Conjugated polyelectrolyte hole transport layer for inverted-type perovskite solar cells

Organic-inorganic hybrid perovskite materials offer the potential for realization of low-cost and flexible next-generation solar cells fabricated by low-temperature solution processing. Although efficiencies of perovskite solar cells have dramatically improved up to 19% within the past 5 years, there is still considerable room for further improvement in device efficiency and stability through development of novel materials and device architectures. Here we demonstrate that inverted-type perovskite solar cells with pH-neutral and low-temperature solution-processable conjugated polyelectrolyte as the hole transport layer (instead of acidic PEDOT:PSS) exhibit a device efficiency of over 12% and improved device stability in air. As an alternative to PEDOT: PSS, this work is the first report on the use of an organic hole transport material that enables the formation of uniform perovskite films with complete surface coverage and the demonstration of efficient, stable perovskite/fullerene planar heterojunction solar cellsopen4

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

Lead-Halide Perovskites Meet Donor-Acceptor Charge-Transfer Complexes

peer reviewedLow-dimensional lead halide hybrid perovskites are nowadays in the spotlight because of their improved stability and extensive chemical flexibility compared to their 3D perovskite counterparts, the current challenge being to design functionalized organic cations. Here, we report on the synthesis and full characterization of a perovskite-like hybrid (a perovskitoid) where the 1D lead iodide layout is patterned with a donor–acceptor charge transfer complex (CTC) between pyrene and tetracyanoquinodimethane, with a chemical formula of (C20H17NH3)PbI3·(C12H4N4). By combining multiple structural analysis and spectroscopic techniques with ab initio modeling, we show that the electronic, optical, and charge-transport properties of the hybrid materials are dominated by the organic CTC, with the inorganic backbone primarily acting as a template for the organization of the donor and acceptor molecules. Interestingly, time-resolved microwave conductivity (TRMC) measurements show an enhanced photocurrent generation in the 1D hybrid compared to the pure organic charge-transfer salt, likely associated with transient localization of the holes on the lead-iodide octahedra. This observation is in line with the close energy resonance between the valence crystal orbitals of the lead-iodide lattice and the frontier occupied molecular orbitals of pyrene predicted by the DFT calculations. Therefore, it paves the way toward the design of new hybrid low-dimensionality perovskites offering a synergic combination of organic and inorganic functionalities

An easy-to-fabricate low-temperature TiO₂ electron collection layer for high efficiency planar heterojunction perovskite solar cells

Organometal trihalide perovskite solar cells arguably represent the most auspicious new photovoltaic technology so far, as they possess an astonishing combination of properties. The impressive and brisk advances achieved so far bring forth highly efficient and solution processable solar cells, holding great promise to grow into a mature technology that is ready to be embedded on a large scale. However, the vast majority of state-of-the-art perovskite solar cells contains a dense TiO2 electron collection layer that requires a high temperature treatment (>450 °C), which obstructs the road towards roll-to-roll processing on flexible foils that can withstand no more than ∼150 °C. Furthermore, this high temperature treatment leads to an overall increased energy payback time and cumulative energy demand for this emerging photovoltaic technology. Here we present the implementation of an alternative TiO2 layer formed from an easily prepared nanoparticle dispersion, with annealing needs well within reach of roll-to-roll processing, making this technology also appealing from the energy payback aspect. Chemical and morphological analysis allows to understand and optimize the processing conditions of the TiO2 layer, finally resulting in a maximum obtained efficiency of 13.6% for a planar heterojunction solar cell within an ITO/TiO2/CH3NH3PbI3-xClxpoly(3-hexylthiophene)/Ag architecture

Generalized approach to the description of recombination kinetics in bulk heterojunction solar cells-extending from fully organic to hybrid solar cells

Lately, research efforts in photovoltaics towards hybrid solar cells based on nanostructured metal oxides and conjugated polymers have been intensifying. However, very limited effort has been spent so far to investigate their recombination kinetics in comparison with their fully organic counterpart. In this work, impedance spectroscopy under different illumination intensities is used to probe the recombination kinetics of hybrid solar cells based on ZnO nanorod arrays and poly(3-hexylthiophene). A recombination-based model developed for fully organic solar cells is effectively applied in our hybrid solar cells, demonstrating their similarity in device physics and establishing the nanorod array/polymer compound as true bulk heterojunction. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4714902