Project team of Professor Peng Qiang of Sichuan University: wide band gap polymer donor based on naphthalene dithiophene and its high efficiency, low energy loss non fullerene solar cells

The introduction polymer solar cell has many outstanding advantages, such as low cost, light weight, large-scale solution preparation of flexible devices, etc it has been widely concerned by academia and industry With the continuous development of new materials and new device technology, the photoelectric conversion efficiency of polymer solar cells has made a continuous breakthrough In recent years, it has become a research hotspot to replace the traditional fullerene materials with non fullerene receptor materials The photoelectric conversion efficiency of organic solar cells based on the blend of non fullerene receptor materials and polymer donors has exceeded 16% To further improve the photoelectric conversion efficiency, we need to reduce the mutual restriction between the open circuit voltage and the short circuit current density However, it is still a challenge to reduce the energy loss (increase the open circuit voltage) and ensure sufficient charge driving force (increase the short circuit current density) More reasonable design of receptor materials is the key to solve the above contradictions Recently, Professor Peng Qiang's research group of Sichuan university designed and synthesized a wide band gap polymer based on naphthalene dithiophene for the preparation of high efficiency and low energy loss non fullerene organic solar cells (DOI: 10.1002 / ADFM 201907570) Prof Peng Qiang, Professor of School of chemistry, Sichuan University, fixed member of National Key Laboratory of polymer materials engineering, doctoral supervisor He has successively won the national outstanding youth fund, the Ministry of education's outstanding talents in the new century, the Sichuan thousand talents program, the academic and technical leaders of Sichuan Province, and the Sichuan outstanding youth fund It is mainly engaged in the molecular design and synthesis of organic small molecules and polymer solar cell key materials (donor, acceptor, interface materials) and the research and development of new process of organic solar cell devices In recent years, more than 150 academic papers have been published in energy energy SCI., adv mater., J am Chem SOC., adv energy mater., adv funct Mater., nano energy, ACS Nano and other domestic and foreign journals, more than 120 papers have been included in SCI, and 33 papers with impact factors greater than 10.0 have been cited by others for more than 4000 times He has written 2 chapters of academic monograph, applied for 18 Chinese invention patents (10 have been authorized), and won 1 provincial and ministerial Natural Science Award (ranking 1) Cutting edge research achievements: a wide band gap polymer based on naphthalene dithiophene was designed and synthesized for the preparation of high efficiency and low energy loss non fullerene organic solar cells Among many donor building units, benzo dithiophene (BDT) is one of the most representative donor units The rigid conjugated structure and the central symmetry structure contribute to the formation of ordered molecules and the improvement of charge mobility BDT unit can be easily modified by side chain to achieve the reasonable regulation of solubility, optical band gap, molecular energy level, crystallinity and other properties Therefore, BDT is used as donor building unit in many efficient polymers Therefore, the development of BDT and its derivatives is of great significance to further improve the photoelectric performance of organic solar cells Compared with BDT, naphthalene dithiophene (NDT) has a larger conjugate plane structure, which can further improve the crystallinity of the polymer As shown in Figure 1, theoretical calculation shows that the dihedral angle between NDT unit and 2D side chain is smaller than that of BDT, which is beneficial to obtain closer molecular packing and improve carrier mobility In addition, the side chain engineering strategy used in BDT can be transplanted into the molecular design of NDT to further improve the material properties However, the research on NDT is still very limited, and there are few reports on the use of NDT based polymers in non fullerene organic solar cells Figure 1 (a) the optimized molecular structure and orbital diagram of bdts based on benzodithiophene; (b) the optimized molecular structure and orbital diagram of NDTS based on naphthalene dithiophene (source: adv funct Mater.) recently, Professor Peng Qiang's team of Sichuan University reported a new project based on The new broad band gap polymer donor pndt-st and thiophene substituted cyano indanone are the terminal small molecule receptor y6-t (as shown in Figure 2) Compared with the receptor y6, y6-t can significantly enhance the lowest unoccupied orbit (LUMO) energy level of the receptor by changing the terminal of the small molecule receptor, thus improving the open circuit voltage and photoelectric conversion efficiency of the device Due to the strong aggregation property of pndt-st, the phase separation of pndt-st: y6-t in the active layer is large, which is not conducive to exciton separation Nevertheless, 13.72% photoelectric conversion efficiency of pndt-st: y6-t device is obtained, which is slightly lower than 14.35% of pbdt-st: y6-t They then blended pbdt-st and pndt-st as donor materials with y6-t to prepare ternary blending devices By adjusting the proportion of pbdt-st and pndt-st in the donor, the phase separation of the active layer was regulated When the mass ratio of pbdt-st: pndt-st: y6-t is 0.6: 0.4: 1.2, the best phase separation is obtained while the active layer keeps high crystallinity, which promotes the exciton separation and charge transfer As a result, the photoelectric conversion efficiency of the device is significantly increased to 16.57% At this time, the energy loss of the device is as low as 0.52 EV, which is the lowest energy loss with the photoelectric conversion efficiency over 16% reported in the current literature Figure 2 (a) design idea and molecular structure of polymer donor and small molecule receptor; (b) current density voltage curve of ternary hybrid organic solar cell based on active layer pbdt-st (1-x): pndt-stx: y6-t1.2; (c) energy loss diagram of organic solar cell with photoelectric conversion efficiency over 16% reported in Literature (source: adv funct Material.) the above achievements were recently published in a dvanced functional materials (advanced Function Material 2020, 1907570) under the title of "subtitle polymer donor and molecular acceptor design enable efficient polymer solar cells with a very small energy loss" Nowadays, people and scientific research have been paid more and more attention in the economic life China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting mechanism CBG information website, chembeangoapp, chembeango official micro blog, CBG information wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the representative research groups in China, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit.