roll‐to‐roll (R...

The emergence of indoor electronic devices for internet of things (IoT) has motivated the scientific community to develop photovoltaic devices that can efficiently convert indoor light into electricity. In this paper, we report high-efficiency non-fullerene organic photovoltaic (OPV) cells with over 30% power conversion efficiency (PCE) under indoo...

Core engineering of small molecule acceptors (SMAs) is crucially important for enhancing device efficiency for nonfullerene organic solar cells (NF-OSCs). The most commonly used SMAs (e.g., ITIC) utilize indacenodithieno[3,2-b]thiophene (IDTT) as the central core, which has restricted their absorption ranges due to the weak electron-donating abilit...

Conventional organic solar cell (OSC) systems have significant energy offsets between the donor and acceptor both at the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels. Because of this, in a bulk heterojunction (BHJ) system, electrons typically transport in acceptors, whereas holes typically t...

Generally, the electron-withdrawing substitution on the end-capping group of the acceptor-donor-acceptor type small-molecule acceptor (SMA) narrows the optical bandgap and that the electron-donating group lifts the lowest unoccupied molecular orbital (LUMO) energy level of non-fullerene SMA, which increase the short-circuit current density (JSC) an...

Reducing the voltage loss is considered a promising route to improve the performance of organic solar cells (OSCs). In this work, two donor polymers PT4FB and PTT4FB based on the tetra-fluorinated benzene building block are synthesized and applied to non-fullerene OSC devices, which achieve high open-circuit voltage (VOC). When PT4FB is combined wi...

Two novel perylene diimide tetramer-based non-fullerene acceptors, PDIPQ-C5 and PDIPQ-C6, with different alkyl chain length were synthesized. Side-chain effects were studied by theoretical calculation, grazing incident X-ray diffraction, and atomic...

To minimize the voltage loss of non-fullerene organic solar cells (OSCs), it is important to modulate the energy levels of active materials and thus the photovoltage of the device. In this paper, we report a simple and effective approach to tune the energy levels of a state-of-art polymer P3TEA by switching the position of alkyl side chains and car...

Compared to the rapid development of nonfullerene organic solar cells (OSCs) based on the state‐of‐the‐art indacenodithiophene (IDT)‐based small molecule acceptors (SMAs), the progress for perylene diimide (PDI)‐based electron acceptors has lagged behind owing to the lack of understanding on the structure–morphology–performance relationship of PDI...

Carboxylate substitution is a common approach to tune the energy level of donor polymers for organic solar cells. However, the influence of carboxylate substitution on the morphological and electronic properties of donor polymers is not well understood. In this paper, we study two pairs of structurally similar terthiophene or quarterthiophene donor...

Non-fullerene organic solar cells (NF-OSCs) require donor polymers with different morphological properties from those used in fullerene devices to achieve optimal cell performance. In this paper, we report a random donor polymer (PTFB-M) constructed from an asymmetric donor unit (T-FB-T-M), which can effectively tune the morphology and thus enhance...

Fullerene-based bulk heterojunction organic solar cells (BHJ-OSCs) represent one of the current state-of-the-art organic solar cells. Nonetheless, most of these devices still suffer from adverse performance degradation due to thermally induced morphology changes of active layers. We herein demonstrate that the photovoltaic performance stability of...