Reducing non-radiative recombination energy loss via a fluorescence intensifier for efficient and stable ternary organic solar cells

Guest Acceptors with Lower Electrostatic Potential in Ternary Organic Solar Cells for Minimizing Voltage Losses

The ternary strategy, in which one guest component is introduced into one host binary system, is considered to be one of the most effective ways to realize high-efficiency organic solar cells (OSCs). To date, there is no efficient method to predict the effectiveness of guest components in ternary OSCs. Herein, three guest compositions (i.e., ANF-1, ANF-2 and ANF-3) with different electrostatic potential (ESP) are designed and synthesized by modulating the electron-withdrawing ability of the terminal groups through density functional theory simulations. The effects of the introduction of guest component into the host system (D18:N3) on the photovoltaic properties are investigated. The theoretical and experimental studies provide a key rule for guest acceptor in ternary OSCs to improve the open-circuit voltage, that is, the larger ESP difference between the guest and host acceptor, the stronger the intermolecular interactions and the higher the miscibility, which improves the luminescent efficiency of the blend film and the electroluminescence quantum yield (EQEEL) of the device by reducing the aggregation-caused-quenching, thereby effectively decreasing the non-radiative voltage loss of ternary OSCs. This work will greatly contribute to the development of highly efficient guest components, thereby promoting the rapid breakthrough of the 20% efficiency bottleneck for single-junction OSCs.

Probing the Effect of Photovoltaic Material on Voc in Ternary Polymer Solar Cells with Non-Fullerene Acceptors by Machine Learning

The power conversion efficiency (PCE) of ternary polymer solar cells (PSCs) with non-fullerene has a phenomenal increase in recent years. However, improving the open circuit voltage (V_oc) of ternary PSCs with non-fullerene still remains a challenge. Therefore, in this work, machine learning (ML) algorithms are employed, including eXtreme gradient boosting, K-nearest neighbor and random forest, to quantitatively analyze the impact mechanism of V_oc in ternary PSCs with the double acceptors from the two aspects of photovoltaic materials. In one aspect of photovoltaic materials, the doping concentration has the greatest impact on V_oc in ternary PSCs. Furthermore, the addition of the third component affects the energy offset between the donor and acceptor for increasing V_oc in ternary PSCs. More importantly, to obtain the maximum V_oc in ternary PSCs with the double acceptors, the HOMO and LUMO energy levels of the third component should be around (-5.7 ± 0.1) eV and (-3.6 ± 0.1) eV, respectively. In the other aspect of molecular descriptors and molecular fingerprints in the third component of ternary PSCs with the double acceptors, the hydrogen bond strength and aromatic ring structure of the third component have high impact on the V_oc of ternary PSCs. In partial dependence plot, it is clear that when the number of methyl groups is four and the number of carbonyl groups is two in the third component of acceptor, the V_oc of ternary PSCs with the double acceptors can be maximized. All of these findings provide valuable insights into the development of materials with high V_oc in ternary PSCs for saving time and cost.

Lifetime over 10000 hours for organic solar cells with Ir/IrOx electron-transporting layer

The stability of organic solar cells is a key issue to promote practical applications. Herein, we demonstrate that the device performance of organic solar cells is enhanced by an Ir/IrOx electron-transporting layer, benefiting from its suitable work function and heterogeneous distribution of surface energy in nanoscale. Notably, the champion Ir/IrOx-based devices exhibit superior stabilities under shelf storing (T80 = 56696 h), thermal aging (T70 = 13920 h), and maximum power point tracking (T80 = 1058 h), compared to the ZnO-based devices. It can be attributed to the stable morphology of photoactive layer resulting from the optimized molecular distribution of the donor and acceptor and the absence of photocatalysis in the Ir/IrOx-based devices, which helps to maintain the improved charge extraction and inhibited charge recombination in the aged devices. This work provides a reliable and efficient electron-transporting material toward stable organic solar cells.

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.

Nonalloy Model-Based Ternary Organic Solar Cells

Ternary blending based on an alloy-like model has been proved as an efficient strategy for high-efficiency organic solar cells (OSCs). However, the third component that possesses excellent miscibility with host materials in the alloy-like model may trigger adverse effects for the active layer, especially at a high doping ratio. In this work, we propose a new concept of nonalloy model for the ternary OSCs in which the third component presents moderate miscibility with the acceptor and distributes at the interspace between donor and acceptor domains. The nonalloy model is constructed based on the PM6:Y6 system, and a Y6 analogue (BTP-MCA) is synthesized as the third component. The BTP-MCA can maintain initial excellent morphology of the active layer and enhance the morphological stability by acting as a frame around the host materials. As a result, ternary OSCs based on the PM6:Y6:BTP-MCA blend exhibit an impressive efficiency of 17.0% with a high open-circuit voltage of 0.87 V. Moreover, the devices present a high doping tolerance (keeping high efficiency with a doping ratio of 50%) and improved stability. This work indicates that the nonalloy model can be a promising method to fabricate efficient and stable ternary OSCs apart from the conventional alloy-like model.