氟化PEDOT:PSS介面之偶極回復S-shaped曲線並提升有機太陽能電池耐久度之應用

Abstract

PEDOT:PSS高分子在有機太陽能電池中常用來當作電洞傳導層，具有吸水性，在工業生產製程上造成增加環境控制成本、降低良率、與增加設備維護成本。本研究中提出了一種簡單、低成本、容易施行、且可與現行製程具高度相容性之方法，預期可以大幅度降低生產過程中環境控制成本與提升產品良率及耐久度。 本研究中的有機太陽能電池以ITO基板塗佈上PEDOT:PSS成膜再利用旋轉塗佈P3HT與PCBM混合層(blend)當作吸光材料，並蒸鍍BCP當作電洞阻擋層(hloe blocking layer)和Ag當作陰極。 控制環境濕度後可以控制環境濕度對PEDOT:PSS的影響造成S-shaped曲線發生，利用含氟分子修飾改質後，成功使S-shaped曲線回復為理想的二極體曲線。進一步探討機制為在PEDOT:PSS與P3HT:PCBM介面形成理想的偶極方向，增加電洞傳導與電洞收集能力，此外，提升元件效率高達20%。 提高元件的耐久度研究上，相較於標準元件其耐久時間可延長三倍。元件封裝後經過一個月，未經氟修飾之元件，效率只剩下0.61%，而經過F2含氟分子修飾之元件效率為1.88% 。 探討效率降低的主要原因是來自Voc的大幅下降(從0.64 V降至0.45 V)，原因在於BCP緩衝層損壞所造成。In this study, we investigate the s-shape recovery and the improvement of reliability of the fluorine-modified poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) buffer layer based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blends polymer photovoltaic cells. The results of humidity-controlled experiments show that the degradation of the device performance can be recovered simply by the interfacial modification, even though the PEDOT:PSS layer has been seriously deteriorated by the air ambient. The anomalous S-shape photocurrent owing to the deterioration of the PEDOT:PSS layer can be rectified significantly as an ideal diode behavior by the surface treatments with fluorine-containing materials. Accordingly, the great enhancements of Fill factor from 30% to 62% can be achieved, where the efficiency is improved from 1.90% to 4.09%. The mechanism is due to the interfacial dipole and hydrophobicity generating by fluorine-modified PEDOT:PSS layer. Moreover, the reliability of the devices with modification shows significant increase than those without modification. The efficiency of the modified devices retains about half (1.9%) of its initial efficiency (4.1%) after 30 days compared to the unmodified one (0.6%). This phenomenon is investigated and reported for the first time. Furthermore, the overall device performance is also enhanced by ~20% as compared with the control device.