Spectral Dependence of Degradation under Ultraviolet Light in Perovskite Solar Cells

Abstract

Perovskite solar cells (PSCs) demonstrate excellent power conversion efficiencies (PCEs) but face severe stability challenges. One key degradation mechanism is exposure to ultraviolet (UV) light. However, the impact of different UV bands is not yet well established. Here, we systematically study the stability of PSCs on the basis of a methylammonium lead iodide (CHNHPbI) absorber exposed to (i) 310-317 (UV-B range) and (ii) 360-380 nm (UV-A range), under accelerated conditions. We demonstrate that the investigated UV-B band is detrimental to the stability of PSCs, resulting in PCE degradation by more than 50% after an exposure period >1700 sun-hours. This finding is valid for architectures with a range of electron transport layers, including SnO, compact-TiO, electron-beam TiO, and nanoparticle-TiO. We also show that photodegradation is apparent for high, as well as for low illumination intensities of UV-B light, but not for illumination with UV-A wavelengths. Finally, we show that degradation of PSCs is preventable at the cost of a small fraction of photocurrent by using UV-filtering or luminescent downshifting layers.

Electron‐Beam‐Evaporated Nickel Oxide Hole Transport Layers for Perovskite‐Based Photovoltaics

“…The solar cell is kept at an elevated temperature of 75 °C, which simulates an operation of the device under a more extreme stress condition, a solar cell has to withstand-at least as peak condition. [22,[72][73][74][75] It was shwon before that UV radiation degrades perovskite solar cells at the front side interface of the metal oxide charge transport material and the perovskite absorber layer. More important, the output voltage is not altered significantly while tracking, demonstrating a stable position of the MPP and less influence of the small hysteresis present in the devices.…”

“…More important, the output voltage is not altered significantly while tracking, demonstrating a stable position of the MPP and less influence of the small hysteresis present in the devices. [22,74,75] Titanium dioxide (TiO x ), in particular, exhibits strong UV degradation and is usually not recommended to be placed in front of the perovskite absorber without UV blocking layers. [21][22][23] Taking this into account, electron beam evaporated NiO x as an HTL is improving the device robustness against temperature stress, which is usually the only stress factor that is not limited during outdoor operation but a common problem for devices employing organic HTLs like spiro-MeOTAD or PTAA.…”

“…[21][22][23] Taking this into account, electron beam evaporated NiO x as an HTL is improving the device robustness against temperature stress, which is usually the only stress factor that is not limited during outdoor operation but a common problem for devices employing organic HTLs like spiro-MeOTAD or PTAA. [22,74,75,78] Thus, the use of alternative front side oxides next to TiO x and SnO x absorbing the UV radiation without changing the chemical properties of the layer might be of key importance to overcome this limiting factor. [22,[72][73][74][75] It was shwon before that UV radiation degrades perovskite solar cells at the front side interface of the metal oxide charge transport material and the perovskite absorber layer.…”

“…[1][2][3][4][5] Even though other optoelectronic devices like light emitting diodes and lasers are being researched, [6][7][8][9][10][11][12][13] perovskite-based photovoltaics (PV) is the key technology driving the fast emergence of perovskitebased optoelectronics. [21][22][23] Most reported record PCEs are still based on highly expensive organic hole transport layer (HTL) materials like 2,2′,7,7′-tetrakis[N,N-di (4methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-MeOTAD) or poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA). [14] Despite the rapid progress in terms of PCE, one key challenge of perovskite-based PV is still its low stability under realistic outdoor stress conditions-temperature, humidity, and ultraviolet (UV) radiation.…”

Halide Perovskite Nanocrystals for Next‐Generation Optoelectronics

“…However, UV‐induced damage specifically related to PDs is not very well documented in the literature. On the other hand, studies on the UV‐degradation of PSCs, and possible solution to enhance their lifespan, are widely available . It is worth highlighting that, both for PSCs and PDs, further studies to clarify the effects of reversible and irreversible UV‐induced degradation mechanisms under realistic experimental conditions are urgently needed .…”