Star-shaped triarylamine-based hole-transport materials in perovskite solar cells

Two novel star-shaped triarylamine-based hole transport materials with triphenylamine (STR1), or a partially oxygen-bridged triphenylamine (STR0), as core and para-substituted triphenylamine side arms were synthesized, fully characterized and studied in perovskite solar cells. Their thermal, optical, electrochemical and charge transport properties were examined and compared in the context of their molecular structure. Due to its more planar configuration, STR0 showed a red-shifted absorption in comparison with STR1. STR0 also forms a more stable amorphous glassy state and showed higher glass transition temperature than STR1 and spiro-OMeTAD. These HTMs were tested in perovskite solar cells using a device configuration of FTO/bl-TiO2/mp-TiO2/CH3NH3PbI3/HTM/Au showing a power conversion efficiency of 13.3% for STR0 and 11.5% for STR1. The STR0-based devices showed higher fill factor and better reproducibility than spiro-OMeTAD-based cells. Without dopant additives, solar cells based on STR0 exhibited a good photocurrent density of 16.63 mA cm−2 and the efficiency improved from a starting PCE of 3.9% to 6.6% after two weeks of storage

Identifying Dominant Recombination Mechanisms in Perovskite Solar Cells by Measuring the Transient Ideality Factor

The light ideality factor determined by measuring the open-circuit voltage (V) as a function of light intensity is often used to identify the dominant recombination mechanism in solar cells. Applying this “Suns-V” technique to perovskite cells is problematic since the V evolves with time in a way that depends on the previously applied bias (V), bias light intensity, device architecture and processing route. Here, we show that the dominant recombination mechanism in two structurally similar CH3NH3PbI3 devices containing either mesoporous Al2O3 or TiO2 layers can be identified from the signature of the transient ideality factor following application of a forward bias, V, to the device in the dark. The transient ideality factor is measured by monitoring the evolution of V as a function of time at different light intensities. The initial values of ideality found using this technique are consistent with estimates of the ideality factor obtained from measurements of photoluminescence vs light intensity and electroluminescence vs current density. Time-dependent simulations of the measurement on modeled devices, which include the effects of mobile ionic charge, reveal that this initial value can be correlated to an existing zero-dimensional model while steady-state values must be analyzed taking into account the homogeneity of carrier populations throughout the absorber layer. The analysis shows that Shockley-Read-Hall (SRH) recombination through deep traps at the charge-collection interfaces is dominant in both architectures of measured device. Using transient photovoltage measurements directly following illumination on bifacial devices, we further show that the perovskite–electron-transport-layer interface extends throughout the mesoporous TiO2 layer, consistent with a transient ideality signature corresponding to SRH recombination in the bulk of the film. This method will be useful for identifying performance bottlenecks in alternative variants of perovskite and other mixed ionic-electronic conducting absorber-based solar cells

One-Step Facile Synthesis of a Simple Hole Transport Material for Efficient Perovskite Solar Cells

A study was conducted to report a new, simple, hole transport material (HTM) composed of a central difluorinated phenyl ring, tetra-substituted with paramethoxydiarylamine groups (DFTAB). Devices fabricated using DFTAB demonstrated a stabilized PCE, had a higher energy absorption cutoff than devices utilizing the ubiquitous spiro-OMeTAD, and offered the potential to be used without the addition of ionic additives. The synthesis of DFTAB was carried out in a one pot reaction where 4,4'-dimethoxydiphenylamine was first deprotonated by NaH, followed by nucleophilic aromatic substitution of hexafluorobenzene with in situ generated amide sodium salt. The thermal properties were investigated by thermogravimetric analysis (TGA)

Raw Data for Azetidinium Lead Iodide for Perovskite Solar Cells

Here we prepare azetidinium lead iodide for the first time. Azetidinium lead iodide is a stable, bright orange material which does not appear to form a 3D or a 2D perovskite. It was successfully used as the absorber layer in solar cells. We also show that it is possible to make mixed cation devices by adding the azetidinium cation to methylammonium lead iodide. Mixed azetidinium-methylammonium cells show improved performance and reduced hysteresis compared to methylammonium lead iodide cells. This dataset includes all structural and electrochemical raw data, including thin film XRD, UV/Vis, Cyclic Voltammetry and Mott Schottky measurements. It also includes the main parameters (Efficiency, Open Circuit Voltage, Short Circuit Current Density, Fill Factor) for all those made. The raw data includes JV curve data of the best pixel from each set, a stabilised efficiency measurement for the MAPI, A1 and A2 cell and an EQE measurement of the best overall pixel.For full details of how the data was collected, please see the corresponding paper, available from https://doi.org/10.1039/C7TA07545F

Raw Data for Azetidinium Lead Iodide for Perovskite Solar Cells

Here we prepare azetidinium lead iodide for the first time. Azetidinium lead iodide is a stable, bright orange material which does not appear to form a 3D or a 2D perovskite. It was successfully used as the absorber layer in solar cells. We also show that it is possible to make mixed cation devices by adding the azetidinium cation to methylammonium lead iodide. Mixed azetidinium-methylammonium cells show improved performance and reduced hysteresis compared to methylammonium lead iodide cells. This dataset includes all structural and electrochemical raw data, including thin film XRD, UV/Vis, Cyclic Voltammetry and Mott Schottky measurements. It also includes the main parameters (Efficiency, Open Circuit Voltage, Short Circuit Current Density, Fill Factor) for all those made. The raw data includes JV curve data of the best pixel from each set, a stabilised efficiency measurement for the MAPI, A1 and A2 cell and an EQE measurement of the best overall pixel

Raw Data for Azetidinium Lead Iodide for Perovskite Solar Cells

Here we prepare azetidinium lead iodide for the first time. Azetidinium lead iodide is a stable, bright orange material which does not appear to form a 3D or a 2D perovskite. It was successfully used as the absorber layer in solar cells. We also show that it is possible to make mixed cation devices by adding the azetidinium cation to methylammonium lead iodide. Mixed azetidinium-methylammonium cells show improved performance and reduced hysteresis compared to methylammonium lead iodide cells. This dataset includes all structural and electrochemical raw data, including thin film XRD, UV/Vis, Cyclic Voltammetry and Mott Schottky measurements. It also includes the main parameters (Efficiency, Open Circuit Voltage, Short Circuit Current Density, Fill Factor) for all those made. The raw data includes JV curve data of the best pixel from each set, a stabilised efficiency measurement for the MAPI, A1 and A2 cell and an EQE measurement of the best overall pixel