Efficient light harvesting from flexible perovskite solar cells under indoor white light-emitting diode illumination

This is the first report of an investigation on flexible perovskite solar cells for artificial light harvesting by using a white light-emitting diode (LED) lamp as a light source at 200 and 400 lx, values typically found in indoor environments. Flexible cells were developed using either low-temperature sol–gel or atomic-layer-deposited compact layers over conducting polyethylene terephthalate (PET) substrates, together with ultraviolet (UV)-irradiated nanoparticle TiO2 scaffolds, a CH3NH3PbI3–xClx perovskite semiconductor, and a spiro-MeOTAD hole transport layer. By guaranteeing high-quality carrier blocking (via the 10–40 nm-thick compact layer) and injection (via the nanocrystalline scaffold and perovskite layers) behavior, maximum power conversion efficiencies (PCE) and power densities of 10.8% and 7.2 μW·cm–2, respectively, at 200 lx, and 12.1% and 16.0 μW·cm–2, respectively, at 400 lx were achieved. These values are the state-of-the-art, comparable to and even exceeding those of flexible dye-sensitized solar cells under LED lighting, and significantly greater than those for flexible amorphous silicon, which are currently the main flexible photovoltaic technologies commercially considered for indoor applications. Furthermore, there are significant margins of improvement for reaching the best levels of efficiency for rigid glass-based counterparts, which we found was a high of PCE ~24% at 400 lx. With respect to rigid devices, flexibility brings the advantages of being low cost, lightweight, very thin, and conformal, which is especially important for seamless integration in indoor environments.</p

Atomic layer deposition of NiO applied in a monolithic perovskite/PERC tandem cell

Monolithic perovskite/silicon tandem photovoltaics have fueled major research efforts as well as gaining rapid industrial interest. So far, most of the literature has focused on the use of currently more expensive silicon heterojunction bottom cell technology. This work demonstrates a perovskite/silicon tandem solar cell based on the industrially dominant passivated emitter and rear cell (PERC) technology. In detail, we investigate a tunnel recombination junction (TRJ) consisting of ITO/NiO/2-(9H-carbazol-9-yl)ethyl] phosphonic acid (2PACz) and compare it with an ITO/2PACz TRJ. Specifically, the NiO layer is deposited by atomic layer deposition (ALD). Although ITO/2PACz-based tandem devices can reach more than 24% conversion efficiency, we observe that they suffer from a large spread in photovoltaic parameters due to electrical shunts in the perovskite top cell, caused by the inhomogeneity of the 2PACz layer on ITO. Instead, when ALD NiO is sandwiched between 2PACz and ITO, the surface coverage of 2PACz improves and the yield of the devices, in terms of all device parameters, also improves, i.e., the standard deviation decreases from 4.6% with ITO/2PACz to 2.0% with ITO/NiO/2PACz. In conclusion, thanks to the presence of NiO, the TRJ consisting of ITO/NiO/2PACz leads to a 23.7% efficient tandem device with narrow device efficiency distribution

Data on dopant characteristics and band alignment of CdTe cells with and without a ZnO highly-resistive-transparent buffer layer

Photovoltaic enhancement of cadmium telluride (CdTe) thin film solar cells using a 50 nm thick, atomic-layer-deposited zinc oxide (ZnO) buffer film was reported in “Enhancement of the photocurrent and efficiency of CdTe solar cells suppressing the front contact reflection using a highly-resistive ZnO buffer layer” (Kartopu et al., 2019) [1].Data presented here are the dopant profiles of two solar cells prepared side-by-side, one with and one without the ZnO highly resistive transparent (HRT) buffer, which displayed an open-circuit potential (Voc) difference of 25 mV (in favor of the no-buffer device), as well as their simulated device data. The concentration of absorber dopant atoms (arsenic) was measured using the secondary ion mass spectroscopy (SIMS) method, while the density of active dopants was calculated from the capacitance-voltage (CV) measurements. The solar cell simulation data was obtained using the SCAPS software, a one-dimensional solar cell simulation programme. The presented data indicates a small loss (around 20 mV) of Voc for the HRT buffered cells

Enhancement of the photocurrent and efficiency of CdTe solar cells suppressing the front contact reflection using a highly-resistive ZnO buffer layer

We report on the effects of using an atomic layer deposited ZnO transparent buffer layer with > 106 Ω cm resistivity on the performance of CdZnS/CdTe solar cells grown by metalorganic chemical vapour deposition (MOCVD). The buffer film thickness is adjusted by optical modelling to suppress the reflection losses at the front contact. A clear improvement, up to 1.8% in conversion efficiency, was obtained in comparison to reference devices without the ZnO buffer layer, thanks to the enhancement of the current density (Jsc) and fill factor (FF). Device spectral response showed improved collection for most of the visible region. Reflectance measurements confirmed that the ZnO film reduced the optical reflectance around the transparent front contact. This effect permitted light management through the front contact leading to an improvement of the Jsc and hence the photovoltaic conversion efficiency. These results are intriguing since the literature on CdTe solar cells did not previously report improvement to the photocurrent and device response through controlling the highly-resistive transparent buffer layer

Plasma assisted atomic layer deposition of nickel oxide as hole transport layer for hybrid perovskite solar cells

Low-temperature atomic layer deposition (ALD) offers significant merits in terms of processing uniform, conformal and pinhole-free thin films, with sub-nanometer thickness control. In this work, plasma-assisted atomic layer deposition (ALD) of nickel oxide (NiO) is carried out by adopting bis-methylcyclopentadienyl-nickel (Ni(MeCp)2) as precursor and O2 plasma as co-reactant, over a wide table temperature range of 50-300 °C. A growth rate of 0.32 Å per cycle is obtained for films deposited at 150 °C with an excellent thickness uniformity on a 4 inch silicon wafer. Bulk characteristics of the NiO film together with its interfacial properties with a triple cation hybrid perovskite absorber layer are comprehensively investigated, with the aim of integrating NiO as hole transport layer (HTL) in a p-i-n perovskite solar cell (PSC) architecture. It is concluded that “key” to efficient solar cell performance is the post-annealing treatment of the ALD NiO films in air, prior to perovskite synthesis. Post-annealing leads to better wettability of the perovskite layer and increased conductivity and mobility of the NiO films, delivering an increase in short-circuit current density (Jsc) and fill factor (FF) in the fabricated devices. Overall, a superior 17.07% PCE is achieved in the post-annealed NiO-based PSC when compared to the 13.98% PCE derived from the one with pristine Ni

High-performance flexible perovskite solar cells exploiting Zn2SnO4 prepared in solution below 100 degrees C

Fabricating inorganic-organic hybrid perovskite solar cells (PSCs) on plastic substrates broadens their scope for implementation in real systems by imparting portability, conformability and allowing high-throughput production, which is necessary for lowering costs. Here we report a new route to prepare highly dispersed Zn2SnO4 (ZSO) nanoparticles at low-temperature (<100 degrees C) for the development of high-performance flexible PSCs. The introduction of the ZSO film significantly improves transmittance of flexible polyethylene naphthalate/indium-doped tin oxide (PEN/ITO)-coated substrate from similar to 75 to similar to 90% over the entire range of wavelengths. The best performing flexible PSC, based on the ZSO and CH3NH3PbI3 layer, exhibits steady-state power conversion efficiency (PCE) of 14.85% under AM 1.5G 100 mW . cm(-2) illumination. This renders ZSO a promising candidate as electron-conducting electrode for the highly efficient flexible PSC applications.ope

The AGILE Mission

AGILE is an Italian Space Agency mission dedicated to observing the gamma-ray Universe. The AGILE's very innovative instrumentation for the first time combines a gamma-ray imager (sensitive in the energy range 30 MeV-50 GeV), a hard X-ray imager (sensitive in the range 18-60 keV), a calorimeter (sensitive in the range 350 keV-100 MeV), and an anticoincidence system. AGILE was successfully launched on 2007 April 23 from the Indian base of Sriharikota and was inserted in an equatorial orbit with very low particle background. Aims. AGILE provides crucial data for the study of active galactic nuclei, gamma-ray bursts, pulsars, unidentified gamma-ray sources, galactic compact objects, supernova remnants, TeV sources, and fundamental physics by microsecond timing. Methods. An optimal sky angular positioning (reaching 0.1 degrees in gamma- rays and 1-2 arcmin in hard X-rays) and very large fields of view (2.5 sr and 1 sr, respectively) are obtained by the use of Silicon detectors integrated in a very compact instrument. Results. AGILE surveyed the gamma- ray sky and detected many Galactic and extragalactic sources during the first months of observations. Particular emphasis is given to multifrequency observation programs of extragalactic and galactic objects. Conclusions. AGILE is a successful high-energy gamma-ray mission that reached its nominal scientific performance. The AGILE Cycle-1 pointing program started on 2007 December 1, and is open to the international community through a Guest Observer Program