Solution processable direct bandgap copper-silver-bismuth iodide photovoltaics : compositional control of dimensionality and optoelectronic properties

Altres ajuts: SRR acknowledges the support from "laCaixa" Foundation (ID 100010434; LCF/BQ/PI20/11760024). Open access publishing facilitated by Monash University, as part of the Wiley - Monash University agreement via the Council of Australian University Librarians.The search for lead-free alternatives to lead-halide perovskite photovoltaic materials resulted in the discovery of copper(I)-silver(I)-bismuth(III) halides exhibiting promising properties for optoelectronic applications. The present work demonstrates a solution-based synthesis of uniform CuAgBiI thin films and scrutinizes the effects of x on the phase composition, dimensionality, optoelectronic properties, and photovoltaic performance. Formation of pure 3D CuAgBiI at x = 1, 2D CuAgBiI at x = 2, and a mix of the two at 1 < x < 2 is demonstrated. Despite lower structural dimensionality, CuAgBiI has broader optical absorption with a direct bandgap of 1.89 ± 0.05 eV, a valence band level at -5.25 eV, improved carrier lifetime, and higher recombination resistance as compared to CuAgBiI. These differences are mirrored in the power conversion efficiencies of the CuAgBiI and CuAgBiI solar cells under 1 sun of 1.01 ± 0.06% and 2.39 ± 0.05%, respectively. The latter value is the highest reported for this class of materials owing to the favorable film morphology provided by the hot-casting method. Future performance improvements might emerge from the optimization of the CuAgBiI layer thickness to match the carrier diffusion length of ≈40-50 nm. Nonencapsulated CuAgBiI solar cells display storage stability over 240 days

Acridine-based novel hole transporting material for high efficiency perovskite solar cells

An acridine-based hole transporting material (ACR-TPA) without the spirobifluorene motif is synthesized via non complicated steps. The ACR-TPA film including Li-TFSI and 4-tert-butylpyridine (tBP) additives exhibits a hole mobility of 3.08 x 10(-3) cm(2) V-1 s(-1), which is comparable to the mobility of the classical spiro-MeOTAD (2.63 x 10(-3) cm(2) V-1 s(-1)), and its HOMO level of -5.03 eV is slightly lower than that of spiro-MeOTAD (-4.97 eV). ACR-TPA layers with different thicknesses are applied to MAPbI3 perovskite solar cells, where power conversion efficiency (PCE) increases as the ACR-TPA layer thickness increases due to increased recombination resistance and fast charge separation. The best PCE of 16.42% is achieved from the ca. 250 nm-thick ACR-TPA, which is comparable to the PCE of 16.26% for a device with spiro-MeOTAD in the same device configuration. It is thus anticipated that ACR-TPA can be a promising alternative to spiro-MeOTAD because of its lower cost and comparable photovoltaic performance

Lewis acid-base adduct-type organic hole transport material for high performance and air-stable perovskite solar cells

Since hole transport materials (HTMs) play a significant role in enhancing the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs), which are the key factors for their commercialization, an effective design strategy is necessary for the potential HTMs in the current emerging field of PSCs. Here, we present a new class of HTM with pyridine as a central core with an extended pi-conjugated molecular structure with electron-donating blocks. We have systematically investigated its photophysical, thermal, electrochemical, and charge transport properties and found that 4,4&apos;-(5,5&apos;-(pyridine-2,6-diylbis(4,1-phenylene))bis(thiophene-5,2-diyl))bis (N,N-bis(4-methoxyphenyl)aniline) (PyThTPA) is a potential HTM candidate for making PSCs. The PyThTPA HTM-based PSC attained an average PCE of 16.57% with outstanding long-term durability of over 720 hrs with minimal reduction of its initial PCE and negligible hysteresis. This PSC performance was 34% higher than that of the state-of-the-art HTM, Spiro-OMeTAD with tris(pentafluorophenyl)borane (BCF). We speculate that the Lewis acid-base adduct (LABA) formation of pyridine in the HTM and BCF interacted with methylammonium lead iodide (MAPbI(3)), resulting in the MAPbI(3)/HTM interface becoming more selective for holes. This also enhanced the film uniformity and afforded a smoother morphology with improved hydrophobicity that further increased the long-term durability. Furthermore, the mobility and conductivity were increased for PyThTPA with BCF. To the best of our knowledge, this is the first report of pyridine being incorporated into the HTM with continuous pi-conjugation and with a high performance of nearly 17%. Overall, we believe that this approach will be an effective design strategy capable of enhancing the performance of PSCs with less hysteresis and improved long-term durability.11Nsciescopu