For more than a decade, the power conversion efficiency (PCE) of halide perovskite solar cells (PSCs) has risen rapidly from 3.85% to 25.6%, making the technology the youngest member of the High Efficiency Photovoltaic Alliance. Halide perovskites have significant advantages in terms of process versatility, allowing for low-cost manufacturing. However, most of these reported high-efficiency PSCs are in small areas (< 1 cm2) and require further process engineering to achieve industrial-scale production while minimizing PCE losses. Moreover, the general manufacturing method of laboratory-scale (<1 cm2) perovskite solar cells (PSCs) is generally not scalable, and the control of large-area perovskite layer crystallization in commercial-sized modules is particularly challenging.
Scholars from Nanyang Technological University demonstrated a seed-assisted crystallization method: a homogeneous and highly crystalline large-area Cs0.15FA0.85Pb (I0.83Br0.17)3 (CsFA) perovskite film by adding alkali salts CsPbBr3 and KBb2Br5 to the ink of the perovskite precursor. X-ray photoelectron spectroscopy reveals segregation of potassium ions at the SnO2/perovskite interface, which is the nucleation site of perovskite layer crystallization. Uniformly grooved mold coated CsFA films (100 cm2) from additives containing precursor inks have larger particles and therefore enhanced photoelectric properties, and the corresponding devices exhibit greater reproducibility and consistency. Under 1 solar exposure, the device efficiency of the slot mold coating PSCs of the n-type/intrinsic/p-type structure is 18.94%, and the stability is improved, and the initial efficiency is maintained after 1150 hours of testing at 65°C. The cell-mold-coated methylammonium-free perovskite module has an effective area of 57.5 cm2 and an efficiency of 16.22%, maintaining 82% of its initial efficiency after 4800 hours at 30% relative humidity without encapsulation. The article was published in Advanced Functional Materials under the title "Alkali Additives Enable Efficient Large Area (>55 cm2) Slot-Die Coated Perovskite Solar Modules."
Thesis Link:
https://doi.org/10.1002/adfm.202113026
Figure 1. a) X-ray crystal structure of KPb 2 Br 5 lead bromide. b) Schematic diagram of a precursor solution containing CsPbBr3/KPb 2 Br5 clusters and [PbI 6] 4-octahedron and DMF, DMSO solvent molecules. c) DLS curves of CsPbBr 3, KPb 2 Br 5, CsFA, CsPbBr 3 -CsFA and KPb 2 Br 5 -CsFA precursor solutions. d) XRD profiles of CsFA, CsPbBr 3-CsFA and KPb 2 Br 5-CsFA perovskite films.
Figure 2.a) J-V curve of the devices of CsFA, CsPbBr 3-CsFA, and KPb 2 Br 5-CsFA PS. b) EQE spectra with integrated Jsc curves with CsFA, CsPbBr 3-CsFA, and KPb 2 Br5-CsFA devices. c) Statistical results for a total of 30 PCE devices from a batch of CsFA, CsPbBr 3 -CsFA, and KPb 2Br 5 -CsFA PSCs. d) Forward and reverse scan J-V curves of KPb 2 Br 5-CsFAPSC. e) Normalized EL spectra at different voltages.
Figure 3. a) XPS depth profile obtained on A KPb 2 Br 5-CsFA perovskite film on FTO glass with Ar gas ions (10 keV Ar + 1000). The illustration shows the same depth profile focused on the mixed perovskite/substrate interface. b) The Pb 4f, I 3d, Cs 3d and K2p core levels of KPb 2 Br 5-CsFA perovskite films evolve with the etching cycle. c,d) Normalized K2p and Br 3d spectra of different brominides (KBr, KPb 2 Br 5 and hybridized lead and titanium).
Figure 4. Coordinated custom perovskite ink for perovskite film groove mold coating. a) Schematic of a perovskite film coated with a N2 knife-assisted (N2-knife-assisted) suture mold using a coordination custom ink at 10.8 mm s-1 and 56 °C. The illustration shows images of coated perovskite inks, perovskite/interlayers, and perovskite films. b) Schematic diagram of perovskite/interlayer and fully crystallized perovskite film after perovskite ink drying. c) UV-visible absorption in 9 different areas of 10 × 10 cm 2 glass/perovskite substrate. d) J-V curve of the best performance KPb 2 Br 5-CsFA perovskite solar module. e) Device performance statistics for CsFA, CsPbBr3-CsFA, and KPb 2 Br 5-CsFA PSC modules.
Figure 5.a) Stability of CsFA and KPb 2Br 5-CsFA perovskite devices with 10,000 hours of storage at room temperature protected from light at 30% RH (no package). b) Thermal stability (no package) of CsFA and KPb 2 Br 5-CsFA perovskite devices over 1000 hours at 65 °C. c) Thermal stability of CsFA and KPb 2 Br 5 -CsFA perovskite devices over 900 hours at 85 °C (PIB-based blanket package). d) Stability of the CsFA and KPb 2 Br 5-CsFA perovskite micromodules, stored for more than 4500 hours at room temperature and 30% RH protected from light (no package).
This paper demonstrates a seed-assisted crystallization method for large-area suture mold coatings of CsFA perovskite films by adding alkali metal salts, CsPbBr3, and KPb2Br5 to perovskite precursor inks. These additives not only form homogeneous and highly crystalline perovskite films, but also improve photoelectric properties. These additives can be used as seeds for perovskite growth and grow larger perovskite grains with better photovoltaic properties, and PCE mapping substrates over 100 cm2 can be prepared to indicate high uniformity and uniform coating of perovskite films. Thus, PSCs in an n-i-p structure prepared from an additive containing precursor inks provide an optimal efficiency of 18.94% (0.09 cm2 effective area) under 1 standard sunlight exposure, with negligible hysteresis and impressive stability, of which 82% remains unchanged after 1150 hours of initial testing at 60 °C. The corresponding slot-coated methylammonium-free perovskite solar module showed an optimal efficiency of 16.22% with an effective area of 57.5 cm2 maintaining 82% of its initial efficiency after 4800 hours at 30% RH without encapsulation. This paper demonstrates that this seed-assisted crystallization method for perovskite thin film formation will provide profound insights into scalable and repeatable manufacturing processes that are key to the industrialization of perovskite photovoltaic technology. (Text: SSC)
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