In this paper, oleylammonium polysulfides molecules were self-assembled on an etched perovskite film, leading to an enhancement in moisture stability of the devices.
Organometallic halide perovskite solar cells (PSCs) are rapidly evolving as the promising photovoltaic technologies with high record efficiency over 24%. The inorganic p‐type semiconductor NiOx is extensively used as important hole transport layers for the realization of stable and hysteresis‐free solar cells due to their good electronic properties, facile fabrication, and excellent chemical endurance. However, the critical issues of NiOx films including poor intrinsic conductivity and mismatched band alignment limit further improvement of the device performance. Herein, it is demonstrated that a versatile alkaline earth metal (Mg, Ca, Sr, and Ba) doping strategy can effectively engineer the electronic properties of NiOx contacts in inverted planar PSCs. Alkaline earth metal doping can deepen valence band maximum and enhance the hole conductivity of NiOx films, which better aligns the energy band in solar cells. The champion device based on Sr‐doped NiOx films attains a power conversion efficiency of 19.49% with a high open‐circuit voltage (VOC) of 1.14 V for NiOx‐based CH3NH3PbI3 devices. The resulted device shows negligible hysteresis and high stability as well. This finding provides a systematic doping strategy to further improve the performance of inverted planar PSCs.
Passivation, as a classical surface treatment technique, has been widely accepted in start-of-the-art perovskite solar cells (PSCs) that can effectively modulate the electronic and chemical property of defective perovskite surface. The discovery of inorganic passivation compounds, such as oxysalts, has largely advanced the efficiency and lifetime of PSCs on account of its favorable electrical property and remarkable inherent stability, but a lack of deep understanding of how its local configuration affects the passivation effectiveness is a huge impediment for future interfacial molecular engineering. Here, we demonstrate the central-atom-dependent-passivation of oxysalt on perovskite surface, in which the central atoms of oxyacid anions dominate the interfacial oxygen-bridge strength. We revealed that the balance of local interactions between the central atoms of oxyacid anions (e.g., N, C, S, P, Si) and the metal cations on perovskite surface (e.g., Pb) generally determines the bond formation at oxysalt/perovskite interface, which can be understood by the bond order conservation principle. Silicate with less electronegative Si central atoms provides strong O-Pb motif and improved passivation effect, delivering a champion efficiency of 17.26% for CsPbI2Br solar cells. Our strategy is also universally effective in improving the device performance of several commonly used perovskite compositions.
The
insertion of organic spacers into halide perovskite slabs has
offered a trade-off between the efficiency and stability of perovskite
solar cells (PSCs). The layered structure of diammonium-intercalated
cesium lead halide perovskites is virtually unexplored, in contrast
to several works on the monoammonium system. In this report, we find
that perovskite with 1,4-butanediammonium (BDA) and cesium cations
can only form n = 1 and n = 2 layered
isologues defined by the chemical formula of (BDA)Cs
n–1Pb
n
(I0.7Br0.3)3n+1, while the n = 3–4 ones will self-construct into unique heterostructures
comprising separated quantum wells (QWs; n = 1–2)
and 3D (n = ∞) perovskites. We highlight that
the 2D/3D heterostructures show a structural resemblance to that of
bulk heterojunction in organics, thus improving the charge separation
and transport more than surface passivation. Solar cells based on
the (BDA)Cs3Pb4I9.1Br3.9 (n = 4) absorbing layer delivered a power conversion
efficiency (PCE) reaching 9.49% with ideal light and thermal stability.
Perovskite solar cells (PSCs) are expected to profoundly impact the photovoltaic society on account of its high-efficiency and cost-saving manufacture. As a key component in efficient PSCs, the hole transport layer (HTL) can selectively collect photogenerated carriers from perovskite absorbers and prevent the charge recombination at interfaces. However, the mainstream organic HTLs generally require multi-step synthesis and hygroscopic dopants that significantly limit the practical application of PSCs. Here, a self-organized percolative architecture composed of narrow bandgap oxides (e.g., Co 3 O 4 , NiO, CuO, Fe 2 O 3 , and MnO 2 ) and wide bandgap SrCO 3 oxysalt as efficient HTLs for PSCs is presented. The percolation of dual phases offers nanosized hole transport pathways and optimized interfacial band alignments, enabling significantly improved charge collection compared with the single phase HTLs. As a consequence, the power conversion efficiency boosted from 8.08% of SrCO 3 based device and 15.47% of Co 3 O 4 based device to 21.84% of Co 3 O 4 -SrCO 3 based one without notable hysteresis. The work offers a new direction by employing percolative materials for efficient charge transport and collection in PSCs, and would be applicable to a wide range of opto-electronic thin film devices.
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