Enhancing efficiency and stability of organic solar cells through a simplified four-step synthesis of fully non-fused ring electron acceptor

Design and synthesis of superior cost-effective non-fullerene acceptors(NFAs)are still big challenges for facilitating the commercialization of organic solar cells(OSCs),yet to be realized.Herein,two medium bandgap fully non-fused ring electron acceptors(NFREAs,medium bandgap,i,e.,1,3-1,8 eV),namely PTR-2Cl and PTR-4Cl are synthesized with only four steps by using intramolecular noncovalent interaction central core,structured alkyl side chain orientation linking units and flanking with different electron-withdrawing end group.Among them,PTR-4C1 exhibits increased average electrostatic potential(ESP)difference with polymer donor,enhanced crystallinity and compactπ-πstacking compared with the control molecule PTR-2CI.As a result,the PTR-4Cl-based OSC achieved an impressive power conversion efficiency(PCE)of 14.72%,with a much higher open-circuit voltage(V_(OC))of 0.953 V and significantly improved fill factor(FF)of 0.758,demonstrating one of the best acceptor material in the top-performing fully NFREA-based OSCs with both high PCE and V_(OC).Notably,PTR-4Cl-based cells maintain a good T_80lifetime of its initial PCE after over 936 h under a continuous thermal annealing treatment and over1300 h T_(80)lifetime without encapsulation.This work provides a cost-effective design strategy for NFREAs on obtaining high V_(OC),efficient exciton dissociation,and ordered molecular packing and thus high-efficiency and stable OSCs.

Recent Progress in All-Solution-Processed Organic Solar Cells

All-solution-processed organic solar cells(OSCs)(from the bottom electrode to the top electrode)are highly attractive thanks to their low cost,lightweight and high-throughput production.However,achieving highly efficient all-solution-processed OSCs remains a significant challenge.One of the key issues is the lack of high-quality solution-processed electrode systems that can replace indium tin oxide(ITO)and vacuum-deposited metal electrodes.In this paper,we comprehensively review recent advances in all-solution-processed osCs,and classified the devices as the top electrode materials,including silver nanowires(AgNWs),conducting polymers and composite conducting materials.The correlation between electrode materials,properties of electrodes,and device performance in all-solution-processed OSCs is elucidated.In addition,the critical roles of the active layer and interface layer are also discussed.Finally,the prospects and challenges of all-solution-processed OSCs are presented.

Enhanced Performance via π-Bridge Alteration of Porphyrin-Based Donors for All-Small-Molecule Organic Solar Cells

All-small-molecule organic solar cells (ASM OSCs) are promising for commercial application due to the well-defined chemical structures, convenient purifying process and low batch-to-batch variation. However, the similarity of molecule structures between small molecule donors and acceptors makes a hard regulation of their blend morphology, which will limit the efficiency.

Silane or Siloxane-Side-Chain Engineering of Photovoltaic Materials for Organic Solar Cells

With the tactful material design,skillful device engineering,and in-depth understanding of morphology optimization,organic solar cells (OSCs) have achieved considerable success.Therefore,OSCs have reached high power conversion efficiencies (PCEs) exceeding 19%.Especially,continuously emerging new materials have been considered as one of the key factors to improve the PCEs of OSCs.Among molecular design strategies,side-chain engineering is an easy and commonly-used means which can optimize the solubility,alter intermolecular stacking arrangement,fine-tune the open circuit voltage (VOC),thus ultimately improve the performance.As hybrid side chains,silane and siloxane side chains have considerable effects,not only in increasing the carrier mobility and tuning the energy level,but also in affecting the crystallinity and molecular orientation.In this review,the latest developments in photovoltaic materials based on silane and siloxane side chains are presented to illustrate the structure-property relationships.The review comprehensively includes silane-side based polymer/small molecule donors;siloxane-side based polymer/small molecule donors,and polymer/small molecule acceptors.Then the similarities and differences between these two side chains are demonstrated.Finally,the possible applications and future prospects of silane and siloxane side chains are presented.

氧化石墨炔提升界面电荷传输及分离以构筑高效二元有机太阳能电池器件

通过界面工程调节载流子动力学是提高太阳能电池器件效率的关键方式.在本工作中,我们成功制备了具有大量官能团的高分散性氧化石墨炔(GDYO),并将其应用于优化空穴传输材料PEDOT:PSS的性质以制备有机太阳能电池器件.结果表明,GDYO与PEDOT:PSS之间的π–π相互作用有利于优化电荷转移通道,提高空穴传输层的电导率和载流子迁移率.此外,界面接触的改善有助于抑制电荷的复合,提高空穴传输层和活性层之间的电荷提取.同时,活性层的形貌得到有效改善,瞬态吸收测试结果证实这有利于载流子分离率的提升,进而提高器件性能.因此,通过对载流子动力学的系统性优化,二元有机太阳能电池的光电转换效率达到17.5%,认证效率达到17.2%.本工作结果表明功能化石墨炔在有机光电器件领域具有广阔的应用前景.

Recent progress on all-small molecule organic solar cells using small-molecule nonfullerene acceptors

Recently,solution-processed organic solar cells combining small-molecule donor and nonfullerene acceptor have achieved breakthrough results with the certified efficiency over 15%.These impressive progresses are driven by the concerted efforts of modifying the donor and acceptor materials and optimizing the morphology.Considering the defined chemical structures and easily tuned properties of small-molecule materials,it is of great necessity and importance to pay more attentions on the topic of all-small molecule organic solar cells.Here,we summarize the recent progress of all-small molecule organic solar cells from the prospect of materials'evolutions and expect to provide some hints for its future developments.The involved small-molecule donors including oligothiophene-,benzodithiophene-,naphthodithiophene-,and porphyrin-based materials are discussed to illustrate the relationship of chemical structures,properties,and device performance.Then,the small-molecule nonfullerene acceptors in all-small molecules organic solar cells are discussed to highlight their vital role.Finally,we will present the challenges and future of this research area.

Recent Progress in Design of Organic Electro-optic Materials with Ultrahigh Electro-optic Activities

Rationally designed organic electro-optic (OEO) materials demonstrate ultra-large electro-optic (EO) activities, affording inorganic-organic hybrid photonic devices with low drive voltage, large bandwidth, low energy consumption, and small footprint. OEO materials hold the potential to achieve EO coefficients (r_(33)) over 1000 pm/V. Over the past decade, however, the best performance of OEO materials is limited to 300—600 pm·V^(−1). This is partly because of the concern of increasing dipole moment and optical loss due to the redshifted absorbance of high hyperpolarizability chromophores. Recent advance of theory-guided design enables the OEO materials to achieve greatly enhanced hyperpolarizability and EO activity with dipole moment and propagation loss within acceptable constraints. Simultaneously, progress in hybrid device designs has greatly shortened the length of modulating waveguide, which resulted in significantly reduced sensitivity to propagation loss from redshifted absorption of OEO materials. Driven by theory-guided design method, several high-performance OEO materials have been presented with greatly enhanced EO coefficients beyond 1000 pm·V^(−1). This brief review summarizes the strategies to improve the EO activity including molecular engineering and hyperpolarizability, highlights the recent great progress in design of high-performance OEO materials, and discusses the problems needed to be solved in application for current OEO materials.

A-π-D-π-A Type Small Molecules Using Ethynylene Linkages for Organic Solar Cells with High Open-circuit Voltages

Introducing ethynylene linkages in a conjugated molecule can deepen the HOMO level, decrease the steric con- straints and better delocalize the n electrons and so on, which are beneficial for organic solar cells. Furthermore, the typical method of introducing acetylene linkages by Sonogashira reactions can avoid the usage of toxic stannyl in- termediates and potentially dangerous lithiation reactions. In this study, two simple small molecules BEDPP and NEDPP are designed and synthesized, in which two diketopyrrolopyrrole units are symmetrically connected to benzene and naphthalene cores, respectively, via acetylene linkages. And the BHJ （Bulk Heterojunction） solar cells based on BEDPP and NEDPP without using solvent additive and without any post-treatment for the active layers provide us power conversion efficieneies of 1.48% and 2.31% with remarkably high open circuit voltages up to 0.90 and 0.98 V, respectively.

Single-junction organic solar cell smashes performance record

Organic solar cells(OSCs)have become a major focus in the field of the third-generation renewable energy thanks to their outstanding advantages of low cost,light weight and flexibility.In recent years,efforts dedicated to OSCs via material design,morphology optimization,and mechanism analysis have made remarkable progress,with power conversion efficiency(PCE)exceeding 19%.However,compared with inorganic solar cells(e.g.,Si or perovskite),the performance of OSCs remains limited by non-ideal exciton and charge transport.