Polymer Photovoltaic Performance and Degradation on Spray and Spin Coated Electron Transport Layer and Active Layer

Inverted polymer photovoltaic performance and degradation of a spray coated ZnO electron transport layer and active layer were studied in comparison with corresponding spin coated devices. The spray coated ZnO layer with a spin coated P3HT:PCBM active layer exhibited a higher efficiency (3.76%) than the device (3.11%) with the spin coated ZnO and active layer due to the increase in fill factor from 42.38% to 63.14%. This was a resultant of the tighter grain packing and lower root mean squared roughness in the spray coated ZnO film. The spray coated P3HT:PCBM layer with a spin coated ZnO layer also led to a higher efficiency (3.19%) than that (2.72%) of the spin coated P3HT:PCBM film. This increase in efficiency is due to a higher phase separation with more fibril structures in the active layer from spray coating. In addition, a degradation measurement was performed on both the spray and spin coated P3HT:PCBM layers. The spray coated P3HT:PCBM devices degraded much faster than the spin coated cells, which was possibly caused by oxygen trapping in the devices as the spray coating was performed in air, while the spin coating was conducted in the inert nitrogen environment. The spray coating was performed by a simple airbrush that can potentially be modified for large scale manufacturing of polymer solar cells at a much lower cost than other techniques.