Junfeng Tong

Bio: Junfeng Tong is an academic researcher from Lanzhou Jiaotong University. The author has contributed to research in topics: Polymer solar cell & Materials science. The author has an hindex of 17, co-authored 58 publications receiving 766 citations.

The comprehensive utilization of the synergistic effect of fullerene and non-fullerene acceptors to achieve highly efficient polymer solar cells

Abstract: A ternary strategy could combine the advantages of incorporated materials as an encouraging approach to achieve high power conversion efficiency (PCE) polymer solar cells (PSCs). In this work, ternary PSCs based on PTBTz-2:IT-M:PC71BM with different weight ratios were systematically investigated. With 20 wt% PC71BM incorporated into the accepters, the PSCs achieved the best PCE as high as 12.28% with an open-circuit voltage (VOC) of 0.928 V, a short-circuit current density (JSC) of 18.70 mA cm−2 and a fill factor (FF) of 70.78%, which is undoubtedly superior to those of binary devices based on PTBTz-2:IT-M (10.39%) or PTBTz-2:PC71BM (9.20%). The energy transfer mechanism between PC71BM and IT-M was investigated in depth by femtosecond pump–probe transient absorption spectroscopy and time-correlated single-photon counting. The Forster resonance energy transfer mechanism between PC71BM and IT-M has been powerfully verified. Morphology characterization analysis, density of states theory and density functional theory calculations indicated that the excellent combination of PC71BM and IT-M has a synergistic effect on the VOC values of the devices. Our results suggested that the two acceptors with drastically different structures could synergistically combine the merits of each to optimize crystallinity and charge generation, separation, and collection, which simultaneously enhanced the PCEs.

Enhanced efficiency of polymer solar cells through synergistic optimization of mobility and tuning donor alloys by adding high-mobility conjugated polymers

Abstract: A diketopyrrolopyrrole-based small bandgap polymer (DPPT-TT) with high mobility is introduced as an additive to D–A1–D–A2 type thieno[3,4-b]thiophene-based random copolymer (P3):(6,6)-phenyl-C70-butyric acid methyl ester (PC71BM) polymer solar cells (PSCs) The average power conversion efficiencies (PCEs) were improved from 615% to 830% with the addition of 05% DPPT-TT The photocurrent density versus effective voltage (Jph–Veff) curves, short-circuit current density (JSC) and open circuit voltage (VOC) as functions of incident light intensity, photoluminescence (PL) and time-resolved transient PL (TRTPL) spectra were investigated, and the results certified the effect of DPPT-TT as the third component material in terms of efficient exciton dissociation and weakened charge carrier recombination The relationship between VOC and the weight ratio of DPPT-TT was explained with density functional theory (DFT) calculations and the electron density of states of unit mass (Ne), indicating the formation of a polymer alloy in ternary blend With proper addition of DPPT-TT, the mobility of electrons and holes becomes more balanced and the efficiency of exciton utilization is improved due to the existence of Forster resonance energy transfer (FRET), which also contributes to the enhanced JSC and PCEs Our work demonstrates that appropriate donor polymers forming a polymer alloy in blend is a rational strategy to improve photovoltaic performance

Enhanced Organic Photovoltaic Performance through Modulating Vertical Composition Distribution and Promoting Crystallinity of the Photoactive Layer by Diphenyl Sulfide Additives.

Abstract: To understand the vertical phase separation in the bulk junction active layer of organic photovoltaic devices is essential for controlling the charge transfer behavior and achieving effective charge collection. Here, diphenyl sulfide (DPS) was introduced as a novel additive into the PTB7-Th:PC71BM-based inverted polymer solar cells (PSCs), and the effect of additives on active blend films and photovoltaic characteristics was carefully studied. The results show that DPS could not only modulate the vertical composition distribution but also promote the ordered molecular packing of the photoactive layer, thus effectively improving exciton dissociation, charge transport, and collection, and thus exhibit an excellent power conversion efficiency of 9.7% with an improved fill factor (>70%) after using 3% DPS additive. The results show that the DPS solvent additive can effectively adjust the vertical phase distribution and crystallinity of blend films and improve the photovoltaic performance of the inverted organ...

Insights into Excitonic Dynamics of Terpolymer-Based High-Efficiency Nonfullerene Polymer Solar Cells: Enhancing the Yield of Charge Separation States

Abstract: Ternary copolymerization strategy is considered an effective method to achieve high-performance photovoltaic conjugated polymers. Herein, a donor–acceptor1–donor–acceptor2-type random copolymer, na...

Non-toxic green food additive enables efficient polymer solar cells through adjusting the phase composition distribution and boosting charge transport

Abstract: Solvent additives play an important role in optimizing the morphology of the photoactive layer and improving the photovoltaic performance of polymer solar cells (PSCs). However, the toxicity of common additives to the environment limits their further application in photovoltaic cells. Herein, a non-toxic green food additive, benzyl salicylate (BS), was introduced as a novel solvent additive into inverted PSCs based on ITO/ZnO/PTB7-Th:PC71BM/MoO3/Ag. Subsequently, the effect of BS on the photovoltaic performance was studied, and the best power conversion efficiency (PCE) of 9.43% was achieved when adding 2% BS into the photoactive layer of PSCs. Furthermore, the PSCs treated by 1–4% BS all exhibited good photovoltaic performance compared to that using 3% DIO (8.56%), which demonstrated that the universality was very strong. In addition, a good solubility for fullerenes was presented on BS like DIO, which was determined by atomic force microscopy and transmission electron microscopy. The water contact angle and time-off flight secondary ion mass spectroscopy results manifested that the good solubility of high-boiling-point additive BS to PC71BM could boost the phase composition distribution at the surface and in the vertical direction. Thus, an efficient route for exciton dissociation and charge transfer could be formed when the PSC was processed via 2% BS, which could also be ascertained by space charge limited current, impedance spectroscopy. The present research findings provide useful information for realizing large-area PSC fabrication, where a greener non-toxic additive is always preferred.

Stability of polymer solar cells.

Abstract: Organic photovoltaics (OPVs) evolve in an exponential manner in the two key areas of efficiency and stability. The power conversion efficiency (PCE) has in the last decade been increased by almost a factor of ten approaching 10%. A main concern has been the stability that was previously measured in minutes, but can now, in favorable circumstances, exceed many thousands of hours. This astonishing achievement is the subject of this article, which reviews the developments in stability/degradation of OPVs in the last five years. This progress has been gained by several developments, such as inverted device structures of the bulk heterojunction geometry device, which allows for more stable metal electrodes, the choice of more photostable active materials, the introduction of interfacial layers, and roll-to-roll fabrication, which promises fast and cheap production methods while creating its own challenges in terms of stability.

Molecular Design of Benzodithiophene-Based Organic Photovoltaic Materials.

Abstract: Advances in the design and application of highly efficient conjugated polymers and small molecules over the past years have enabled the rapid progress in the development of organic photovoltaic (OPV) technology as a promising alternative to conventional solar cells. Among the numerous OPV materials, benzodithiophene (BDT)-based polymers and small molecules have come to the fore in achieving outstanding power conversion efficiency (PCE) and breaking 10% efficiency barrier in the single junction OPV devices. Remarkably, the OPV device featured by BDT-based polymer has recently demonstrated an impressive PCE of 11.21%, indicating the great potential of this class of materials in commercial photovoltaic applications. In this review, we offered an overview of the organic photovoltaic materials based on BDT from the aspects of backbones, functional groups, alkyl chains, and device performance, trying to provide a guideline about the structure-performance relationship. We believe more exciting BDT-based photovol...

Recent advances in water/alcohol-soluble π-conjugated materials: new materials and growing applications in solar cells

Abstract: Water/alcohol-soluble conjugated polymers (WSCPs) and small molecules (WSCSs) are materials that can be processed from water or other polar solvents. They provide good opportunities to fabricate multilayer organic optoelectronic devices without interface mixing by solution processing, and exhibit a promising interface modification ability for metal or metal oxide electrodes to greatly enhance the device performance of solar cells. Moreover, owing to their intriguing processability, WSCPs and WSCSs have great potential for applying environmentally friendly processing technologies to fabricate solar cells. In this review, the authors give an overview of recent developments in WSCPs and WSCSs, including their molecular design, material synthesis, functional principles and application as interface modification layers and photoactive components in emerging photovoltaic technologies such as organic/polymer solar cells, organic–inorganic hybrid solar cells and dye-sensitised solar cells.