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The efficient production of uniform, high-quality transport layers beneath the light-absorbing layer is crucial for the performance and scalability of perovskite solar cells (PSCs). This study investigates the incorporation of potassium fluoride (KF) into tin dioxide (SnO2) nanoparticle solutions to enhance the properties of the electron transport layer (ETL) in PSCs. By introducing KF, we observed a significant reduction in SnO2 particle size and improved zeta potential, resulting in a more uniform ETL. Experimental analysis demonstrated that optimal KF concentrations in SnO₂ nanoparticles improved coverage and uniformity on substrates, as confirmed by surface SEM and AFM measurement. Such improvement in ETL morphology reduced charge recombination and increased charge carrier mobility of PSCs. Specifically, PSCs with 0.02 M of KF addition showed increased power conversion efficiencies (PCE), up to 24.3%. Furthermore, large-area PSC modules with a 25 cm2 aperture area exhibited an average PCE enhancement up to 18.0% due to superior ETL uniformity. Additionally, KF addition also aided the stability enhancement, maintaining 90% of their initial efficiency after 250 hours under 60 ± 5% relative humidity. Our findings underscore the importance of ETL uniformity and provide insights into the role of KF doping in advancing PSC performance, paving the way for more efficient and scalable solar energy solutions.

Perovskite solar cells (PSCs) have attracted significant attention for their utility in next-generation energy production technology due to their rapidly increasing power conversion efficiencies (PCEs), which have recently reached levels comparable to those of commercially successful Si solar cells. The simplicity and low cost of the perovskite solution processability have further heightened their commercial viability. However, the use of N,N-dimethylformamide (DMF)─a volatile toxic solvent─in this process is considered to be a major issue that not only poses significant challenges at the lab scale but also can potentially lead to serious human and environmental damage if introduced into production lines upon being commercialized. The present study aims to address the toxicity problem by classifying solvents into green and toxic categories and using only green solvents in the solution process to create high-efficiency PSCs. A specific challenge encountered in this process was the solubility issue of perovskite materials in green solvents, which led to the creation of perovskite films with inferior optical and electrical properties. This issue was resolved by ionizing perovskite materials with the addition of organic halide materials, ultimately enabling the fabrication of PSCs with PCEs reaching up to 20.6%. The green PCE metric of all-layer green solvent PSC is as high as 4.54, exceeding that of all the green solvent-based PSCs, thereby showing that this process achieves high efficiency while addressing relevant environmental and health impacts.

Lead halide perovskite photovoltaics have shown an impressive efficiency increase over the past decade. Making this technology industrially viable requires precise optimization of every single deposition step. Here we used slot-die coating, a promising scalable deposition technique to enable large scale deposition. We demonstrate the challenges in developing high-quality slot-die coated tin oxide (SnO₂) films, suited as electron selective layers in perovskite solar cells. We studied the film quality of two commercially available colloidal SnO₂ dispersions by controlling pump rate, coating speed and temperature of the indium tin oxide substrates (ITO). The water-based dispersion was more difficult to control, but resulted in better perovskite solar cell performance than the butanol-based dispersion. Hysteresis in J–V curves from the water-based tin oxide dispersion was reduced by potassium fluoride addition. A maximum power conversion efficiency of 17.5% was achieved for MAPbI₃-based solar cells by careful optimization of the deposition parameters.

Di-(9-methyl-3-carbazolyl)-(4-anisyl)-amine is presentedas an effectivehole-transporting material suitable for application in perovskitesolar cells. It is obtained by a three-step synthesis from inexpensivestarting compounds. It has a relatively high glass transition temperatureof 93 degrees C and thermal stability with 5% weight loss at 374 degrees C.The compound exhibits reversible double-wave electrochemical oxidationbelow +1.5 V and polymerization at higher potential. A mechanism forits oxidation is proposed based on electrochemical impedance and electronspin resonance spectroscopy investigations, ultraviolet-visible-near-infraredabsorption spectroelectrochemistry results, and density functionaltheory-based calculations. Vacuum-deposited films of the compoundare characterized by a low ionization potential of 5.02 +/- 0.06eV and hole mobility of 10(-3) cm(2)/(Vs)at an electric field of 4 x 10(5) V/cm. The newly synthesizedcompound has been used to fabricate dopant-free hole-transportinglayers in perovskite solar cells. A power conversion efficiency of15.5% was achieved in a preliminary study.

Emerging technologies in solar energy will be critical in enabling worldwide society in overcoming the present energy challenges and reaching carbon net zero. Inefficient and unstable charge transport materials limit the current emerging energy conversion and storage technologies. Low-dimensional coordination polymers represent an alternative, unprecedented class of charge transport materials, comprised of molecular building blocks. Here, we provide a comprehensive study of mixed-valence coordination polymers from an analysis of the charge transport mechanism to their implementation as hole-conducting layers. Cu-II dithiocarbamate complexes afford morphology control of 1D polymer chains linked by (CuI2X2) copper halide rhombi. Concerted theoretical and experimental efforts identified the charge transport mechanism in the transition to band-like transport with a modeled effective hole mass of 6m(e). The iodide-bridged coordination polymer showed an excellent conductivity of 1 mS cm(-1) and a hole mobility of 5.8 10(-4) cm(2) (V s)(-1) at room temperature. Nanosecond selective hole injection into coordination polymer thin films was captured by nanosecond photoluminescence of halide perovskite films. Coordination polymers constitute a sustainable, tunable alternative to the current standard of heavily doped organic hole conductors.

In this work, efficient and bending durable flexible perovskite solar cells are obtained by modification of the perovskite film surface with 1- dodecanethiol (DT) followed by drop-casting of pre-dispersed thin nanosheets of MoS2. Our results show an enhancement in efficiency of the flexible device after the interface modification and revealed that the DT and MoS2 modified device recovers completely its initial values of PCE and FF, current density, and open-circuit voltage after 300 bending cycles while the standard device resembles only 50% of its PCE. Following a standard light cycling protocol for unencapsulated devices, it revealed an apparent PCE drop of the standard device up to 32% of its maximum value while the modified device recovers 95% of its highest PCE value. Different characterization methods suggest that the surface modification method induces hydrophobicity as well as significantly reduces the interface trap density.

Replacement of hole-transporting materials (HTM) for additive-free perovskite solar cells (PSCs) is an urgent issue. In this work, three new derivatives of dibenzothiophene with methoxyphenyl, trimethoxyphenyl, carbazole moieties are synthesized as hole-transporting materials for PSCs. The hole density dynamics and hole transporting properties of synthesized dibenzothiophene derivatives are investigated by combination of the charge extraction by linearly increasing voltage (CELIV) and time-of-flight (TOF) techniques. The TOF hole mobility (mu(h)) of one compound reaches the highest value of 4.2 x 10(-3) cm(2) V(-1)s(-1) at an electric field of 2.5 x 10(5) V cm(-1), however additive-free layers in PSCs did not show the best performance. Instead, the PSC efficiency is determined by a trade-off between the hole-mobility properties and the "effective" hole recombination rate k(B) ranging 0.5-40.3 ms(-1) as determined by means of the CELIV method. The best hole extraction properties are observed for a compound with mu(h) of 9.45 x 10(-4) cm(2) V(-1)s(-1) and k(B) of 11.8 ms(-1) which is coherent with its lowest energetic disorder sigma of 78.2 meV. Having both appropriate hole density dynamics and hole-transporting properties, hole-transporting layer of that compound allows to reach PCE of 20.9% for additive-free PSC, which is among the state-of-art values for devices with undoped HTM.

We report the amorphous quaternary oxide, indium-tin-silicon-oxide (ITSO), thin film as a new electron transport layer (ETL) for perovskite solar cells (PSCs). ITSO thin films are grown by magnetron co-sputtering indium-tin-oxide (ITO) and silicon oxide (SiO2) on commercial transparent conducting oxide (TCO) thin films at room temperature. As Si content increases (0-53.8 at%) the optical bandgap increases by approximately 1.3 eV and the electrical resistivity increases by six orders mainly because of the carrier concentration decrease. Consequently, the ITSO electronic structure depends largely on Si content. PSCs employing ITSO thin films as ETLs were fabricated to evaluate the effect of Si content on device performances. Si content influenced the shunt and series resistance. The optimized device was obtained using an ITSO film with 33.0 at% Si content, exhibiting 14.50% power-conversion efficiency. These results demonstrate that ITSO films are promising for developing efficient PSCs by optimizing the growing process and/or In/Sn/Si/O compositions. This approach can reduce PSC manufacturing process time and costs if ITO and ITSO are grown together by continuous sequential sputtering in a dual gun (ITO and SiO2) chamber.

The cesium cation (Cs⁺) is widely used as a dopant for highly efficient and stable formamidinium lead tri-halide perovskite (FAPbX₃, X = I, Br, Cl) solar cells. Herein, we introduce a small amount of cesium acetate (CsAc) that can effectively stabilize FAMAPbI₃ under thermal- and light illumination-stress. We show that incorporated Cs⁺ leads to relaxation of strain in the perovskite layer, and that Ac⁻ forms a strong intermediate phase with PbI₂, which can help the intercalation of the PbI₂ film with Cs⁺ and cation halide (FAI, MAI, MACl) in the sequential deposition process. The addition of CsAc reduces the trap density in the resulting perovskite layers and extends their carrier lifetime. The CsAc-modified perovskite solar cells show less hysteresis phenomena and enhanced operational and thermal stability in ambient conditions. Our findings provide insight into how dopants and synthesis precursors play an important role in efficient and stable perovskite solar cells.

Surface modification of perovskite films using a combination of 1-dodecanethiol (DT) and MoS2 nanosheets is investigated for perovskite solar cells. This surface modification is studied for two different types of perovskites, one with triple cations (CsFAMA) and one with double cations (FAMA), resulting in solar cell devices with power conversion efficiency (PCE) values of 18-19 and >20%, respectively. In both cases, stability enhancement is observed with DT and MoS2 surface modification using three different stability tracking protocols. The results reveal that by including DT and MoS2, the device retains 92% of its highest efficiency after 2200 h in dark (in air), while the standard device retained only 72%. Moreover, after light cycling, the device with DT and MoS2 retained 80%, and the standard device retained 55% of its maximum PCE. Moreover, these surface modifications gave rise to 58% decrease in the number of short-circuited devices and more reproducible results. Different characterizations revealed that the stability and efficiency enhancement is mainly due to reduced interface trap densities, improved charge transfer, and longer charge carrier lifetime. Moreover, the DT and MoS2 modifications induce hydrophobicity with an average contact angle over 80 degrees.