Low-temperature dynamic vacuum annealing of ZnO thin film for improved inverted polymer solar cells

The effect of low-temperature dynamic vacuum annealing (DVA) of sol–gel ZnO films on inverted polymer solar cells (IPSCs), which are composed of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PC61BM), was systematically investigated. The results show that IPSCs with low-temperature DVA-based ZnO films exhibit 15.9% enhancement within a power-conversion efficiency (PCE) of 4.01%, compared with IPSCs with conventional annealing-process-based ZnO films. The surface morphology measurement of ZnO films, light intensity dependent solar cell behaviors, and impedance spectroscopy of devices were investigated to study the performance of IPSCs. The dramatic enhancement of PCE was attributed to the improved surface morphology, optimized carrier transport characteristics, prolonged charge carrier lifetime, and reduced recombination rate. These results indicate that the low-temperature DVA process could be a promising method for producing high-quality ZnO films and high-performance IPSCs.