Here, we investigated the effect of the molecular weight (MW) of poly 3‐hexylthiophene (P3HT) hole‐transport material on the performance of perovskite solar cells (PSCs). We found that by increasing ...the MW the photovoltaic performances of the cells are enhanced leading to an improvement of the overall efficiency. P3HT‐based PSCs with a MW of 124 kDa can achieve an overall average efficiency of 16.2 %, double with respect to the ones with a MW of 44 kDa. Opposite to spiro‐OMeTAD‐based PSCs, the photovoltaic parameters of the P3HT‐based devices are enhanced by increasing the mesoporous TiO2 layer thickness from 250 to 500 nm. Moreover, for a titania scaffold layer thickness of 500 nm, the efficiency of P3HT‐based PSCs with high MW is larger than the spiro‐OMeTAD based PSCs with the same scaffold layer thickness. Recombination reactions of the devices were also investigated by voltage decay and electrochemical impedance spectroscopy. We found that the relationship between P3HT MW and cell performance is related to the reduction of charge recombination and to the increase of the P3HT light absorption by increasing the MW.
Molecular weight matters! High efficiency perovskite solar cells fabricated in ambient conditions by controlling of mesoporous (mp)‐TiO2 thickness and investigation of poly(3‐hexylthiophene) (P3HT) molecular weight (MW) as hole‐transport layer. The best efficiencies are achieved for a MW of 124 kDa and for a thickness of mp‐TiO2 of 500 nm. Efficiency enhancement is mainly related to the increase of Jsc and FF as P3HT MW increases.
This work proposes a new perovskite solar cell structure by including lithium‐neutralized graphene oxide (GO‐Li) as the electron transporting layer (ETL) on top of the mesoporous TiO2 (m‐TiO2) ...substrate. The modified work‐function of GO after the intercalation of Li atoms (4.3 eV) exhibits a good energy matching with the TiO2 conduction band, leading to a significant enhancement of the electron injection from the perovskite to the m‐TiO2. The resulting devices exhibit an improved short circuit current and fill factor and a reduced hysteresis. Furthermore, the GO‐Li ETL partially passivates the oxygen vacancies/defects of m‐TiO2 by resulting in an enhanced stability under prolonged 1 SUN irradiation.
Lithium‐neutralized graphene oxide (GO‐Li)
as electron transporting layer in perovskite solar cells is reported. The proposed device conjugates the extraordinary conduction properties of graphene based materials with the exceptional harvesting behavior of organoleadtrihalide compounds and shows enhanced power conversion efficiency and improved long term stability under operative conditions.
Designing and developing flexible electronics requires a thorough investigation of the substrates available for the fabrication of devices. Here, we present a practical study on a variety of ...significant substrates: polyethylene terephthalate (PET), its heat-stabilized (HS) derivative, HS-PET, and polyethylene naphthalate (PEN) plastic insulating films; indium tin oxide (ITO)-coated ITO/PEN and ITO/PET transparent conducting films; rigid ITO/glass and FTO/glass substrates; stainless steel and titanium foils. We put the substrates through a range of tests these actually undergo during device fabrication to determine their optical, mechanical flexibility (under different types of tensile and compressive stress bending with and without a PEDOT:PSS conducting polymer layer), solvent resistance, stability to temperature treatment (conductivity and deformation), and to UV irradiation. We highlight issues and propose solutions to improve substrate response. The results and thresholds extracted reveal limitations and windows of opportunity useful for the designer of flexible optoelectronics in determining manufacturing processes and the final applications under everyday operation.
Interface engineering is performed by the addition of graphene and related 2 D materials (GRMs) into perovskite solar cells (PSCs), leading to improvements in the power conversion efficiency (PCE). ...By doping the mesoporous TiO2 layer with graphene flakes (mTiO2+G), produced by liquid‐phase exfoliation of pristine graphite, and by inserting graphene oxide (GO) as an interlayer between the perovskite and hole‐transport layers, using a two‐step deposition procedure in air, we achieved a PCE of 18.2 %. The obtained PCE value mainly results from improved charge‐carrier injection/collection with respect to conventional PSCs. Although the addition of GRMs does not influence the shelf life, it is beneficial for the stability of PSCs under several aging conditions. In particular, mTiO2+G PSCs retain more than 88 % of the initial PCE after 16 h of prolonged 1 sun illumination at the maximum power point. Moreover, when subjected to prolonged heating at 60 °C, the GO‐based structures show enhanced stability with respect to mTiO2+G PSCs, as a result of thermally induced modification at the mTiO2+G/perovskite interface. The exploitation of GRMs in the form of dispersions and inks opens the way for scalable large‐area production, advancing the possible commercialization of PSCs.
Best of both worlds: Different graphene‐based perovskite solar cell structures are proposed to combine the extraordinary conduction properties of graphene with the exceptional lightharvesting behavior of perovskites to reach power conversion efficiency values of up to 18.2 %. Furthermore, the stability is tested under different aging conditions, and the central role of graphene‐modified interfaces in the device aging mechanisms is revealed.
Dye-sensitized solar cells (DSSCs) were assembled by using the bougainvillea flowers, red turnip and the purple wild Sicilian prickly pear fruit juice extracts as natural sensitizers of TiO(2) films. ...The yellow orange indicaxanthin and the red purple betacyanins are the main components in the cocktail of natural dyes obtained from these natural products. The best overall solar energy conversion efficiency of 1.7% was obtained, under AM 1.5 irradiation, with the red turnip extract, that showed a remarkable current density (Jsc = 9.5 mA/cm(2)) and a high IPCE value (65% at lambda = 470 nm). Also the purple extract of the wild Sicilian prickly pear fruit showed interesting performances, with a Jsc of 9.4 mA/cm(2), corresponding to a solar to electrical power conversion of 1.26%.
Metropolis Monte Carlo simulations are used to construct minimal energy configurations by electrostatic coupling of rotating dipoles associated with each unit cell of a perovskite CH3NH3PbI3 crystal. ...Short-range antiferroelectric order is found, whereas at scales of 8–10 nm, we observe the formation of nanodomains, strongly influencing the electrostatics of the device. The models are coupled to drift-diffusion simulations to study the actual role of nanodomains in the I–V characteristics, especially focusing on charge separation and recombination losses. We demonstrate that holes and electrons separate into different nanodomains following different current pathways. From our analysis we can conclude that even antiferroelectric ordering can ultimately lead to an increase of photoconversion efficiencies thanks to a decrease of trap-assisted recombination losses and the formation of good current percolation patterns along domain edges.
Perovskite Solar Cells (PSCs) are well known for their high efficiencies under 1 sun (AM1.5G), however, PSC can also generate power by harvesting the low‐light available indoors. Here, three flexible ...PSC architectures are presented for indoor applications: with a metal electrode aiming for high efficiency; carbon electrode aiming for high stability and compatibility with large‐scale production; and hole transport material (HTM)‐free carbon for simplifying the fabrication process. A maximum efficiency of 30.9% (30.0%) under 1000 lux (200 lux) is obtained for a PSC with gold electrode. A maximum efficiency of 25.4% (24.7%) and 23.1% (22.3%) is obtained for the carbon devices with and without HTM, respectively, under 1000 lux (200 lux). To the best of the author's knowledge, the efficiency values presented here for a device with a carbon‐based electrode, with and without HTM, are the record values for a flexible PSC at indoor light conditions. Furthermore, the HTM‐free carbon device kept 84% of its initial efficiency after 1000 h at MPPT and lost virtually no performance after 1000 h at 85 °C. Also, non‐encapsulated devices of all configurations withstood 1600 h in air with a maximum loss in efficiency of 6%.
A flexible perovskite solar cell for indoor applications is fabricated. A record efficiency of 31% and 25%, and 23% at 1000 lux (393.6 W cm−2) is obtained for a device with an electrode of metal, carbon and carbon with no hole extraction layer, respectively. Carbon devices lost only 20% of its initial efficiency after 1000 h under Maximum Power Point Tracking.
Solar cells (SCs) are the most ubiquitous and reliable energy generation systems for aerospace applications. Nowadays, III–V multijunction solar cells (MJSCs) represent the standard commercial ...technology for powering spacecraft, thanks to their high‐power conversion efficiency and certified reliability/stability while operating in orbit. Nevertheless, spacecraft companies are still using cheaper Si‐based SCs to amortize the launching costs of satellites. Moreover, in recent years, new SCs technologies based on Cu(In,Ga)Se2 (CIGS) and perovskite solar cells (PSCs) have emerged as promising candidates for aerospace power systems, because of their appealing properties such as lightweightness, flexibility, cost‐effective manufacturing, and exceptional radiation resistance. In this review the current advancements and future challenges of SCs for aerospace applications are critically discussed. In particular, for each type of SC, a description of the device's architecture, a summary of its performance, and a quantitative assessment of the radiation resistance are presented. Finally, considering the high potential that 2D‐materials (such as graphene, transition metal dichalcogenides, and transition metal carbides, nitrides, and carbonitrides) have in improving both performance and stability of SCs, a brief overview of some important results concerning the influence of radiation on both 2D materials‐based devices and monolayer of 2D materials is also included.
The growing interest of governments and private companies in space exploration is pushing the development of highly efficient and low‐cost solar cells for applications in extraterrestrial environments. This review provides an overview of the pros and cons of both commercially available and new promising photovoltaic technologies for space applications.
MXenes are a recent family of 2D materials with very interesting electronic properties for device applications. One very appealing feature is the wide range of work functions shown by these ...materials, depending on their composition and surface terminations, that can be exploited to adjust band alignments between different material layers. In this work, based on density functional theory calculations, how mixed terminations of F, OH, and/or O affect the work function of Ti3C2 MXene is analyzed in detail, covering the whole phase‐space of mixtures. The Ti3C2/CH3NH3PbI3 (MAPbI3) perovskite coupled system for solar cell applications is also analyzed. A strong nonlinear behavior is found when varying the relative concentrations of OH, O, and F terminations, with the strongest effect of the OH groups in lowering the work function, already at a relative amount of 25%. A surprising minimum work function is found for relative OH:O fraction of 75:25, explained in terms of the nonlinear electronic response in screening the surface dipoles.
Herein, how F, OH, and O mix terminations affect the work function of the Ti3C2/MAPbI3 interface is studied, covering the whole phase‐space of mixtures and highlighting the mechanism of strong nonlinear behaviors. Using first‐principles calculations, the degree and origin of the work function non‐linearity is described and sized.
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