Light‐Induced Degradation of Perovskite Solar Cells: The Influence of 4‐Tert‐Butyl Pyridine and Gold

Abstract

Stability is one of the key challenges for industrial scale commercialization of perovskite solar cells. In this work, a degradation mechanism that depends on materials and bias conditions of the device during light‐soaking is proposed. The observed degradation is linked to the additive 4‐tert‐butyl pyridine (tBP), crucial to the hole transport layer of most perovskite solar cells, and gold. This conclusion is reached through the statistical analysis of multiple compositional profiles of light‐soaked and nonlight‐soaked devices and by selective replacement of material layers of the device. Moreover, the rate of the light‐induced degradation is enhanced by operation at forward bias, which is required for power generation. Thus, this work stresses the need for the development of transport layers that do not require tBP, and to replace gold to produce high‐performing devices that are also stable under operating conditions.

A structure–property study of fluoranthene-cored hole-transporting materials enables 19.3% efficiency in dopant-free perovskite solar cells

“…All these factors contribute to an inferior long-term operational stability of the derived PVSCs. 11,12 On one hand, using inorganic HTMs to replace the organic counterparts seems to be a feasible solution to address this shortage since they generally possess higher hole mobility and chemical stability than the latter. 13 Nevertheless, most of the inorganic HTMs require harsh processing conditions that are incompatible with perovskites, which impedes the fabrication of efficient PVSCs especially for the n-i-p device conguration.…”

Highly efficient all-inorganic perovskite solar cells with suppressed non-radiative recombination by a Lewis base

“…It is noteworthy that most of the high-performance inorganic PVSCs reported so far are based on using the conventional n-i-p architecture, where a doped hole-transporting layer (HTL), like Spiro-OMeTAD, is employed. However, severe degradation processes have been reported for devices using such doped HTLs due to the instability of dopants (e.g., 4-tert-butyl pyridine and lithium salts) [18][19][20][21] . In this regard, the development of inverted pi-n inorganic PVSCs is very attractive, since it not only can exempt the use of these unstable doped HTLs, but also be more compatible with the fabrication of tandem solar cells because most of perovskite-perovskite tandem solar cells are fabricated with the p-i-n architecture to date 22,23 .…”

Barrier Designs in Perovskite Solar Cells for Long‐Term Stability

“…[43] Furthermore, at elevated temperature and under long-term illumination, inward diffusion of electrode metal materials, even the noble Au, can induce electronic contamination of perovskites or active species of interfacial layers, resulting in inferior device stability. [61][62][63][64] For example, Domanski et al demonstrated the severe diffusion of Au through Spiro-OMeTAD into the perovskite at 70 °C, which created deep trap states in perovskite, inducing serious degradation of PSCs. [62] Guerrero et al reported the observation of S-shape curves in J-V measurements for Ca, Al, Ag, and Au electrodes-based PSCs, which can be attributed to the chemical degradation of metal electrode contacts.…”

“…Several works have revealed the instability of Ag as electrode as discussed in the introduction part. [60][61][62][63][64] To retard the reaction of Ag with halide in perovskite, our group recently demonstrated a bilayer Bi/Ag electrode in inverted PSCs to prevent both inward moisture/Ag and outward iodine ions (Figure 13d). [234] We found that the Bi electrode prevented an oriented 2D structure benefiting for the compact-morphology formation (Figure 13e).…”