par Godefroid, Blaise ;Kozyreff, Gregory
Référence International Conference on Hybrid and Organic Photovoltaics (HOPV18) (2018 May 28th - 31st: Benidorm, Spain)
Publication Non publié, 2018-05-29
Poster de conférence
Résumé : In a recent paper, the concept of a Two-Resonance Tapping Cavity (TRTC) was demonstrated as a general, purely photonic, way to increase the EQE of organic cells. The idea is to put a dielectric layer between the capping layer and an ultra-thin top electrode. This provides a new broad resonance in the absorptivity of the cavity in addition to the resonance between the two electrodes. By judiciously locating this second resonance relative to the spectral response of the active molecules, a significant boost of short circuit current has been demonstrated [1].Progressing from this success, we study a modification of the TRTC, which we call TRTC-tandem, where an Ultra-Thin Metal Film (UTMF) separates the active region into two, resulting in a three-terminal parallel tandem cell comparable to the one discussed in [2], while doing so, we keep a single active material in the cell. The hope is to add a further resonance at long wavelengths in order to increase the light intensity, and hence the EQE, where the absorption coefficient drops. Using the same materials as those studied in [1] we find that the sort-circuit current can be improved from the best configuration of [1] by nearly 2 mA/cm². Moreover, we observe that the optimal outcome is obtained with a relatively thick Ag layer (~20 nm) as central UTMF, which guarantees a good conduction of the common electrode. These results are confirmed for several active materials: PTB7-Th:PC71BM, P3HT:PC61BM and perovskite.Furthermore, we demonstrate the generality of our approach by applying it to a general class of molecular absorption spectra, that sharply decay for wavelengths larger than a maximum value. Thanks to the central UTMF, photons in the long-wavelength, low-absorption part, can be significantly better harvested.Finally, we compare the cell performance when the front electrode is ITO and when it is UTMF. Depending on the transporting layer materials, one or the other of the two options yields the best performance but only marginally so. Hence, the TRTC-tandem configuration seems to be a good candidate to improve the organic solar and/or to get out of the indium dependency.AcknowledgementWe thank Jordi Martorell (ICFO, The Institute of Photonic Sciences) for helpful discussions and for communicating their data.References:[1] Quan Liu et al. Advanced Energy Materials, 7(18):1700356-n/a, 2017. 1700356.[2] Lijian Zuo et al. Advanced Materials, 26(39):6778-6784, 2014.