可拉伸高分子光电器件的研究进展

可拉伸高分子光电器件是一类基于共轭高分子的独特器件,具备在承受机械应变时仍能维持其光电性能的能力,在可穿戴电子、可拉伸显示、生物医学传感等领域展现出广阔的应用潜力.近年来,国内外学者对器件与材料设计进行了大量的探索,为其性能提升和应用拓展奠定了坚实基础.本文以外在弹性与本征弹性2个维度为切入点,深入探讨器件形态设计、材料结构调控以及薄膜组分优化等策略,总结并评述其重要成果.最后,指出未来需要关注的重点研究方向,以克服商业化过程中面临的多重挑战,并展望可拉伸高分子器件的不断进步能为有机电子领域注入新的活力.

Infrared Photodetectors and Image Arrays Made with Organic Semiconductors

Combining the strategies of introducing larger heteroatom,regio-regular backbone and extended branching position of side-chain,we developed polymer semiconductors(PPCPD)with narrow band-gap to construct the photosensing layer of thin-film photodiodes and image arrays.The spectral response of the resulting organic photodiodes spans from the near ultra-violet to short-wavelength infrared region.The performance of these short-wavelength infrared photodiodes in 900–1200 nm range achieved a level competitive with that of indium gallium arsenide-based inorganic crystalline detectors,exhibiting a specific detectivity of 5.55×1012 Jones at 1.15µm.High photodetectivity and quantum efficiency in photodiode with amorphous/nanocrystalline thin-films of 100–200 nm thickness enabled high pixel-density image arrays without pixel-level-patterning in the sensing layer.1×256 linear diode arrays with 25µm×25µm pixel pitch were achieved,enabling high pixel-density short-wavelength infrared imaging at room temperature.

The Role of Processing Solvent on Morphology Optimization for Slot-Die Printed Organic Photovoltaics

The morphology manipulation of the active layers is important for improving the performance of organic photovoltaics(OPVs).The choice of processing solvent has great impact on the crystallization and phase separation during film formation,since solvent properties,including solvent effect on molecular crystallization,boiling point,and interaction parameters,can directly change the evolution pathways associated with thermodynamics and kinetics.Therefore,revealing the underlying solvent-regulated morphology mechanism is potential to provide guiding strategies for device optimization.In this study,chloroform,chlorobenzene,and toluene are used to process PM6:Y6 blends by slot-die printing to fabricate OPV devices.The chloroform printed film forms a fibrillar network morphology with enhanced crystallization,facilitating exciton dissociation,charge transport and extraction,resulting in an optimal power conversion efficiency of 16.22%.However,the addition of the additive chloronaphthalene in chloroform solution leads to over-crystallization of Y6,and thus,increasing domain size that exceeds the exciton diffusion length,resulting in lower device efficiency.In addition,both the chlorobenzene and toluene suppress the crystallization of Y6,which drastically decreased short-circuit current and fill factor.These results demonstrate the important role of processing solvent in dictating film morphology,which critically connects with the resultant printed OPV performance.

Achieving Efficient Thick Film All-polymer Solar Cells Using a Green Solvent Additive

Adva nces in orga nic photovoltaic tech no logies have been geared toward industrial high-throughput printing manufacturing,which requires in sensitivity of photovoltaic performance reg a rd i ng to the light-harvesting layer thickness.However,the thickness of light-harvesti ng layer for all polymer solar cells(all-PSCs)is often limited to about 100 nm due to the dramatically decreased fill factor upon increasing film thickness,which hampers the light harvesting capability to in crease the power con versio n efficie ncy,and is un favorable for fabricating large-area devices.Here we dem on strate that by tuning the bulk heterojuncti on morphology using a non-halogenated solvent,cyclopentyl methyl ether,in the presence of a gree n solve nt additive of dibenzyl ether,the power con versio n efficie ncy of all-PSCs with photoactive layer thick nesses of over 500 nm reached an impressively high value of 9%.The gen eric applicability of this gree n solvent additive to boost the power conversion efficiency of thick-film devices is also validated in various bulk heterojunction active layer systems,thus representing a promising approach for the fabrication of all-PSCs toward industrial production,as well as further commercialization.

Rational Design of Conjugated Polymers for d-Limonene Processed All-polymer Solar Cells with Small Energy Loss

In this work,we designed and synthesized a novel naphthalenediimide-based n-type conjugated polymer PNDICI,which bears asymmetric backbone containing a 3-chlorothiophene unit.The asymmetric structure associated with steric effects of the chlorine atom imparts remarkable solubility to PNDICI in various organic solvents,enabling the fabrication of all-polymer solar cells(all-PSCs)by using an environmentally friendly solvent of d-limonene.Combined with a novel pyrrolo[3,4-f]benzotriazole-5,7(6H)-dione based p-type conjugated polymer P2F-Si with deep highest occupied molecular orbital energy level,the resulting d-limonene-processed all-PSCs presents an impressively high open-circuit voltage of approaching 1.0 V,corresponding to a very small energy loss of 0.49 eV.Through further morphology optimization by usingγ-valerolactone,we demonstrated an impressive device efficiency of 4.2%,which is among the best photovoltaic performance of devices processed using d-limonene and comparable to that processed by conventional solvent,suggesting the great promise of using greener solvent for fabricating high-performance all-PSCs.

Unraveling the Effect of Solvent Additive and Fullerene Component on Morphological Control in Organic Solar Cells

The manipulation of the morphology of the active layers is crucial for improving the performance of organic photovoltaic(OPV)devices. In particular, the development of non-fullerene acceptors(NFAs) has led to a large number of new materials with more complex interactions. Therefore, the investigation on the morphology control mechanism is the key aspect in providing guidance for material design and device optimization. In this study, the film morphology optimization using 1,8-diiodooctane(DIO) additive and a ternary fullerene acceptor strategy have been carried out based on the PCE10:ITIC blends. It is seen that suitable amount of DIO helps to increase the crystallization of the blended thin film. However, excessive DIO elevates the crystallization-induced phase separation and the domain size can exceed the exciton diffusion length, leading to efficiency drop. The addition of fullerene acceptor can improve the carrier transport of the blends, and its presence could retard the excessive phase separation induced by DIO additive. Under the joint optimization of the solvent additive and PCBM acceptor,the film morphology achieves a balance between crystallization and phase separation scales, the exciton diffusion and carrier transport are also optimized, and the short-circuit current(JSC) and fill factor(FF) of the device can be improved significantly.