Efficient Light Harvesting in Thick Perovskite Solar Cells Processed on Industry-Applicable Random Pyramidal Textures

Abstract

Light management is key to high-performance solar cells, particularly to monolithic perovskite/Si tandem solar cells and in real field applications. Random pyramidal textures of commercial Si solar cells (height ∼2–5 μm) allow for efficient light harvesting; however, solution processing of conventional perovskite thin films (thickness ∼0.5 μm) over these large textures exhibits bad coverage, resulting in shunting paths. In response to this challenge, we present high-efficiency perovskite solar cells (PSCs) processed on replicated industry-applicable random pyramidal textures with a smaller pyramid size of ∼1–2 μm. As a first step, we develop planar PSCs with close to micrometer thick perovskite absorber layers that maintain efficient charge carrier extraction by using a Lewis base additive and exhibit a power conversion efficiency of up to 18%. Employing these thick films in textured PSCs with inverted pyramids improves the light management as compared to the planar reference, with the AM 1.5G weighted reflectance being reduced from 9.9 to 5.2%. The reduced broadband reflectance in conjunction with enhanced light trapping increases the current generation by 7.7% relative, which corresponds to 87.3% of the maximum attainable short-circuit current density. In addition, we maintain a high fill factor and open-circuit voltage comparable to that of the planar reference PSC despite the increased surface area of the texture. Thereby, our champion textured PSC exhibits a stabilized power output of 18.7% at maximum power point tracking for 5 min. Finally, the textured PSCs also exhibit improved current generation for all angles of incidence, emphasizing their advantages at realistic irradiation conditions and for bifacial applications.

Four‐Terminal Perovskite/Copper Indium Gallium Selenide Tandem Solar Cells: Unveiling the Path to >27% in Power Conversion Efficiency

“…Various studies have already demonstrated the feasibility of such high thicknesses in perovskite absorbers while maintaining high charge carrier mobility. [24,[51][52][53] Finally, replacing the front MgF 2 antireflection coating with micro-textures will improve the PCE by 0.73% (see Figure 4c). Micro-textures increase the probability of light in-coupling by allowing multiple reflections at the textured surface and increase the optical pth length through the absorber.…”

Mitigation of Open‐Circuit Voltage Losses in Perovskite Solar Cells Processed over Micrometer‐Sized‐Textured Si Substrates

“…The substrates were heated up to 300 °C for 75 min in the vacuum chamber before deposition and this temperature was maintained during the whole deposition process, the deposition parameters can be found in ref. [80] The average sheet resistance of the ITO films was ≈14 Ω cm −2 .…”

“…[90,102] We find that the 1.6 m perovskite precursor solution (which is essential to provide full surface coverage over the micrometer-sized pyramidal textures as discussed in the next section) results in a high volume fraction of PbI 2 when processed over a planar Si substrates employing 10% excess PbI 2 (see XRD spectra in Figure 3a). [80,112] Interestingly, the PbI 2 diffraction peak intensity is strongly decreased once the perovskite thin film is processed over the textured surface compared to the planar reference. We emphasize that we used the same perovskite precursor solution and the same processing parameters for both the textured and planar Si substrates.…”

“…Such a decrease in crystalline PbI 2 volume fraction has been reported before, for example for recipes using additives in the perovskite precursor solution if they tend to form complex compounds with the PbI 2 (e.g., Lewis acids and bases). [80,[113][114][115] However, this explanation is not plausible in case only the substrate type is varied (from planar to texture). A more plausible explanation for the reduced PbI 2 volume fraction is the interaction of the perovskite with the NiO x -based HTL.…”

“…We note that such voids are absent if the perovskite is processed over a planar surface using early quenching as reported in our previous work. [80] To resolve this issue and minimize the trapped DMSO volume in the pyramids valleys, we optimized the anti-solvent dropping time to 55 s, which we term "late quenching" in the following. As shown in the SEM cross-sections in Figure 2b and Figure S1b (Supporting Information), the pyramids valleys are completely filled with no voids being present.…”