Printable and Homogeneous NiO_x Hole Transport Layers Prepared by a Polymer‐Network Gel Method for Large‐Area and Flexible Perovskite Solar Cells

Abstract

As one of the most promising hole transport layers (HTLs), nickel oxide (NiO x ) has received extensive attention due to its application in flexible largearea perovskite solar cells (PSCs). However, the poor interface contact caused by inherent easy-agglomeration phenomenon of NiO x nanoparticles (NPs) is still the bottleneck for achieving high-performance devices. Herein, a general strategy to synthesize NiO x NPs with high crystallinity and good dispersibility via the polymer network micro-precipitation method is reported. Promisingly, this approach realizes the flow-division of precipitant and the restraint of the NPs motion, thereby effectively alleviating the coagulation phenomenon caused by excessive local concentration and secondary movement adsorption. Furthermore, the addition of ionic liquid not only inhibits the secondary aggregation of NiO x NPs during the dispersion process, but also significantly enhances the properties of the colloidal solution. Ultimately, the 1.01 cm 2 PSCs based on the optimized NiO x HTLs achieve the champion power conversion efficiency of 20.91% and 19.17% on rigid and flexible substrates, respectively. Moreover, the reproducibility and stability of PSCs are also significantly improved, especially for flexible devices. Overall, this strategy provides the possibility for flexible, large-area fabrication of high-quality NiO x HTLs to promote the development of stable and efficient perovskite devices.

Elimination of Interfacial Lattice Mismatch and Detrimental Reaction by Self‐Assembled Layer Dual‐Passivation for Efficient and Stable Inverted Perovskite Solar Cells

“…The variation of chemical state also alters the corresponding energy level. [12] From the ultraviolet photoelectron spectroscopy (UPS) of secondary electron cut-off and valence bands (Figure 1d,e and Figure S3a,b, Supporting Information), the Fermi level (E F ) values of NiO x and NiO x /CBSA can be calculated about −4.80 and −5.02 eV, and the energy gap between valence band maximum (VBM) and E F narrows from 0.41 to 0.31 eV after CBSA treatment, which is beneficial for increasing the hole concentration. Moreover, the VBM levels of NiO x and NiO x /CBSA are −5.21 and −5.33 eV, respectively.…”

“…[7][8][9][10][11] Nickel oxide (NiO x ) nanocrystals as a promising stable hole transporting layer (HTL) in inverted p-i-n PVSCs are less prone to hysteresis and work well with flexible or tandem architectures. [12] Nevertheless, the PCE of NiO x -based inverted devices are usual inferior to the organic regular counterparts owing to the several interfacial issues: i) abundant surface traps and mismatch energy level restrict the charge carrier extraction, causing large energy offset; [13] ii) the redox reaction between Ni 3+ and A-site cation salts form a PbI 2 -rich hole extraction barrier, leading to severe interfacial destruction; [14] iii) inconsistent thermal expansion of lattice units in NiO x and perovskite results in tensile strain, prejudicing the microstructure and accelerating the degradation of perovskite. [15][16][17] Therefore, it is urge to solve these issues for performance enhancement and commercialization application of NiO x -based PVSCs.Recently, a great deal of molecular interlayers have been applied to passivate or adjust the energy level of NiO x /perovskite interface for strengthen the efficiency and stability in p-i-n devices, such as inorganic salts, [18][19][20] acids, [21] fullerene derivatives [22] and polymers buffer layer.…”

Doping Free and Amorphous NiOx Film via UV Irradiation for Efficient Inverted Perovskite Solar Cells

“…Additionally, the preparation of NiO x nanocrystals ink has a complex procedure (centrifugation, vacuum drying, redispersing, etc.). [ 8 , 10 ] These obstacles hamper the mass fabrication and promising applications of NiO x film for flexible devices. Therefore, it is yet a crucial challenge to facilely prepare effective NiO x HTLs at temperatures <150 °C.…”

Heterostructure Silicon Solar Cells with Enhanced Power Conversion Efficiency Based on Six/Ni3+ Self-Doped NiOx Passivating Contact

“… 12 Recently, hole-selective contacts using MoO x 6 , 8 and VO x 13 , 14 with a high work function have demonstrated their success in improving cell performance, achieving the high PCE of 23.5% 6 and 21.6%, 13 respectively. NiO x is more abundant and stable and exhibits a wide band gap and p -type conductivity, which has been widely studied and applied as hole transport layer materials in perovskite solar cells 15 , 16 and dye-sensitized solar cells. 17 The large conduction band offset (Δ E c ) and the small valence band offset (Δ E V ) from c -Si enable NiO x to extract the hole while blocking the electrons.…”