Hole Transport Bilayer for Highly Efficient and Stable Inverted Perovskite Solar Cells

Abstract

We demonstrate that using a hole transport bilayer composed of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) and CuI leads to highly efficient and stable inverted, that is, p−i−n, perovskite solar cells (PSCs). The bilayerbased devices had an average power conversion efficiency (PCE) of 19.4% and a maximum PCE of 20.34%. In comparison, devices with a single PTAA interlayer showed an average PCE of 17.7%. Perovskite films fabricated on PTAA/CuI bilayers showed improved crystallinity and larger grain sizes. Data from ultraviolet photoelectron spectroscopy and Mott−Schottky analysis of impedance suggest an increased built-in potential within the device with enhanced upward band bending at the CuI interface. The bilayered HTL devices have minimum current−voltage hysteresis and stable current output at the maximum power point. These devices were stable for more than 4500 h under ambient light in an inert atmosphere.

Deleterious Effects of Halides and Solvents used in Electronic Device Fabrication on the Integrity of Copper Iodide Thin‐Films**

“…When we fabricated a prototypical hybrid perovskite, methylammonium lead triiodide (MAPbI 3 ), using MAI/PbI 2 over a thin film of CuI, the powder X‐diffraction (PXRD) pattern did not show peaks attributable to CuI (Figure 2). This observation is consistent with many reports that contain the absence of peaks related to CuI in the PXRD [10b–d,g,h] . Often, the lack of peaks from CuI is attributed to the dominance of the peaks from the perovskite [10b] .…”

PTAA as Efficient Hole Transport Materials in Perovskite Solar Cells: A Review

“…Band bending introduced by this multilayer system also enhances the efficiency of carrier collection. [ 193 ] Moreover, PTAA with anionic conjugated polyelectrolytes interlayers, which were initially aimed at benefiting the perovskite coverage, also improves the V OC of the devices owning to the additional passivation functions from the interlayer. [ 175 ] So far, interlayers have been reported to smoothen the band alignment, improve the conductivity, enhance the surface wetting, and control the grain growth.…”

Copper Bromide Hole Transport Layer for Stable and Efficient Perovskite Solar Cells

“…Inorganic p-type semiconductor HTLs have been investigated in recent years as they are stable, have high hole mobility and charge collection, and can be fabricated with simple and low-cost processes. − In particular, cuprous salts such as copper thiocyanate (CuSCN) and copper iodide (CuI) have shown promising potential to replace organic HTLs in p–i–n PSCs. − However, both CuSCN and CuI have limitations. CuSCN is a coordination polymer.…”