Fabrication And Performance Of Flexible Organic Solar Cells

Compared to the traditional inorganic solar cells, organic polymer cell has the advantages of low-cost, good mechanical flexibility and lightweight. At present, some critical problems must be solved in the power conversion efficiency (PCE) and the stability of organic polymer cell. The fabrication of the device with a flexible substrate instead of rigid substrate brings many new problems. While without annealing treatment, the morphology of the active layer deposited can not meet the requirements of effective separation of the carriers. Annealing treatment, solvent treatment and post-annealing treatment are very easy to implement on the rigid substrate to improve the performance of device which is not applicable for a flexible device. In this paper, we try to improve the aspects in the fabrication of flexible device through the work as follows:The device performances of organic solar cells based on regioregular poly (3-hexylthiophene)(P3HT) and phenyl C61-butyric acid methyl ester (PCBM) blends casting from1,2,4-trichlorobenzene (124-TCB) and o-dichlorohenzene (ODCB) were fabricated. The influence of the type of solvent and the different proportions of additives on the performance and stability of the photovoltaic device were investigated. For the device using ODCB as solvent, device performances with Voc of0.52V, Jsc of10.8mA/cm2, FF of35.4%, and PCE of1.99%are obtained. For the device with124-TCB as solvent shows enhanced performance with Voc of0.53V, Jsc of7.02mA/cm2, FF of56.7%, and PCE of2.11%. The device with1,3,5-trichlorobenzene (135-TCB) as additive shows enhanced performance with Voc of0.60V, Jsc of9.07mA/cm2, FF of55.7%, and PCE of3.03%, respectively. The stability of the device is also improved, which can be seen from the heat aging decay curve.The effect of ultraviolet (UV) irradiation treatment with different irradiation intensity and treatment time of poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate)(PEDOT:PSS) film on the performance and stability of polymer solar cells based on regioregular poly (3-hexylthiophene)(P3HT) and methanofullerene-phenyl C61-butyric acid methyl ester (PCBM) blend was investigated. Ultraviolet-visible (UV-vis) transmission spectrum X-ray photoelectron spectroscopy (XPS) contact angle measurement atomic force microscopy (AFM) and Kelvin Probe method were conducted to characterize the UV-treated PEDOT:PSS film. The results demonstrate that UV treatment could improve the PCE and stability of PSCs effectively. The best performance is achieved under1200uW/cm2UV treatment for50min. Compared to the control device,the optimized device exhibits enhanced performance with Voc of0.59V, Jsc of12.3mA/cm2, FF of51%, and PCE of3.64%, increased by3.5%,33%,8.7%and50%, respectively. The stability of PSCs enhanced2.5times just through UV treatment on the PEDOT:PSS buffer layer. The improvement of device performance and stability is attributed to be originated from the improvement of wettability property, the increasing in work function (WF) of the PEDOT:PSS film by UV treatment and the removal of the PSS during the UV treatment.The removal of the insulator PSS from PEDOT:PSS surface will not only increase the conductivity of the film but also improve its morphology and long term stability. While the impact of UV treatment on the transparence of PEDOT:PSS film is negligible. The strategy of UV treatment to improve the device performance and stability is attractive due to its simplicity, cost-effective and is well suitable for large scale commercialization production.