Abstract
We demonstrate the feasibility of fabricating tandem polymer solar cell based on the identical blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl- C61butyric acid methyl ester (PCBM) as active layers for both cells with various kinds of interlayer structures. Furthermore, we also investigate the effect of active layer thickness on the performance of the tandem polymer solar cell. We repeat the procedure for preparation of the tandem cell with Al/MoO3 as interlayer reported in the literature and also vary the process condition, the thickness of interlayer, the annealing time, or add PEO into interlayer. However these interlayers can’t effectively protect the prior-deposited active layer from dissolving in the spin coating of another active layer due to their loose structures. The reported performance of tandem polymer solar cell with Al/MoO3 as the interlayer may be just taken from small portion of large amount of samples. When we use Ag as one of the interlayer component, which is robust enough to protect the underlying polymer film from deterioration by the solvent or solution infusion. With Al/Ag/PEDOT:PSS as the interlayer, the stacking cell Voc remarkably rises up. Furthermore, by using Al/Ag as the electrode, and the same interlayer structure, the s-shaped current-voltage curve can be avoided and the Voc further promotes up to 1.23 V, which is almost the exact summation of the Voc of the single cells. We measure the transmission spectra of the upper cell with the interlayer to estimate the light intensity that emits the bottom cell, by which the active layer thickness is adjusted to improve device performance. Compared to the reported interlayers, Al/MoO3, MoO3/Ag/Al/Ca, ZnO/GO/PEDOT, the tandem cell with Al/Ag/PEDOT:PSS as interlayer give the highest Voc of 1.23 V.