Inverted perovskite solar cells with transparent hole transporting layer based on semiconducting nickel oxide

Perovskite (CH3NH3PbI3) solar cells (PSCs) were produced in the inverted architecture employing transparent nickel oxide (NiO) as hole transporting layer (HTL). The different functional layers of the photoconversion device were solution processed in ambient conditions the HTL of NiO being prepared via sol-gel and successively deposited by spin-coating. The conditions of preparation of the transparent HTL were optimized through the stabilization of the nickel-containing sol with bulky alcohols and strong inorganic acids. The photoactive layer of CH3NH3PbI3 was deposited in air at high relative humidity (ca. 50-60%). The electron selective contact was constituted by spin coated 3H-cyclopropa[1,9] [5,6]fullerene-C60-Ih-3'-butanoic acid 3'-phenyl methyl ester (PCBM) with solution processed 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine, BCP) as interlayer. The deposition of CH3NH3PbI3 in ambient conditions as well as the processing of the BCP interlayer from solution simplified enormously the entire procedure of device fabrication. The largest value of photoconversion efficiency (PCE) we achieved with the inverted architecture photocells was 14 % with an average PCE of 12 %. The solar cells displayed an hysteresis-free behavior with excellent time stability of the maximum power output

High-Efficiency Perovskite Solar Cell Based on Poly(3-Hexylthiophene): Influence of Molecular Weight and Mesoscopic Scaffold Layer

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

Progress, highlights and perspectives on NiO in perovskite photovoltaics

The power conversion efficiency of NiO based perovskite solar cells has recently hit a record 22.1%. Here, the main advances are reviewed and the role of NiO in the next breakthroughs is discussed

Interface and Composition Analysis on Perovskite Solar Cells.

Organometal halide (hybrid) perovskite solar cells have been fabricated following four different deposition procedures and investigated in order to find correlations between the solar cell characteristics/performance and their structure and composition as determined by combining depth-resolved imaging with time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), and analytical scanning transmission electron microscopy (STEM). The interface quality is found to be strongly affected by the perovskite deposition procedure, and in particular from the environment where the conversion of the starting precursors into the final perovskite is performed (air, nitrogen, or vacuum). The conversion efficiency of the precursors into the hybrid perovskite layer is compared between the different solar cells by looking at the ToF-SIMS intensities of the characteristic molecular fragments from the perovskite and the precursor materials. Energy dispersive X-ray spectroscopy in the STEM confirms the macroscopic ToF-SIMS findings and allows elemental mapping with nanometer resolution. Clear evidence for iodine diffusion has been observed and related to the fabrication procedure.We acknowledge Lucio Cinà, Simone Casaluci, Stefano Razza and Narges Yaghoobi Nia for the technical support, “Polo Solare Organico” Regione Lazio, the “DSSCX” MIUR-PRIN2010 and FP7 ITN “Destiny” for funds. G.D., S.C. and C.D. acknowledge funding from ERC under grant number 259619 PHOTO EM. C.D. acknowledges financial support from the EU under grant number 312483 ESTEEM2.This is the final version of the article. It was first available from ACS via http://dx.doi.org/10.1021/acsami.5b0803

The golden fig: a plasmonic effect study of organic-based solar cells

An optimization work on dye-sensitized solar cells (DSSCs) based on both artificial and natural dyes was carried out by a fine synthesis work embedding gold nanoparticles in a TiO(2) semiconductor and perfecting the TiO(2) particle sizes of the scattering layer. Noble metal nanostructures are known for the surface plasmon resonance peculiarity that reveals unique properties and has been implemented in several fields such as sensing, photocatalysis, optical antennas and PV devices. By embedding gold nanoparticles in the mesoporous TiO(2) layer and adding a scattering layer, we were able to boost the power conversion efficiency (PCE) to 10.8%, using an organic ruthenium complex. The same implementation was carried out using a natural dye, betalains, extracted from Sicilian prickly pear. In this case, the conversion efficiency doubled from 1 to 2% (measured at 1 SUN illumination, 100 mW/cm(2) under solar simulation irradiation). Moreover, we obtained (measured at 0.1 SUN, 10 mW/cm(2) under blue light LED irradiation) a record efficiency of 15% with the betalain-based dye, paving the way for indoor applications in organic natural devices. Finally, an attempt to scale up the system is shown, and a betalain-based- dye-sensitized solar module (DSSM), with an active area of 43.2 cm(2) and a PCE of 1.02%, was fabricated for the first time

Fabrication and Morphological Characterization of High-Efficiency Blade-Coated Perovskite Solar Modules.

Organo-metal halide perovskite demonstrates a large potential for achieving highly efficient photovoltaic devices. The scaling-up process represents one of the major challenges to exploit this technology at the industrial level. Here, the scaling-up of perovskite solar modules from 5 × 5 to 10 × 10 cm2 substrate area is reported by blade coating both the CH3NH3PbI3 perovskite and spiro-OMeTAD layers. The sequential deposition approach is used in which both lead iodide (PbI2) deposition and the conversion step are optimized by using additives. The PbI2 solution is modified by adding methylammonium iodide (MAI) which improves perovskite crystallinity and pore filling of the mesoporous TiO2 scaffold. Optimization of the conversion step is achieved by adding a small concentration of water into the MAI-based solution, producing large cubic CH3NH3PbI3 grains. The combination of the two modifications leads to a power conversion efficiency of 14.7% on a perovskite solar module with an active area of 47 cm2

Unveiling the Chemical Composition of Halide Perovskite Films Using Multivariate Statistical Analyses

The local chemical composition of halide perovskites is a crucial factor in determining their macroscopic properties and their stability. While the combination of scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDX) is a powerful and widely used tool for accessing such information, electron-beam-induced damage and complex formulation of the films make this investigation challenging. Here we demonstrate how multivariate analysis, including statistical routines derived from “big data” research, such as principal component analysis (PCA), can be used to dramatically improve the signal recovery from fragile materials. We also show how a similar decomposition algorithm (non-negative matrix factorisation (NMF)) can unravel elemental composition at the nanoscale in perovskite films, highlighting the presence of segregated species and identifying the local stoichiometry at the nanoscale.S.C., C.D. and G.D. acknowledge funding from ERC under grant number 25961976 PHOTO EM and financial support from the EU under grant number 77 312483 ESTEEM2. S.C., C.D. and G.D. also thank Dr. Francisco de la Peña and Dr. Pierre Burdet for very helpful discussions regarding Hyperspy and MVA. The CHOSE team gratefully acknowledges the European Union's Horizon 2020 Framework Program for funding Research and Innovation under Grant agreement no. 653296 (CHEOPS). M.A.-J. thanks Nava Technology Limited, Cambridge Materials Limited and EPSRC (grant number: EP/M005143/1) for their funding and technical support. S.D.S. acknowledges support from the Royal Society and Tata Group (UF150033) and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement number 756962)