Design And Stability Research On The High Performance Organic Photovoltaics

Attribute to the innovative development of polymer donors and non-fullerene small molecule acceptors,the certified power conversion efficiency（PCE）of organic photovoltaics（OPVs）based on the bulk heterojunction（BHJ）structure has achieved a breakthrough from 10%to 18.2%in nearly ten years.In addition,the semitransparent,flexible,and large-area printable properties of OPVs make potential applications in the field of building-integrated photovoltaics and wearable electronics,etc.Although the PCE of small-area OPVs is close to 20%,the limited device stability and the sub-stable active layer phase morphology are still the key factors limiting the further development of OPVs.In this paper,we address the problems of poor interfacial stability in high-efficiency devices,unstable phase morphology of the BHJ film,and difficulty in precise regulation of the printed active layer morphology.We focus on the preparation of a stable interface layer and improving device stability.The optimization of BHJ morphology by introducing the third compound of the twisted conjugated structure,and revealing the evolution mechanism of film morphology under thermal press.Precise regulation of the vertical phase separation of the active layer in sequential printing method.Ultimately,high-efficiency and stable organic photovoltaic devices are achieved via eco-friendly printing.The specific research content includes:1.A multifunctional interfacial regulation strategy is proposed to effectively optimize the work function of Ag electrodes and the improvement of device stability.The thicker interlayer can help to reduce interfacial surface defects and keep stable surface morphology.Consequently,the device with PDINO（15 nm）/Ag as cathode records an impressive PCE of 17.48%with minimized non-radiative recombination loss of 0.239 V,the corresponding device maintains 91%of the original PCE after aging for over 60 days.Meanwhile,the PM6:e C9 device achieves a remarkable PCE of 18.22%with the enhancement of open-circuit voltage(V_OC).Furthermore,the 1cm² device based on PDINO（15 nm）/Ag shows a high PCE of 15.2%.This work highlights the promise of interfacial regulation to simultaneously stabilize and enhance the efficiency of organic photovoltaics.2.Stable non-fullerene acceptor,C11-Se,with a twisted conjugated structure is introduced as a third compound to optimize the blend film morphology and suppress the over-aggregation of the small molecule acceptor.Due to the enhancedπ–πstacking,balanced charge mobility,and uniform stable morphology,the PM6:Y6:C11-Se ternary device achieves 17.25%efficiency,which keeps nearly 90%original PCE after continuous heating over 1000 h.Moreover,the application of acceptor in PBDB-T:ITIC,J71:ITIC,and PBDB-T:PC₇₁BM systems was also verified,proving the good universality of acceptor-doping ternary strategy.3.Pseudo-planar heterojunction（P-PHJ）film with vertical gradient distribution is achieved by modulating the ordered packing crystallization of the donor film to limit the scouring effect during printing of the acceptor solution.The device based on the P-PHJ film achieves an efficiency of 17.6%,which is higher than that of the BHJ device of 16.4%.In addition,the P-PHJ with a limited D/A blend domain effectively avoids the formation of isolated phase regions caused by the diffusion of the acceptor,so the corresponding devices exhibit improved photo-,thermal-,and long-time stability.This work not only precisely constructs the gradient-distributed active layer films,but also systematically analyzes the effect in component gradient distribution in terms of device efficiency and stability.