Design of SnO₂ Electron Transport Layer in Perovskite Solar Cells to Achieve 2000 h Stability Under 1 Sun Illumination and 85 °C

Abstract

In order for the perovskite solar cells to be truly commercialized, long-term stability of the device must be guaranteed; hence, the individual layers with each interface is of prominent importance. [10][11][12][13] In this aspect, electron transport layer (ETL) and its interface with the perovskite is one of the important sites, which ultimately determines the performance and the stability of the device, since defects generated in the bulk of ETL or accumulated at the ETL/perovskite interface can both damage the charge extraction property and stability of the device, by trapping photogenerated carriers and providing degradation sites. [14][15][16][17] Moreover, for the typical normal n-i-p type device, the ETL side of the device is constantly exposed to the incident light, which can initiate photoinduced degradation or light-induced thermal stress on the device. [18][19][20] Therefore, it is important to smartly design an ETL that can maintain long-term stability under the operation condition.Tin oxide is one of the most widely used materials for ETL due to its high conductivity and appropriate Fermi energy relative to the perovskite. SnO 2 layer can also be easily fabricated by a simple spin-coating of commercially available nanoparticle-type SnO 2 colloidal dispersion, which results in thin and compact layer of stacked SnO 2 nanoparticles applicable to various device structures. [21][22][23][24][25] Here, defects or degradation sites may arise from the inherent defects from the SnO 2 nanoparticle, dangling bonds at the nanoparticle surface from imperfect film formation, or mismatch between nanoparticles and perovskite lattice. [26][27][28][29] To address these issues, various additive compounds have been incorporated into the SnO 2 layer, ranging from ionic salts to chained organic molecules with specialized functional groups. [30][31][32][33][34][35][36] Another alternative method is to synthesize compact SnO 2 layer by using tin (II) chloride hydrate (SnCl 2 •xH 2 O) as a precursor. [37][38][39] Some research groups have even fabricated bilayer-type SnO 2 ETL to improve the film quality, consisting of bare and additivemodified SnO 2 nanoparticles, or nanoparticle-type and SnCl 2derived SnO 2 . [40][41][42] Despite the modified ETLs show merits of passivating charge-trapping defects, these methods require sequential deposition steps for the fabrication of ETLs with multiple heat treatments at different temperatures, which adds

Molecular Engineering of Azahomofullerene-based Electron Transporting Materials for Efficient and Stable Perovskite Solar Cells

“…Since the past decade, three-dimensional hybrid organic–inorganic lead halide perovskites (LHPs) have inspired scientists in the field of optoelectronic devices due to their extraordinary optoelectronic properties. , There is particular attention on the application of LHPs as light absorber materials in the next generation of thin film photovoltaic technology, and so-called perovskite solar cells (PSCs) have emerged as a “rising star” due to their high-power conversion efficiency (PCE) exceeding 25%, low cost, and facile fabrication techniques. – To date, highly efficient PSCs are achieved on the regular n–i–p device architecture, in which the surface morphology and chemistry of the electron transport layer (ETL) can affect the deposition and quality of the perovskite layer. , Among various n-type semiconducting materials, SnO 2 stands out as a promising ETL in n–i–p PSCs due to its low-temperature processable synthesis, high optical transmittance, superior electron mobility, and proper band energy alignment with the perovskites . However, the presence of defects (e.g., oxygen vacancy defects) and dangling bonds on the surface of SnO 2 can enhance the nonradiative recombination at the SnO 2 /perovskite interface, affecting device performance and stability. , In this context, many strategies have been undertaken to passivate the surface defects of SnO 2 ETLs to enhance the device’s photovoltaic performance and stability. – This includes doping of the SnO 2 ETL with various metal ions – and interface modification with ionic salts, , organic molecules, , polymers, self-assembled molecules, – or carbon materials …”

Double‐Side Passivation of Perovskite Solar Cells for High Performance and Stability

“…These defects, such as ionic substitution, interstitials, and vacancies, can lead to nonradiative recombination, trap state formation, and reduced carrier mobility, which can lower the performance of PSCs. [23][24][25][26][27][28][29][30][31] Surface passivation is a potential approach to improve both the photovoltaic performance and stability of PSCs by suppressing defects in the light absorption layer. [32][33][34][35] Among the surface treatment materials, organic halide salt is mainly used for the post-treatment of PSCs due to its similarity with the organic cation of perovskite constituent.…”

Low Damage Scalable Pulsed Laser Deposition of SnO2 for p–i–n Perovskite Solar Cells

“…[1] SnO 2 owns superior properties such as high spectral transmittance (E g = 3.6-4.2 eV), high electron mobility, and favorable energy band alignment with halide perovskites and fullerene-based charge transport layers. [2][3][4] Moreover, it is earth abundant, can be processed via several methods, and shows excellent mechanical, thermal, chemical, and UV-light stability [5][6][7][8][9][10] The reported perovskite/Si and perovskite/CIGS tandems have integrated SnO 2 in both n-i-p and p-i-n solar cell configurations. In the case of n-i-p perovskite/Si tandems, low thermal processing (<200 °C for silicon heterojunction bottom cell) and conformal deposition of SnO 2 are required to ensure full coverage of the textured surface of the bottom Si cell.…”