Light absorption enhancement in perovskite solar cells using microstructured polymers imprinted by roll-to-roll hot embossingThursday (25.06.2020) 16:20 - 16:40 Room 3
In the last decade, perovskite solar cells (PSC) have attracted the attention of the photovoltaics community due to their rapid increase in efficiency up to an impressive 23%. This photovoltaic technology offers additional remarkable features, such as low weight, potential low manufacturing cost, and the possibility to fabricate these devices onto flexible substrates, which opens the opportunity to integrate the whole manufacturing process in large area roll-to-roll production lines . Among the many possible routes to further improve the device efficiency, enhancing the absorption of sunlight by using textured substrates appears to be a simple and scalable solution. With a suitable designed microstructured substrate, incoming light can be scattered or diffracted by the microtextures elongating its optical path inside the semiconductor and therefore increasing the probability of absorption. In this work, two manufacturing methods are combined to pattern a transparent polymeric substrate with enhanced light trapping capabilities. Namely, a cylindrical metallic mold is firstly structured by Direct Laser Interference Patterning (DLIP) and then it is used in a roll-to-roll (R2R) hot embossing unit to transfer the microtexture to a polymeric foil (Figure 1b) at a throughput of 1 m2/min. The SEM image in Figure 1a corresponds to a patterned polyethylene terephthalate (PET) foil with periodic grooves with a spatial period of 2.7 µm combined with low and high spatial frequency laser induced periodic surface structures (LIPSS). Then, these foils were used as flexible substrates for PSC (Figure 1c and d) resulting in an increase in the efficiency of 18% for the best devices. The optical characterization by global transmittance/reflectance and diffraction efficiency measurements suggest that the increase in efficiency is attributed to an enhancement in the absorption in the perovskite layer due to diffraction of the incoming light by the patterned substrate.
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