Perovskite solar cells are driven a paradigm shift in photovoltaics (PV) since they are breaking with the existing tradeoff between efficiency and fabrication cost.1,2 A little over two years this solar cell technology is at the top of the emerging PV efficiency race, reaching certified values that surpass all the ones attained in cells based on solution-processed materials. Herein we provide a full description of the optical behavior of perovskite solar cell devices. We performed an in-depth experimental and theoretical analysis of the optical effects occurring in state-of-the-art solution-processed perovskite cells, i.e. organic-inorganic metal halide perovskite, prepared using a one-step deposition method, sandwiched between an n-type and p-type charge collection layer. We developed a theoretical model using a method based on the transfer matrix formalism,3 which allows us to calculate the electric field intensity within the layered structure and thus to visualize the effect of each layer comprising the cell on the spatial distribution of the radiation in the PV device. To check the suitability of the proposed theoretical model, we fitted the experimental reflectance, transmittance and absorptance spectra of devices measured at normal incidence. The layout of the device determines the field intensity distribution along the cell and hence the spatial and spectral distribution of optical absorption in the device. This allows us to estimate the amount of light that is captured by each absorbing layer in the perovskite cell, and hence to discriminate between productive (absorbed in the perovskite material) and parasitic (absorbed in other components such as FTO, or the metallic contact) absorption. Our work also provides a theoretical framework in which the optical response of solar cells integrating photonic enhancing components can be rationalized. Also, as demonstrated in other PV technologies, photonic designs may lead to resonant photocurrent generation4 to improve the efficiency of the device. References: 1. Lee, M.M., Teuscher, J., Miyasaka, T., Murakami, T. N., & Snaith, H. J. Science 338, 643-647 (2012). 2. Liu, M., Johnston, M. B. & Snaith, H. J. Nature 501, 395-398 (2013). 3. Lozano, G., Colodrero, S., Caulier, O., Calvo, M. E., & Mï¿½guez, H. J. Phys. Chem. C 114, 3681-3687 (2010). 4. Anaya, M., Calvo, M. E., Luque-Raigï¿½n, J. M. & Mï¿½guez. J. Am. Chem. Soc. 135, 7803-7806 (2013).
Institute of Materials Science of Seville (CSIC-US)
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