Although the power conversion efficiency of perovskite solar cells has increased from 3.81% to 22.1% in just 7 years, they still suffer from stability issues, as they degrade upon exposure to moisture, UV light, heat, and bias voltage. We herein examined the degradation of perovskite solar cells in the presence of UV light alone. The cells were exposed to 365 nm UV light for over 1,000 h under inert gas at <0.5 ppm humidity without encapsulation. 1-sun illumination after UV degradation resulted in recovery of the fill factor and power conversion efficiency. Furthermore, during exposure to consecutive UV light, the diminished short circuit current density (Jsc) and EQE continuously restored. 1-sun light soaking induced recovery is considered to be caused by resolving of stacked charges and defect state neutralization. The Jsc and EQE bounce-back phenomenon is attributed to the beneficial effects of PbI2 which is generated by the decomposition of perovskite material.

Flexible perovskite solar cells (FPSCs) have various applications such as wearable electronic textiles and portable devices. In this work, we demonstrate FPSCs on a titanium metal substrate employing solution-processed silver nanowires (Ag NWs) as the top electrode. The Ag NW electrodes were deposited on top of the spiro-MeOTAD hole transport layer by a carefully controlled spray-coating method at moderate temperatures. The power conversion efficiency (PCE) reached 7.45 % under AM 1.5 100 mW cm(-2) illumination. Moreover, the efficiency for titanium-based FPSCs decreased only slightly (by 2.6 % of the initial value) after the devices were bent 100 times. With this and other advances, fully solution-based indium-free flexible photovoltaics, advantageous in terms of price and processing, have the potential to be scaled into commercial production.

Organometallic halide perovskite solar cells (PSCs) have unique photovoltaic properties for use in next-generation solar energy harvesting systems. The highest efficiency of PSCs reached 22.1% on a laboratory scale of <0.1 cm device area. Thus, scaling up is the next step toward commercialization, but the difficulty in controlling the quality of large-area perovskite thin films remains a fundamental challenge. It has also been frequently reported that the J- V hysteresis is intensified in PSCs with areas larger than 1 cm. In this study, we have fabricated a large-area perovskite layer using PbICl films, providing an intrinsic porous layer and enhancing the uniformity of the perovskite layer at areas larger than 1 cm. Furthermore, we have investigated the polymeric properties of the prevalent hole-transporting material poly(triarylamine) (PTAA) with its photovoltaic performance. Two types of PTAAs, poly[bis(4-phenyl)(2,4-dimethylphenyl)amine] and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], were compared. A series of PTAAs with different molecular weights ( M) and polydispersity indices were studied, as the molecular weight of the PTAA is a key factor in determining the electrical properties and photovoltaic performance of the system. The fabricated PSCs with an aperture area of 1 cm based on a high-molecular-weight PTAA achieved a power conversion efficiency of 16.47% with negligible hysteresis and excellent reproducibility.

Methylammonium lead iodide (CH 3 NH 3 PbI 3 ) perovskite solar cell in a flexible fiber shape is developed via a fully dipping process with a mixed solvent of N,N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) followed by toluene dipping. We introduce the first-ever effective n-type compact layer through facile anodizing of titanium wire, achieving a considerable power conversion efficiency of 3.85%, which remains stable during bending; spray-deposited silver nanowires (Ag NWs) are used as the top electrode instead of gold. The ease of fabrication, low cost of materials, and all-solid-state structures result in a simple approach to developing electronic textiles for harvesting solar energy and blazes a new trail in the field of fiber-shaped photovoltaics.

Planar perovskite solar cells (PSCs) incorporating n‐type SnO2 have attracted significant interest because of their excellent photovoltaic performance. However, the film fabrication of SnO2 is limited by self‐aggregation and inhomogeneous growth of the intermediate phase, which produces poor morphology and properties. In this study, a self‐controlled SnO2 layer is fabricated directly on a fluorine‐doped tin oxide (FTO) surface through simple and rapid chemical bath deposition. The PSCs based on this hydrolyzed SnO2 layer exhibit an excellent power conversion efficiency of 20.21 % with negligible hysteresis. Analysis of the electrochemical impedance spectroscopy on the charge transport dynamics indicates that the bias voltage influences both interfacial charge transportation and the ionic double layer under illumination. The hydrolyzed SnO2‐based PSCs demonstrate a faster ionic charge response time of 2.5 ms in comparison with 100.5 ms for the hydrolyzed TiO2‐based hysteretic PSCs. The results of quasi‐steady‐state carrier transportation indicate that a dynamic hysteresis in the J–V curves can be explained by complex ionic‐electronic kinetics owing to the slow ionic charge redistribution and hole accumulation caused by electrode polarization, which causes an increase in charge recombination. This study reveals that SnO2‐based PSCs lead to a stabilized dark depolarization process compared with TiO2‐based PSCs, which is relevant to the charge transport dynamics in the high‐performing planar SnO2‐based PSCs.

The high electron mobility, wide band gap, and chemical stability of n-type SnO2 have facilitated its use as an ideal electron transport layer (ETL) for perovskite solar cells (PSCs). However, the tendency of SnO2 to aggregate during film formation leads to poor morphology and low reproducibility. Despite important advances in the application of SnO2 for PSCs, a thorough understanding of material control over aggregation is lacking. Herein, aggregation-regulated SnO2 films are directly deposited on a fluorine-doped tin oxide glass surface via chemical bath deposition using retarding agents with multiple functional OH groups. Density functional theory calculations confirm the increase in stabilized binding energies of the Sn precursors by the retarding agents. Investigation of the morphology and topography of the SnO2 films reveals that manipulating the physicochemical properties of interacting molecules regulates SnO2 particle aggregation. The chemical states and energy-band properties of the fabricated SnO2 films are found to depend on the retarding agent used in the Sn precursors. The aggregation-regulated SnO2 layer prepared using glycerol exhibits an optimal morphology, a few oxygen vacancies, and a high work-function energy level. A device fabricated using the glycerol–SnO2 film as an ETL achieves a high efficiency of 21.8%, negligible hysteresis, and a reduced potential loss.

larger acceptance owing to their decreasing cost. However, Si cells feature power conversion efficiencies (PCEs) close to the maximum practically achievable value (29.4% for crystalline Si solar cells), which makes it difficult to further reduce the levelized cost of electricity by decreasing the power output-to-cost ratio. [7,8] The most straightforward solution to this problem is to hybridize multiple semiconductor layers in a tandem architecture for absorbing the different wavelengths of the solar spectrum using different solar cell technologies. [9-12] As proven by a theoretical tandem cell efficiency of ≈46%, [13] Si solar cells with a bandgap of 1.1 eV have been regarded as potential bottom subcells of hybrid tandems, additionally offering the benefits of mass production suitability owing to well-organized production lines and global supply chains. [13,14] However, Sibased hybrid tandem solar cells configured with cost-effective solar cell technologies, including dye-sensitized solar cell (DSSC) and organic photovoltaics (OPV), have far lower efficiencies than single-junction Si solar cells, predominantly because of the insufficient compatibility of the employed materials with Si solar cells. [15-19] Metal halide perovskite-based solar cells have attracted significant attention in recent years because of their potential to be processed at low cost, high efficiencies, excellent optoelectronic properties, and tunable bandgap. They have therefore considered as prospective components of hybrid tandems. [20] Previous studies on the fundamental working principle of the hydrogenated amorphous Si (a-Si:H)/a-Si:H tandem and related validation by empirical investigations show the feasibility of combining different solar cell technologies, [6,21-23] as exemplified by the pairing of high-bandgap perovskite subcells with low-bandgap Si subcells or the assembly of dual perovskitebased tandem solar cells exploiting perovskite bandgap tunability. [14,24-26] To date, considerable effort has been directed at the development of wide-bandgap perovskite solar cells (PSCs) (1.65-1.8 eV) for hybrid tandem applications, [27,28] and remarkable progress (i.e., a high open-circuit voltage (V oc) of 1.31 V with a wide bandgap of 1.72 eV (>90% of the Shockley-Queisser limit)) has been achieved. [29] Currently, researchers aim to realize perovskite-based hybrid tandem solar cells with PCEs of 30%. Nonetheless, considerable electrical property and fabrication process adjustments are required to integrate singlejunction perovskites into the hybrid tandem architecture. The introduction of an intermediate layer to bridge different solar Hybrid tandem solar cells offer the benefits of low cost and full solar spectrum utilization. Among the hybrid tandem structures explored to date, the most popular ones have four (simple stacking design) or two (terminal/tunneling layer addition design) terminal electrodes. Although the latter design is more cost-effective than the former, its widespread application is hindered by the difficulty of preparing...

Iodide-free tribromide-based perovskites, with their wide bandgap of over 2.0 eV, are highly regarded as potential candidates for a photoelectrochemical water splitting system and the topmost cell in tandem solar cell. Herein, we report on the importance of microtuning of the crystal lattice by cesium incorporation into the A-site on low temperature processed formamidinium lead tribromide (CH(NH 2 ) 2 PbBr 3 = FAPbBr 3 ) perovskite films. The partial incorporation of cesium bromide (CsBr) into the FAPbBr 3 film tunes crystal-lattice interactions, resulting in a high-purity cubic crystal system with preferred orientation. An entirely low temperature processed planar photovoltaic device assembled with FAPbBr 3 containing 8% Cs (Cs 0.08 FA 0.92 PbBr 3 ) exhibited an optimum PCE (power conversion efficiency) of 8.56% with a V oc (open-circuit voltage) of 1.516 V, which is higher than the PCE of 7.07% and V oc of 1.428 V of the FAPbBr 3 device. Photoluminescenceintensity and temporal-imaging measurements were conducted by laser scanning confocal time-resolved microscopy (LCTM), which revealed that CsBr incorporation into a FAPbBr 3 film significantly suppresses the nonradiative recombination pathways and homogenizes the spatial distribution of photoluminescence. It was visualized that the incorporation of CsBr in FAPbBr 3 directly affects the bulk defect and photoluminescence properties, which provides evidence that Cs ions surely alleviate the segregation and aggregation of ions in the perovskite film. Notably, the Cs 0.08 FA 0.92 PbBr 3 film, with a carrier lifetime of about 270 ns, exhibited a 1.37-fold longer radiative recombination time than that (210 ns) observed for the FAPbBr 3 film. Furthermore, aging experiments without encapsulation under ambient (in air for 2000 h) and severe (65 °C and 65% RH for 500 h) conditions revealed that the Cs 0.08 FA 0.92 PbBr 3 devices were more robust than the FAPbBr 3 devices.