Light coupling to quasi-guided modes in nanoimprinted perovskite solar cells
Introduction
Within only a few years of research, perovskite photovoltaics (PV) emerged as a promising technology for highly efficient and low-cost solar cells, demonstrating high power conversion efficiencies (PCE) exceeding 24% on a laboratory scale [1]. Organic-inorganic perovskite materials combine excellent optoelectronic properties, such as high absorption coefficients and high carrier mobilities, with low material costs and a wide range of potential deposition techniques [2]. Moreover, via compositional engineering of the halide anion in the crystal structure, their bandgap can be easily tuned, making this material a prime candidate for multi-junction PV [[3], [4], [5], [6]]. Thereby, for the first time, a versatile and inexpensive thin-film technology for multi-junction PV is at hand that promises to exceed the Shockley-Queisser limit of the market-dominating single-junction crystalline silicon solar cells [7,8].
The recent advances in perovskite solar cells have been largely underpinned by advances in the composition [[9], [10], [11]] and morphology [12] of the perovskite absorber layer as well as progress in device architectures [13], which employ custom passivation [14,15], hole- and electron-transport layers [[16], [17], [18]]. Furthermore, extensive research has been directed to advance the light harvesting by light-incoupling concepts like random pyramids [19], micro lens arrays [20], nanophotonic front electrodes [21], and fiber array-based front electrodes [22]. Moreover, improved light trapping has been demonstrated via nano- and micro-patterned charge transport layers [[23], [24], [25], [26], [27], [28], [29]], nanophotonic back electrodes [30], rough back electrodes [31], and corrugated substrates for single [32] and multi-junction [33,34] perovskite PV. In addition, nano-patterning the perovskite layer with periodic textures was proposed [[34], [35], [36], [37], [38], [39]] and simulations have predicted an improved short-circuit current density (JSC) in such nanophotonic perovskite solar cells [40,41]. In our recent study, we have shown that patterning the perovskite absorber layer enhances the absorption by coupling incident sunlight to quasi-guided modes [40]. Enhancing the absorption in the weakly absorbing regimes close to the bandgap of the perovskite is essential to maximize the PCE of both opaque as well as of semi-transparent perovskite solar cells [42]. Various nano-patterning techniques have been proposed for the perovskite layer: (1) focused ion beam lithography [43,44], (2) electron beam etching [45,46], recrystallization through phase transformation [47], and (3) thermal nanoimprint lithography (TNIL) [37,38,[48], [49], [50], [51]]. From these, TNIL appears particularly promising as it allows for the patterning of nanostructures at both large scale and high throughput, which is crucial for upscalable fabrication technologies such as roll-to-roll processing [52,53]. In the case of perovskite PV, the applied heat and pressure during the TNIL process is reported to trigger the recrystallization of the perovskite absorber. As shown in the work Mayer et al., the grains of the multicrystalline perovskite thin-film increase during an imprint step [50]. Using a textured mold to directly pattern the perovskite solid-state film with well-designed periodic nanostructures improves its absorption properties and can yield a better crystal structure that exhibits fewer surface defects [49].
The interest in nano-patterned perovskite layers is broad within optoelectronics, having been employed to demonstrate optically-pumped lasing [37,44,49], light-emitting diodes [47] and nanostructured photodetectors [48]. Moreover, recent studies reported an improved JSC for nanoimprinted perovskite solar cells along with a broadband enhancement of the external quantum efficiency [51,54]. Whereas Kim et al. identified the uniaxial compression leading to an enhanced crystal quality and Wang et al. described the nanophotonic light trapping by diffraction of incident light at the textured perovskite interface. However, the enhanced absorption via the coupling of incident light to distinct quasi-guided modes was not examined in detail. The present work builds up on these studies and provides a detailed optical analysis of light coupling to quasi-guided modes in the nanoimprinted perovskite solar cells. An enhanced JSC of the nanoimprinted perovskite solar cells by 2% relative with respect to their planar references is demonstrated. The improvement in PCE is a result of the enhanced external quantum efficiency close to the bandgap of the nanoimprinted perovskite solar cells. Moreover, this study experimentally and numerically discusses the limited enhancement in opaque perovskite solar cells by a nanophotonic absorber layer and reveals the potential of nanophotonic semi-transparent perovskite PV for multi-junction solar cells by a relative enhancement in JSC of 9% compared to their planar references.
Section snippets
Methods
Device fabrication: Pre-patterned indium tin oxide (ITO) substrates on glass (Luminescence Technology) were cleaned in ultrasonic baths of detergent, deionized water, acetone and isopropyl alcohol for 10 min each. Then the tin oxide (SnO2) electron transport layer was spin-coated at a speed of 4000 rpm for 30 s. Therefore, a 15% aqueous colloidal dispersion of SnO2 (Alfa Aesar) is diluted to a final concentration of 2%. The spin-coated SnO2 layer was then annealed in air at 250 °C for 30 min.
Nanoimprinted perovskite solar cells
In order to enhance the JSC in perovskite solar cells, the perovskite layer is periodically textured by TNIL. The textured perovskite enhances the absorption by coupling incident light to quasi-guided modes. The TNIL is performed directly on the triple cation perovskite (Cs0.1(MA0.17FA0.83)0.9Pb(I0.83Br0.17)3) layer, which is solution deposited on the glass /indium tin oxide (ITO) /tin oxide (SnO2–np) superstrate. Prior to the TNIL, the triple cation perovskite layer is annealed at 100 °C for
Conclusion
This work presents a facile route to fabricate nanophotonic perovskite solar cells and demonstrate a 2% improved power conversion efficiency of nanoimprinted perovskite solar cells with respect to their planar references. The enhanced absorption by coupling incident light to quasi-guided modes in the perovskite absorber layer is achieved by texturing the perovskite layer using thermal nanoimprint lithography. The enhanced absorption increases the short-circuit current density of the
Competing financial interest
The authors declare no competing financial interest.
Acknowledgements
The authors would like to thank S. Moghadamzadeh and S. Geisert for conducting the XRD measurements, M. Worgull and M. Schneider for providing the nanoimprint infrastructure, L. Hahn and A. Bacher for conducting the electron-beam lithography, and M. Guttmann for support during the fabrication of the molds. Further, the authors would like to gratefully acknowledged the financial support by the Helmholtz Association through the program “Science and Technology of Nanosystems” (STN), the HYIG of
References (58)
- et al.
Lead-free, air-stable ultrathin Cs3Bi2I9 perovskite nanosheets for solar cells
Sol. Energy Mater. Sol. Cells
(2018) - et al.
Low temperature solution deposited niobium oxide films as efficient electron transport layer for planar perovskite solar cell
Sol. Energy Mater. Sol. Cells
(2018) - et al.
Facile fabrication of three-dimensional TiO2 structures for highly efficient perovskite solar cells
Nano Energy
(2016) - et al.
Photonic-structured TiO 2 for high-efficiency, flexible and stable Perovskite solar cells
Nano Energy
(2019) - et al.
Nanophotonic light management for perovskite-silicon tandem solar cells
J. Photonics Energy
(2018) - et al.
Nanophotonic perovskite layers for enhanced current generation and mitigation of lead in perovskite solar cells
Sol. Energy Mater. Sol. Cells
(2019) - et al.
Simulation study on improving efficiencies of perovskite solar cell: introducing nano textures on it
Opt. Commun.
(2018) Efficiency chart
Perovskites: the emergence of a new era for low-cost, high-efficiency solar cells
J. Phys. Chem. Lett.
(2013)- et al.
Perovskite solar cells: from the atomic level to film quality and device performance
Angew. Chem. Int. Ed.
(2018)
Perovskite photonic sources
Nat. Photonics
Efficiency limit of perovskite/Si tandem solar cells
ACS Energy Lett.
Energy yield modelling of perovskite/silicon two-terminal tandem PV modules with flat and textured interfaces
Sustain. Energy Fuels
Reassessment of the limiting efficiency for crystalline silicon solar cells
IEEE J. Photovolt.
Detailed balance limit of efficiency of p-n junction solar cells
J. Appl. Phys.
Incorporation of rubidium cations into perovskite solar cells improves photovoltaic performance
Science
High-efficiency two-dimensional ruddlesden-popper perovskite solar cells
Nature
How to make over 20% efficient perovskite solar cells in regular (n-i-p) and inverted (p-i-n) architectures
Chem. Mater.
Efficient, stable and scalable perovskite solar cells using poly(3-hexylthiophene)
Nature
A universal double-side passivation for high open-circuit voltage in perovskite solar cells: role of carbonyl groups in poly(methyl methacrylate)
Adv. Energy Mater.
Record open‐circuit voltage wide‐bandgap perovskite solar cells utilizing 2d/3d perovskite heterostructure
Adv. Energy Mater.
Electron-beam-evaporated nickel oxide hole transport layers for perovskite-based photovoltaics
Adv. Energy Mater.
A wonderful electron transport layer for perovskite solar cells
Small
CH3NH3PbI3planar perovskite solar cells with antireflection and self-cleaning function layers
J. Mater. Chem. A.
Light management in perovskite solar cells and organic LEDs with microlens arrays
Opt. Express
Nanophotonic front electrodes for perovskite solar cells
Appl. Phys. Lett.
Numerical design of thin perovskite solar cell with fiber array-based anti-reflection front electrode for light-trapping enhancement
J. Opt. (United Kingdom).
Moth-eye TiO2 layer for improving light harvesting efficiency in perovskite solar cells
Small
Efficient light harvesting with micropatterned 3d pyramidal photoanodes in dye-sensitized solar cells
Adv. Mater.
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