The Microstructure Of High-efficiency Nonfullerene Polymer Solar Cells

Nowadays,the efficiency of nonfullerene polymer solar cells have rapidly increased to over 16%.Microstructure of the active layer is one of the key factors of the device performance.Study on microstructure of the active layer and the relationship between microstructure and photoelectric properties can be helpful to optimizing device processing conditions and further improving device performance.In this paper,a promising high-efficiency polymer donor PTQ10 was selected to blend with two nonfullerene acceptors(IDIC and ITIC)and a fullerene acceptor PCBM,respectively for device fabrication.The devices were optimized by thermal annealing(TA)or additives and were characterized in electrical properties and morphology.At the same time,the effects of the ratio of donor/acceptor and TA conditions on the microstructure of PM6(donor)-Y6(acceptor)films were studied.The morphology of the blend films was characterized by AFM and etching.The research results are as follows:(1)The study results on PTQ10-based devices showed that the miscibility between PTQ10 and ITIC and IDIC was much higher than that of PCBM.After TA,the phase separation size of nonfullerene films increased,and the single-component network was optimized.Additives alleviated the excessive aggregation in fullerene films,increased the crystallinity of films,optimized the single-component network.As a result,TA and additives facilitated the charge transfer in blend films,and improved fill factor and short-circuit current density of the device.(2)It can be found in the PM6-Y6 system study that the morphology of active layers changed in the vertical direction.There was a two-phase blend region with phase separation in the middle,a blocky aggregation state on the surface,while a chain aggregation state on the bottom.After TA,fiber structure and obvious single-component pathway appeared in blend films,and the molecules on the bottom surface arranged more tightly,which was obvious with the change of temperature.Films with a larger proportion of acceptor showed better thermal stability.