Advancing perovskite solar cell technologies toward their theoretical power conversion efficiency (PCE) requires delicate control over the carrier dynamics throughout the entire device. By controlling the formation of the perovskite layer and careful choices of other materials, we suppressed carrier recombination in the absorber, facilitated carrier injection into the carrier transport layers, and maintained good carrier extraction at the electrodes. When measured via reverse bias scan, cell PCE is typically boosted to 16.6% on average, with the highest efficiency of ~19.3% in a planar geometry without antireflective coating. The fabrication of our perovskite solar cells was conducted in air and from solution at low temperatures, which should simplify manufacturing of large-area perovskite devices that are inexpensive and perform at high levels.

http://science.sciencemag.org/content/sci/345/6196/542.full.pdf

Interface engineering of highly efficient perovskite solar cells

State-of-the-art photovoltaics use high-purity, large-area, wafer-scale single-crystalline semiconductors grown by sophisticated, high-temperature crystal growth processes. We demonstrate a solution-based hot-casting technique to grow continuous, pinhole-free thin films of organometallic perovskites with millimeter-scale crystalline grains. We fabricated planar solar cells with efficiencies approaching 18%, with little cell-to-cell variability. The devices show hysteresis-free photovoltaic response, which had been a fundamental bottleneck for the stable operation of perovskite devices. Characterization and modeling attribute the improved performance to reduced bulk defects and improved charge carrier mobility in large-grain devices. We anticipate that this technique will lead the field toward synthesis of wafer-scale crystalline perovskites, necessary for the fabrication of high-efficiency solar cells, and will be applicable to several other material systems plagued by polydispersity, defects, and grain boundary recombination in solution-processed thin films.

/pdf/high-efficiency-solution-processed-perovskite-solar-cells-jmd7w75mq9.pdf

High-efficiency solution-processed perovskite solar cells with millimeter-scale grains

Metal-halide perovskites are crystalline materials originally developed out of scientific curiosity. Unexpectedly, solar cells incorporating these perovskites are rapidly emerging as serious contenders to rival the leading photovoltaic technologies. Power conversion efficiencies have jumped from 3% to over 20% in just four years of academic research. Here, we review the rapid progress in perovskite solar cells, as well as their promising use in light-emitting devices. In particular, we describe the broad tunability and fabrication methods of these materials, the current understanding of the operation of state-of-the-art solar cells and we highlight the properties that have delivered light-emitting diodes and lasers. We discuss key thermal and operational stability challenges facing perovskites, and give an outlook of future research avenues that might bring perovskite technology to commercialization.

Metal-halide perovskites for photovoltaic and light-emitting devices

The large photocurrent hysteresis observed in many organometal trihalide perovskite solar cells has become a major hindrance impairing the ultimate performance and stability of these devices, while its origin was unknown. Here we demonstrate the trap states on the surface and grain boundaries of the perovskite materials to be the origin of photocurrent hysteresis and that the fullerene layers deposited on perovskites can effectively passivate these charge trap states and eliminate the notorious photocurrent hysteresis. Fullerenes deposited on the top of the perovskites reduce the trap density by two orders of magnitude and double the power conversion efficiency of CH(3)NH(3)PbI(3) solar cells. The elucidation of the origin of photocurrent hysteresis and its elimination by trap passivation in perovskite solar cells provides important directions for future enhancements to device efficiency.

/pdf/origin-and-elimination-of-photocurrent-hysteresis-by-3c3hhy02s3.pdf

Origin and elimination of photocurrent hysteresis by fullerene passivation in CH3NH3PbI3 planar heterojunction solar cells

Already exhibiting solar to electrical power conversion efficiencies of over 17%, organic–inorganic lead halide perovskite solar cells are one of the most promising emerging contenders in the drive to provide a cheap and clean source of energy One concern however, is the potential toxicology issue of lead, a key component in the archetypical material The most likely substitute is tin, which like lead, is also a group 14 metal While organic–inorganic tin halide perovskites have shown good semiconducting behaviour, the instability of tin in its 2+ oxidation state has thus far proved to be an overwhelming challenge Here, we report the first completely lead-free, CH3NH3SnI3 perovskite solar cell processed on a mesoporous TiO2 scaffold, reaching efficiencies of over 6% under 1 sun illumination Remarkably, we achieve open circuit voltages over 088 V from a material which has a 123 eV band gap

/pdf/lead-free-organic-inorganic-tin-halide-perovskites-for-ex4x3kkzgb.pdf

Lead-free organic–inorganic tin halide perovskites for photovoltaic applications

Organometal halide perovskites have tremendous potential as light absorbers for photovoltaic applications. In this work we demonstrate hybrid solar cells based on the mixed perovskite CH3 NH3 PbI2 Cl in a thin film sandwich structure, with unprecedented reproducibility and generating efficiencies up to 10.8%. The successfulness of our approach is corroborated by the experimental electronic structure determination of this perovskite.

Perovskite-based hybrid solar cells exceeding 10% efficiency with high reproducibility using a thin film sandwich approach.

L.B. and B.C. contributed equally to this work. The authors thank R. Rieke from Rieke Metals for useful suggestions. This work was financially supported by BOF, UHasselt, the Flemish Odysseus program, and the Interreg project Organext. A. H. is a postdoctoral research fellow of the Research Foundation-Flanders (FWO Vlaanderen).

Towards Efficient Hybrid Solar Cells Based on Fully Polymer Infiltrated ZnO Nanorod Arrays

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.

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

This paper focuses on the characterization of the ZnO/poly(3-hexylthiophene) (P3HT) interfaces in nanostructured hybrid solar cells, aiming to elucidate the relationship between thermal treatment, local morphology, and device performance. An equivalent impedimetric model for the device is proposed, allowing us to extract information about the ZnO/P3HT interface morphology and its impact on the photovoltaic properties by comparing devices with and without nanopatterning. It is found that the influence of thermal treatment on performance lies solely in the interface, resulting from a different interfacial morphology of P3HT depending on which crystal direction of ZnO is present.

Influence of Interface Morphology onto the Photovoltaic Properties of Nanopatterned ZnO/Poly(3-hexylthiophene) Hybrid Solar Cells. An Impedance Spectroscopy Study

Hybrid solar cells based on the mixed metal halide perovskite absorber MeNH3PbI2Cl, sandwiched between selective contacts of TiO2 and poly-3-hexylthiophene show unprecedented reproducibility with efficiencies up to 10.8%.

Linny Baeten

Papers

Perovskite-based hybrid solar cells exceeding 10% efficiency with high reproducibility using a thin film sandwich approach.

Towards Efficient Hybrid Solar Cells Based on Fully Polymer Infiltrated ZnO Nanorod Arrays

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

Influence of Interface Morphology onto the Photovoltaic Properties of Nanopatterned ZnO/Poly(3-hexylthiophene) Hybrid Solar Cells. An Impedance Spectroscopy Study

Perovskite‐Based Hybrid Solar Cells Exceeding 10% Efficiency with High Reproducibility Using a Thin Film Sandwich Approach.