Stability of Non-Flexible vs. Flexible Inverted Bulk-Heterojunction Organic Solar Cells with ZnO as Electron Transport Layer Prepared by a Sol-Gel Spin Coating Method

Abstract

In this research, inverted bulk heterojunction organic solar cells (BHJ OSC) with poly(3-hexylthiophene-2,5-diyl): (6,6)-phenyl C61 butyric acid methyl (P3HT:PCBM) as the active layer were fabricated by a sol-gel spin coating method using flexible PET and non-flexible glass as substrates. The power conversion efficiency (PCE) and the stability of the cells were investigated. According to the results, the non-flexible device showed higher short circuit current (Jsc) as well as open-circuit voltage (Voc) as compared to the flexible one so that 2.52% and 0.67% PCE for non-flexible and flexible cells were obtained, respectively. From the stability point of view, the non-flexible device maintained 51% of its initial efficiency after six weeks in a dark atmosphere, while it was about 19% for the flexible cell after four weeks. The most important reason for the higher PCE with the higher stability in the non-flexible cell can be attributed to its higher shunt resistance (Rsh) and better interlayer connections at the electron collector side.