Manipulating molecular orientation at the donor/acceptor interface is the key to boosting charge separation properties and efficiencies of anisotropic‐materials‐based organic photovoltaics (OPVs). By ...replacing the polymeric donor PBDTBDD with its 2D‐conjugated polymer PBDTBDD‐T, the power conversion efficiency of OPVs featuring the anisotropic polymer acceptor PNDI is drastically boosted from 2.4% up to 5.8%.
Binary additives synergistically boost the power conversion efficiency of all-polymer solar cells up to 3.45%. The nonvolatile additive PDI-2DTT suppresses aggregation of the acceptor PPDIDTT and ...enhances donor/acceptor mixing, while the additive DIO facilitates aggregation and crystallization of the donor PBDTTT-C-T as well as improves phase separation. Combination of DIO and PDI-2DTT leads to suitable phase separation and improved and balanced charge transport, which is beneficial to efficiency enhancement.
The mixed solvent approach has been demonstrated as a promising method to modify nanomorphology in polymer solar cells. This work aims to understand the unique role of the additive in the mixture ...solvent and how the optimized nanoscale phase separation develops laterally and vertically during the non‐equilibrium spin‐coating process. We found the donor/acceptor components in the active layer can phase separate into an optimum morphology with the additive. Supported by AFM, TEM and XPS results, we proposed a model and identified relevant parameters for the additive such as solubility and vapor pressures. Other additives are discovered to show the ability to improve polymer solar cell performance as well.
The evolution of nanoscale phase separation in polymer:fullerene solar cells with mixture solvents is discussed. Optimum morphology is formed both laterally and vertically during spin‐coating with better device performance. Supported by AFM, TEM, and XPS results, we proposed a model and identified relevant parameters for the additive, such as solubility and vapor pressure.
Nonhalogenated polymers have great potential in the commercialization of organic photovoltaic (OPV) cells due to their advantage in low‐cost preparation. However, non‐halogenated polymers usually ...have high highest occupied molecular orbital (HOMO) energy levels and inferior self‐aggregation properties in solution, thus resulting in low power conversion efficiencies (PCEs). Herein, two nonhalogenated polymers, PB1 and PB2, are prepared. When the polymers are used to fabricate OPV cells with BTP‐eC9, the PB1‐based device only gives a PCE of 5.3%, while the PB2‐based device shows an outstanding PCE of 17.7%. After the introduction of PBDB‐TF as the third component, the PB2:PBDB‐TF:BTP‐eC9‐based device with an optimal weight ratio of 0.5:0.5:1 achieves a PCE up to 18.4%. More importantly, PB2 exhibits good compatibility with various nonfullerene acceptors to achieve better PCEs than those of classical polymer (PBDB‐T and PBDB‐TF)‐based devices. When PB2 is combined with a wide‐bandgap electron acceptor (F‐BTA3), this device shows excellent PCE of 27.1% and 24.6% for 1 and 10 cm2 devices, respectively, under light intensity of 1000 lux light‐emitting diode illumination. These results provide new insight in the rational design of novel nonhalogenated polymer donors for further development of low‐cost materials and broadening the application of OPV cells.
Two nonhalogenated polymers, PB1 and PB2, with different side‐chain orientations and deep highest occupied molecular orbital (HOMO) levels are reported. In organic photovoltaic (OPV) cells, PB1 only produces a power conversion efficiency (PCE) of 5.3%, while PB2 gives an outstanding PCE of 17.7%. More importantly, PB2 has good compatibility with various electron acceptors. PB2 achieves excellent PCEs of 18.4% and 27.1% for ternary OPV cells and indoor light photovoltaic devices, respectively.
Decreasing the energy loss is one of the most feasible ways to improve the efficiencies of organic photovoltaic (OPV) cells. Recent studies have suggested that non‐radiative energy loss (Enon-radloss
...) is the dominant factor that hinders further improvements in state‐of‐the‐art OPV cells. However, there is no rational molecular design strategy for OPV materials with suppressed Enon-radloss
. Herein, taking molecular surface electrostatic potential (ESP) as a quantitative parameter, we establish a general relationship between chemical structure and intermolecular interactions. The results reveal that increasing the ESP difference between donor and acceptor will enhance the intermolecular interaction. In the OPV cells, the enhanced intermolecular interaction will increase the charge‐transfer (CT) state ratio in its hybridization with the local exciton state to facilitate charge generation, but simultaneously result in a larger Enon-radloss
. These results suggest that finely tuning the ESP of OPV materials is a feasible method to further improve the efficiencies of OPV cells.
Non‐radiative energy loss in organic photovoltaic cells can be achieved by tuning the charge‐transfer state ratio in the hybridized state with the local exciton state. The molecular electrostatic potential (ESP) is considered as a quantitative parameter. By adjusting the ESP difference between PBDB‐TF and BTP‐XF, non‐radiative energy loss is reduced from 0.23 to 0.15 eV.
π‐Conjugated organic/polymer materials‐based solar cells have attracted tremendous research interest in the fields of chemistry, physics, materials science, and energy science. To date, the ...best‐performance polymer solar cells (PSCs) have achieved power conversion efficiencies exceeding 18%, mostly driven by the molecular design and device structure optimization of the photovoltaic materials. This review article provides a comprehensive overview of the key advances and current status in aggregated structure research of PSCs. Here, we start by providing a brief tutorial on the aggregated structure of photovoltaic polymers. The characteristic parameters at different length scales and the associated characterization techniques are overviewed. Subsequently, a variety of effective strategies to control the aggregated structure of photovoltaic polymers are discussed for polymer:fullerene solar cells and polymer:nonfullerene small molecule solar cells. Particularly, the control strategies for achieving record efficiencies in each type of PSCs are highlighted. More importantly, the in‐depth structure–performance relationships are demonstrated with selected examples. Finally, future challenges and research prospects on understanding and optimizing the aggregated structure of photovoltaic polymers and their blends are provided.
A comprehensive overview of the key advances and current status in aggregated structure research of photovoltaic polymers was presented. This review provided a tutorial on the multi‐level aggregated structure and the characteristic parameters as well as the associated characterization techniques. To in‐depth understand the structure‐performance relationships, effective strategies to control the aggregated structure of photovoltaic polymers are summarized, with an emphasis on the systems of record‐high power conversion efficiencies.
Two p-type conjugated polymers with disparate optical and electronic properties, PB3T and PB2T, were developed and applied in fullerene-free polymer solar cells (PSCs). The photovoltaic performance ...of the PB3T-based PSC device processed by anisole achieved a high power conversion efficiency of 11.9% with a Jsc of 18.8 mA cm-2 and Voc of 1.00 V.
Acceptor alloys based on n‐type small molecular and fullerene derivatives are used to fabricate the ternary solar cell. The highest performance of optimized ternary device is 10.4%, which is the ...highest efficiency for one donor/two acceptors‐based ternary systems. Three important parameters, JSC, VOC, and FF, of the optimized ternary device are all higher than the binary reference devices.
A new low band gap silole-containing conjugated polymer, PSBTBT, was designed and synthesized. Photovoltaic properties of PSBTBT were initially investigated, and an average power conversion ...efficiency (PCE) of 4.7 % with a best PCE of 5.1 % was recorded under illumination (AM 1.5G, 100 mW/cm2). The response range of the device covers the whole visible range from 380 to 800 nm. These results indicate that PSBTBT is a promising polymer material for applications in polymer solar cells.
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