| With the growing popularity of flexible wearable electronics,the public demand for wearable energy devices is gradually increasing.Due to the limitations of traditional batteries such as lack of flexibility,non-stretchable and difficult to weave,the development of flexible energy devices has gained widespread attention.For the flexible wearable electronics,flexible energy batteries do not only serve the role of energy supply,but to some extent also determine the design and function of wearable electronics.Currently,certified flexible perovskite solar cells（F-PSCs）have a power conversion efficiency of 22.9%,making them an important energy supply option for wearable electronics.For F-PSCs,it is crucial to develop a transparent conducting electrode（TCE）.In this paper,polyurethane（PU）nanofibers were prepared by electrostatic spinning technique,and post-treatment methods such as magnetron sputtering technique and substrate transfer were combined to obtain PU/Ag composite nanofiber transparent electrodes.Different performance of transparent electrodes were obtained by controlling the spinning time,and then the performance was optimized according to some corrosion and aging problems in transparent electrodes and perovskite,and the performance improvement were compared through the fabrication of F-PSCs,which are divided into three parts as follows:（1）The flexible transparent electrode was prepared by electrospinning method combined with post-treatment.Firstly,PU nanofibers with excellent performance were obtained by exploring the electrospinning parameters,such as spinning solution concentration and so on,and PU/Ag composite nanofiber transparent electrodes with good light transmission,high conductivity and flexibility were obtained by combining magnetron sputtering technique and transfer of fiber electrode to the substrate.The results show that the optical transmittance of the transparent electrode（including the substrate）can reach more than 80%when the spinning time is 5 min,and the conductivity is 2.31×107 S m-1,which has the same order of magnitude as the metal Ag;in terms of mechanical properties,it had more than 30%elongation at break and the breaking strength was as high as about 40 MPa,and the effect on light transmittance during the stretching process The effect on light transmittance during stretching is minimal（light transmittance is still above 80%）,and the resistance of the electrode is found to rise only about 13.5%after 100 bending cycles（bending radius of 2 mm）.The prepared transparent electrodes were applied to perovskite solar cells,and the rigid and flexible device efficiencies of14.43%and 7.92%were obtained,respectively.Placing the unencapsulated rigid and flexible cell devices in an environment with a relative humidity of 30%±5%and a temperature of 25°C±5°C to test the environmental stability revealed that the efficiency of the rigid cell could maintain 82.7%of the initial efficiency and the flexible cell could maintain 78.6%of the initial efficiency after 10 days.When the bending stability test was performed on the flexible battery device with a bending radius of 2 mm,the efficiency of the flexible device dropped to 80%of the initial efficiency after 320 consecutive bending cycles.（2）To address the problem that the halogen elements of perovskite in the battery devices tend to combine with metals and thus reduce the efficiency and stability of the devices,a benzotriazole（BTA）inhibitor was selected to form an N-Ag-N chemical coordination with Ag,which can form an ultra-thin barrier film between the layers and thus prevent the binding of Ag and halogen ions.The results show that the unencapsulated cell device can maintain more than 80%humidity stability of the initial efficiency after 7days in humid air（relative humidity 40～60%）（rigid battery 83.6%,flexible battery81.5%）,and can also maintain more than 80%thermal stability in a vacuum oven at 85°C（rigid battery 82.2%,flexible battery 80.1%）.In the 10-day environmental stability test（relative humidity 30%±5%,temperature 25°C±5°C）,the rigid battery with BTA can maintain 85.7%of the initial efficiency,and the flexible battery can maintain 84.0%of the initial efficiency.（3）Aiming at the problem that perovskite is easily damaged by ultraviolet light,an ultraviolet light absorber（UV-370）and a down-conversion luminescent material（fluorescent blue dye）were selected as optical functional layers to absorb ultraviolet light or convert ultraviolet light into visible light and be absorbed by the perovskite layer,thereby improving the energy conversion efficiency and optical stability of the battery device.In the rigid devices,the efficiency was increased from 14.43%to 15.85%with UV-370 and 16.27%with fluorescent blue dye,while in the flexible devices,the efficiency was increased from 7.92%to 9.86%with UV-370 and only 8.06%with fluorescent dye.The water contact angle of the transparent electrode was first characterized before testing the humidity stability of the device,and it was found that the size of the water contact angle increased from the original 66.5°to 73.4°with UV-370and to 93.5°with the addition of fluorescent blue dye,especially for the fluorescent blue dye,the hydrophobic performance was better than that of UV-370.After 10 days of humidity stability（40～60%relative humidity）test,the control group of both rigid and flexible cell devices dropped to about 30%of the initial efficiency,while the PSCs with both materials added were able to maintain more than 80%of the initial efficiency,a performance that coincided with the water contact angle test results,indicating that the hydrophobic properties of both materials positively influenced the humidity stability of the PSCs devices.To further verify the UV stability of the devices,the unencapsulated perovskite solar cells were subjected to 10 days of continuous light irradiation tests,and the results show that the efficiency of the device with fluorescent blue dye is higher than that of the device with UV-370.The stability of the rigid battery with fluorescent blue fuel on the 10th day is increased from 82.7%to 87.5%compared with the device without fluorescent blue dye,and the flexible battery is increased from 78.6%to 86.5%. |
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