Mengyuan Gao

Bio: Mengyuan Gao is an academic researcher from Tianjin University. The author has an hindex of 1, co-authored 1 publications receiving 2 citations.

The renaissance of polythiophene organic solar cells

Abstract: The past decade has witnessed tremendous advances in the power conversion efficiency (PCE) of organic photovoltaic cells. Concomitantly, the chemical structures of present high-efficiency photovoltaic polymers have become more complex, leading to tedious and harsh synthetic processes and high batch-to-batch variations. By comparison, polythiophenes have gained considerable traction and hold tremendous promise in terms of cost and scalability. In this review, we present state-of-the-art developments in polythiophene solar cells, with a focus on those made of poly(3-hexylthiophene) (P3HT) and nonfullerene small-molecule acceptors. First, the structural optimization of polythiophenes is briefly discussed. Then, we provide a concise discussion of two notable aspects (miscibility matching and crystallization control) for performance optimization and associated research highlights in the past 5 years. We also highlight guidelines to ascertain the scientific challenges for polythiophene:nonfullerene solar cells. The development of new polythiophenes and their bulk-heterojunction blends will help to stimulate advances in many kinds of cost-effective electronics.

Morphology control in <scp>high‐efficiency all‐polymer</scp> solar cells

Abstract: All-polymer solar cells (All-PSCs) have attracted tremendous research interest in the recent decade due to the great potentials in stretchable electronic applications in terms of long-term stability and mechanical stretchability. Driven by the molecular design of novel polymer acceptors and morphology optimization, the power conversion efficiency (PCE) of All-PSCs has developed rapidly and now exceeded 17%. This review outlines the promising strategies for high-performance All-PSCs from the aspect of morphology control with the motivation to rationally guide the optimization. In this review, we briefly discuss the thermodynamic mixing principles of all-polymer blends and the effects of the molecular structure of conjugated polymers on thin-film morphology in All-PSCs. The crucial role of molecular miscibility in influencing morphological features and performance metrics was highlighted. We also expound on the effective methods of controlling film morphology through properly tuning the aggregation behavior of polymers. In particular, insightful studies on the commonly used naphthalene diimide-based acceptor polymers and the newly emerging polymerized nonfullerene small molecule acceptors (ITIC-series, Y6 -series, etc) are discussed in detail. Finally, we present an outlook on the major challenges and the new opportunities of All-PSCs for efficiency breakthroughs targeting 20%.

Unraveling the Molar Mass Dependence of Shearing‐Induced Aggregation Structure of a High‐Mobility Polymer Semiconductor

Abstract: Aggregation-structure formation of conjugated polymers is a fundamental problem in the field of organic electronics and remains poorly understood. Herein, the molar mass dependence of the aggregation structure of a high-mobility conjugated copolymer (TDPP-Se) comprising thiophene-flanked diketopyrrolopyrrole and selenophene is thoroughly shown. Five batches of TDPP-Se are prepared with the number-average molecular weights (Mn ) varied greatly from 21 to 135 kg mol-1 . Small-angle neutron scattering and transmission electron microscopy are combined to probe the solution structure of these polymers, consistently using a deuterated solvent. All the polymers adopt 1D rod-like aggregation structures and the radius of the 1D rods is not sensitive to the Mn , while the length increases monotonically with Mn . By utilizing the ordered packing of the aggregated structure in solution, a highly aligned and ordered film is prepared and, thereafter, a reliable hole mobility of 13.8 cm2 V-1 s-1 is realized in organic thin-film transistors with the moderate Mn batch via bar coating. The hole mobility is among the highest values reported for diketopyrrolopyrrole-based polymers. This work paves the way to visualize the real aggregated structure of polymer semiconductors in solution and sheds light on the microstructure control of high-performance electronic devices.

Towards a bright future: The versatile applications of organic solar cells

Abstract: Due to the mechanical flexibility, light weight, aesthetics, absorption tunability and environmental friendliness, organic solar cells (OSCs) have superior application potential over their inorganic counterparts including silicon and perovskite solar cells (PSCs). Thanks to these benefits, the past decade have witnessed the rapid growth of flexible OSCs, semitransparent OSCs and indoor OSCs. In this progress report, we firstly overview the recent advance of the applications of the three promising OSCs. Subsequently, we sketch the critical points for the three classes of OSCs and highlight the efforts paid by the research community to address these issues. Besides, we discuss some popular strategies to afford great performance of each kind of OSC, respectively, and underline the corresponding breakthrough directions. Last but not least, we present the remaining challenges for advancing the commercial applications of these three classes of OSCs.

An Aggregation-Suppressed Polymer Blending Strategy Enables High-Performance Organic and Quantum Dot Hybrid Solar Cells.

Abstract: Solution-processing hybrid solar cells with organics and colloidal quantum dots (CQDs) have drawn substantial attention in the past decade. Nevertheless, hybrid solar cells based on the recently developed directly synthesized CQD inks are still unexplored. Herein, a facile polymer blending strategy is put forward to enable directly synthesized CQD/polymer hybrid solar cells with a champion efficiency of 13%, taking advantage of the conjugated polymer blends with finely optimized aggregation behaviors. The spectroscopic and electrical investigations on carrier transport and recombination indicate that polymer blends can endow fast carrier transport and less recombination over the single counterparts. Moreover, the blending strategy offers a "dilution effect" for top-notch photovoltaic polymers with excessively strong aggregation tendency, resulting in moderate feature domain size and surface roughness, which afford fast hole transport and therefore high photovoltaic performance. The effectiveness of this strategy is successfully validated using two pairs of photovoltaic polymers. Accordingly, the relationships between polymer morphology, carrier transport, and photovoltaic performance are established to advance the progress of CQD/polymer hybrid solar cells. Such progress stresses that the utilization of aggregation-suppressed polymer blends is a facile approach toward the fabrication of high-efficiency organic-inorganic hybrid solar cells.