NiO_x‐Seeded Self‐Assembled Monolayers as Highly Hole‐Selective Passivating Contacts for Efficient Inverted Perovskite Solar Cells

Abstract

Self‐assembled monolayers (SAMs) have emerged as effective carrier transport layers in perovskite (PVK) solar cells because of their unique ability to manipulate interfacial property, as well as simple processing and scalable fabrication. However, the defects and pinholes derived from their sensitive adsorption process inevitably deteriorate the final device performance. Herein, a sputtered nickel oxide (NiOx) interlayer is used as a seed layer to promote the adsorption of the [2‐(3,6‐dimethoxy‐9H‐carbazol‐9‐yl)ethyl]phosphonic acid (MeO‐2PACz) SAM on the indium tin oxide (ITO) substrate. The promoted adsorption is attributed to the enhanced tridentate binding between MeO‐2PACz and NiOx relative to the conventional bidentate binding between MeO‐2PACz and ITO. In addition, the NiOx modification can simultaneously improve the passivation ability and hole‐selectivity of the MeO‐2PACz, provide a favorable energy‐level alignment at the ITO/PVK interface, and prevent a direct contact between PVK and ITO. As a consequence, this NiOx‐seeded MeO‐2PACz hole transport layer enables a significantly enhanced power conversion efficiency of 19.9% in comparison with 18.4% of the control device. This work provides an effective strategy to improve the performance of the SAM‐based photoelectric device.

Surface Passivation of Sputtered NiOx Using a SAM Interface Layer to Enhance the Performance of Perovskite Solar Cells

“…The result shows that NiO x passivates the ITO and prevents direct contact between perovskite and ITO, which contributes to improving the PCE. 50 Herein, we developed a similar strategy using sp-NiO x by coating MeO-2PACz on top of sp-NiO x to study the surface defect of NiO x and perovskite interfaces using different analytical techniques with the commonly used perovskite methylammonium lead iodide (MAPbI3). Despite these remarkable contributions, the application of MeO-2PACz, by modulating the crystal contact or layer between NiO x /perovskite, needs more investigation.…”

“…Lastly, Sun et al developed a method to enhance the interaction between MeO-2PACz and ITO using a sputtered NiOx layer with triple-cation perovskite devices. The result shows that NiO x passivates the ITO and prevents direct contact between perovskite and ITO, which contributes to improving the PCE . Herein, we developed a similar strategy using sp-NiO x by coating MeO-2PACz on top of sp-NiO x to study the surface defect of NiO x and perovskite interfaces using different analytical techniques with the commonly used perovskite methylammonium lead iodide (MAPbI3).…”

Simultaneous Interfacial Modification and Defect Passivation for Wide‐Bandgap Semitransparent Perovskite Solar Cells with 14.4% Power Conversion Efficiency and 38% Average Visible Transmittance

“…Based on the results of UPS, EDS and XPS, it can be speculated that ultrathin 2PACz self-assembles on the surface of NiO x film as exhibited in Figure 2c, tuning the characteristic of NiO x tremendously. [30] The contact angles of water on the surface of NiO x films with or without the modification layer displaying in Figure 2d,e have a great change, confirming 2PACz influences the hydrophilic property of NiO x tremendously. The inferior hydrophilic property of 2PACz compared with NiO x makes perovskite only nucleate on some places of the 2PACz surface, thus the perovskite can grow with compact grain.…”

“…Based on the results of UPS, EDS and XPS, it can be speculated that ultrathin 2PACz self‐assembles on the surface of NiO x film as exhibited in Figure 2c, tuning the characteristic of NiO x tremendously. [ 30 ]…”

Operational stability, low light performance, and long-lived transients in mixed-halide perovskite solar cells with a monolayer-based hole extraction layer

“…Record e ciencies for both single junction and tandem solar cells have been recently achieved by coating the transparent oxide substrates with these molecular monolayers. [24][25][26] It has also been reported that perovskite layers deposited on SAM-treated substrates are resilient toward halide segregation. [24] We wanted to explore the stability and performance of the monolayer-based device stack with both wide and narrow gap absorbers.…”