Ultraviolet Photocatalytic Degradation of Perovskite Solar Cells: Progress, Challenges, and Strategies

Abstract

Perovskite solar cells (PSCs) have received great attention due to their ever-increasing power conversion efficiency (PCE), low-cost materials, and easy solution preparation. The certified efficiency of PSCs reached 25.5% [1] based on a lab scale, exceeding the performance of copper indium gallium selenide (CIGS) and CdTe thin-film solar cells and approaching the highest reported value of the mainstream silicon solar cell. [2] The highest-efficiency devices generally use the regular n-i-p structure composed of a perovskite absorber between a metal oxide electron transport layer (MOETL) and an organic hole transport layer (HTL). [1,3] Miyasaka et al. first adopted CH 3 NH 3 PbI 3 and CH 3 NH 3 PbBr 3 as light absorbers in liquid electrolyte-based dyesensitized solar cells using a thick TiO 2 layer (%10 μm) as an electron collector. The first PSCs achieved a PCE of 3.8%. [4] After that, tremendous efforts have been made for the PSCs based on TiO 2 . The PSCs included an n-type TiO 2 ETL, a perovskite absorber layer, a p-type 2,2 0 ,7,7 0tetrakis-(N,N-di-4-methoxyphenylamino)-9,9 0 -spirobifluorene (Spiro-OMeTAD) HTL, which has been the most typical and successful structure. Grätzel et al. achieved the first certified efficiency of 14.14% based on the aforementioned n-i-p structure with compact TiO 2 (c-TiO 2 )/mesoporous TiO 2 (m-TiO 2 ). [5] In the following years, the performance of the PSCs based on TiO 2 achieved tremendous progress. To remove the organic material in TiO 2 paste and achieve high-quality m-TiO 2 layer, a hightemperature sintering process (>500 C) was generally needed. [6] To avoid high-temperature processing, low-temperature processed SnO 2 was developed. Tian and co-workers adopted SnO 2 thin films attained by spin coating SnO 2 nanoparticles on indium-doped tin oxide (ITO) followed by low-temperature annealing at 200 C, and a 13% PCE was achieved. [7] Huge progress of SnO 2 -based PSCs was reported by Fang and co-workers. They adopted thermal decomposition of SnCl 2 •2H 2 O precursor at 180 C in ambient air to form SnO 2 film and achieved 17.21% efficiency. [8] Later on, Hagfeldt et al. used low-temperature chemical bath deposition to grow SnO 2 ETL and obtained almost hysteresis-free PCEs of 20.8%. [9] In 2019, the PCE of the planar SnO 2 PSCs reached a certified efficiency of 23.32%, which first surpassed that of m-TiO 2 PSCs. [10] Therefore, SnO 2 has increasingly attracted great attention as an ETL for PSCs, and it is considered as the most promising alternative to TiO 2 . Up to date, all the world records of the certified PCE were achieved based on TiO 2 or SnO 2 n-i-p conventional structures since the PSCs appeared in 2009 (Figure 1). [1,3,5,6,[10][11][12][13][14][15] Recently, a PCE of 25.8% (certified 25.5%) has been achieved based on Cl-bonded SnO 2 . [1] Thus, the important key to achieve state-of-the-art PSCs is the application of TiO 2 or SnO 2 , due to its excellent electrical properties.

Multifunctional Metal‐Organic Frameworks Capsules Modulate Reactivity of Lead Iodide toward Efficient Perovskite Solar Cells with UV Resistance

“…Currently, apart from photovoltaic performance, the stability of PVSCs is a crucial factor for their commercialization, particularly in terms of UV stability. [51,52] When exposed to UV and O 2 simultaneously, the deterioration of the labile perovskite structure can be catastrophic. The intense absorption of ZIF-8 in the UV region suggests that the ZIF-8@FAI interlayer can serve as a DC layer to protect the PVSCs device (Figure 6a).…”

Smart Window Structures Based on Highly Conductive, Transparent Metal Nanomeshes and Thermochromic Perovskite Films

“…Several studies have addressed the UV degradation of the perovskite layer which could lead to the release of volatile I 2 and CH 3 NH 3 I (MAI) from perovskite structure. [26,27] Additionally, Shlenskaya et al discovered that the UV-induced precipitation of I 2 and MAI would further form a new (MA) 2 Au 2 I 6 phase in the perovskite film which is in direct contact with Au thin film. [28] Therefore, a thin, wide bandgap (3.2-3.4 eV) metal oxide material as a synergistic protective layer needs to be incorporated in between metal mesh and perovskite layers to improve the photo-and chemicalstability of thermochromic smart window devices.…”

“…Several studies have addressed the UV degradation of the perovskite layer which could lead to the release of volatile I 2 and CH 3 NH 3 I (MAI) from perovskite structure. [ 26,27 ] Additionally, Shlenskaya et al. discovered that the UV‐induced precipitation of I 2 and MAI would further form a new (MA) 2 Au 2 I 6 phase in the perovskite film which is in direct contact with Au thin film.…”

UV-robust and efficient perovskite solar cells enabled by interfacial photocatalysis suppression and defect passivation

“…[4][5][6] In particular, UV light constitutes approximately 3-5% of the total solar spectrum and is an unavoidable factor in the practical application of solar cells. 7 While moisture and oxygen erosion can be readily isolated through encapsulation, the harmful effects of UV irradiation cannot be eliminated under working conditions, particularly in plateau and space environments. 8,9 Therefore, addressing the issue of perovskite absorber degradation caused by UV exposure is crucial for successful commercialization.…”