Spray-coating
is a scalable and time-efficient technique for the
development of large-area metal halide perovskite (MHP) solar cells.
However, a bottleneck still exists toward the development of fully
scalable n-i-p-type
MHP solar cells particularly on spray-coating the hole transporting
layer (HTL). Here, we present a reliable strategy of spray-coating
the HTL by using MoO2 nanoparticles with small amounts
of poly(triarylamine) (PTAA) binders to ensure uniform coverage and
efficient charge extraction. By spray-coating all layers except the
Au electrode, we achieve high and scalable efficiencies of 14.26 and
13.88% for CsPbI2Br unit cells (0.12 cm2) and
submodules (25 cm2), respectively. We then extend toward
an all-spray-coating process by spray-coating carbon black as the
top counter electrode, resulting in a submodule efficiency of 10.08%.
Finally, we also demonstrate good long-term stability of the submodules
under damp heat conditions (85 °C/85% relative humidity) over
1000 h.
Aesthetics
is just as important as efficiency when it comes to
designing solar cells for building-integrated photovoltaic applications
such as solar windows, thus recently instigating a great interest
in the development of neutral-colored semitransparent solar cells.
Organic–inorganic halide perovskites (OIHPs) are of particular
interest due to their unique properties as solar cell materials. Here,
we demonstrate a laser patterning process of the OIHP film to control
aperture ratios, which in turn can produce a neutral color for view.
Through careful aperture control and by using indium tin oxide as
the top electrode, we are able to fabricate neutral-colored semitransparent
OIHP solar cells with high efficiency. Furthermore, we show that the
involvement of a LiF interlayer at the OIHP and electron transporting
layer interface is necessary, since the LiF interlayer plays a bifunctional
role of interface passivation and current flow rectification, in order
to more closely simulate an ideal diode. As a result, we successfully
demonstrate a high efficiency of 12.83% for a 2.00 cm2 area
and 9.30% for a 36.00 cm2 area, while achieving an average
visible range transmittance of 21.74%.
Formamidinium lead triiodide (FAPbI 3 ) with stable black perovskite phase and without significantly changing its bandgap is demonstrated by the incorporation of CaCl 2 . More incorporated CaCl 2 in FAPbI 3 creates a desirable crystal structure, satisfying the Goldschmidt tolerance factor, and thereby stabilizing black perovskite phase under ambient conditions. However, more incorporated CaCl 2 in FAPbI 3 is likely to degrade the perovskite due to its hygroscopic characteristics. In addition, the incorporated CaCl 2 in FAPbI 3 solution reduces solubility, causing the formation of smaller crystal grains and pinholes due to quick precipitation during the non-solvent dripping crystallization process. Accordingly, 5 % CaCl 2 incorporated FAPbI 3 films have the best phase stability and solar cell performance with 18.0 % of power conversion efficiency at 1 sun condition.
TiO 2 has been widely adopted as an electron transport layer during the fabrication of efficient metal halide perovskite solar cells (MHP-SCs). In this study, we prepared acetylacetone (Acac)-modulated TiO 2 nanoparticles (NPs) suitable for low-temperature solution processing via the sol-gel method. Acac coordinates with TiO 2 NPs and preferably passivates surface trap states which are detrimental to photovoltaic performance. Moreover, the Acac-TiO 2 NPs establish a favorable band alignment for charge extraction by donating the lone pair electron. As a result, Acac-TiO 2 NPs based MHP-SCs exhibit an outstanding power conversion efficiency (PCE) of 21.20% attributed to facilitated charge extraction and reduced defect density. Furthermore, by implementing lowtemperature solution-processable Acac-TiO 2 NPs, we successfully demonstrated a remarkable PCE of 18.01% along with excellent mechanical stability, retaining 74.5% and 67.1% PCE after 5000 bending cycles in outward and inward directions from Acac-TiO 2 NPs based MHP-SCs on a flexible substrate.
To investigate the synergistic effect of perylene diimide (PDI) unit and diphenyl‐o‐carboranyl (Cb) group, PDI–Cb with Cb groups at the bay positions of the PDI unit is synthesized. By introducing 3D carboranyl group into the bay position, PDI–Cb shows distorted geometry between PDI core and the adjacent phenyl ring of Cb due to the ring torsions, which can suppress the aggregation tendency. Furthermore, the proper lowest unoccupied molecular orbital (LUMO) energy level of −4.12 eV may be beneficial to extract electrons from the perovskite efficiently. By introducing PDI–Cb interlayer at perovskite/C60 interface, the inverted perovskite solar cells (PSCs) have significantly enhanced efficiency from 19.98% to 22.31% at 1 sun condition (AM1.5G 100 mW cm−2) because the PDI–Cb interlayer promotes charge extraction thanks to the electron‐accepting ability of Cb group; thereby, it reduces carrier recombination significantly. In addition, the unencapsulated inverted PSC with the PDI–Cb interlayer has good photo‐ and thermal stability because it shows 9.3% efficiency degradation after continuous 1 sun light soaking for 1000 h at 85 °C in N2 atmosphere.
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