Perovskite photovoltaics

Solar cells based on perovskite absorbers are the fastest growing photovoltaic technology in history.  Since their introduction in early 2008 with a starting point power conversion efficiency of ~4%, they have now since left behind amorphous Silicon and are already achieving efficiencies of over 22%, competing with other industry staples such as CIGS and polycrystalline Silicon. Perovskite solar cells have the potential to become a serious contender for the photovoltaic market due to their already demonstrated high device efficiencies, the low-cost of their starting materials and their compatibility with large-scale, solution processing techniques such as roll-to-roll printing on flexible substrates.

In our group, we have focused our research on the development of novel perovskite materials and deposition methods, with a high emphasis on the elucidation of the working principles behind the assembled photovoltaic devices. In particular we focus on the development of novel lead-free perovskites with high stability, and the recycling of lead containing perovskites solar cells. We develop synthetic protocols to prepare highly oriented 2D and 3D perovskite films and study their performance in devices. We also prepared low-cost hole transporting materials and performed in-depth studies on their charge transfer dynamics. As most of these perovskites are very water sensitive we study the stability of the material toward humidity to reveal the degradation process which leads to routes to improve the stability of the perovskite and devices. Additionally we also study the use of perovskite nanocrystals for lighting applications.

Key publications

Yinghong Hu, Johannes Schlipf, Michael Wussler, Michiel L Petrus, Wolfram Jaegermann, Thomas Bein, Peter Muller-Buschbaum, Pablo Docampo, Hybrid Perovskite/Perovskite Heterojunction Solar Cells, ACS Nano, 2016, 10 (6), 5999-6007

We developed a facile solution-based cation infiltration process to deposit layered perovskite (LPK) structures onto methylammonium lead iodide (MAPI) films. Grazing-incidence wide-angle X-ray scattering experiments were performed to gain insights into the crystallite orientation and the formation process of the perovskite bilayer. Our results show that the self-assembly of the LPK layer on top of an intact MAPI layer is accompanied by a reorganization of the perovskite interface. This leads to an enhancement of the open-circuit voltage and power conversion efficiency due to reduced recombination losses, as well as improved moisture stability in the resulting photovoltaic devices.

Andres Binek, Michiel L. Petrus, Niklas Huber, Helen Bristow, Yinghong Hu, Thomas Bein, Pablo Docampo, Recycling perovskite solar cells to avoid lead waste, ACS applied materials & Interfaces, 2016, 8 (20), 12881-12886

Since perovskite solar cells contain toxic lead, a sustainable procedure for handling the cells after their operational lifetime is required. We report a procedure to remove every layer of the solar cells separately, which gives the possibility to selectively isolate the different materials. Besides isolating the toxic lead iodide in high yield, we show that the PbI2 can be reused for the preparation of new solar cells with comparable performance and in this way avoid lead waste. Furthermore, we show that the most expensive part of the solar cell, the conductive glass (FTO), can be reused several times without any reduction in the performance of the devices. With our simple recycling procedure, we address both the risk of contamination and the waste disposal of perovskite based solar cells while further reducing the cost of the system.

Nadja Giesbrecht, Johannes Schlipf, Lukas Oesinghaus, Andreas Binek, Thomas Bein, Peter Muller-Buschbaum, Pablo Docampo, Synthesis of Perfectly Oriented and Micrometer-Sized MAPbBr3 Perovskite Crystals for Thin Film Photovoltaic Applications, ACS Energy Letters, 2016, 1, 150-154

We report a new synthesis approach for the fabrication of bromide-based perovskite planar films based on the control of the deposition environment. We achieve dense layers with large and perfectly oriented crystallites 5–10 μm in size. We additionally correlate photocurrent and perovskite crystal properties in photovoltaic devices and find that this parameter is maximized for ordered systems, with internal quantum efficiencies approaching unity.

Michiel L. Petrus,* Yinghong Hu,* Davide Moia, Philip Calado, Aurelien M.A. Leguy, Piers R.F. Barnes, Pablo Docampo, The Influence of Water Vapor on the Stability and Processing of Hybrid Perovskite Solar Cells Made from Non-Stoichiometric Precursor Mixtures, ChemSusChem, 2016, 9 (18), 2699-2707

The effect of moisture on hybrid methylammonium lead iodide (MAPbI3) perovskite films and solar cells prepared from nonstoichiometric precursor solutions is presented. A small PbI2 excess is found to decelerate moisture-induced degradation compared to stoichiometric samples. Devices containing excess MAI with initially poor efficiencies show a remarkable increase in performance after exposure to moisture owing to a recrystallization process.

  1. L. Petrus, T. Bein, T. J. Dingemans, P. Docampo, A Low Cost Azomethine-Based Hole Transporting Material for Perovskite Photovoltaics”, J. Mater. Chem. A, 2015, 3, 12159

EDOT-OMeTPA was prepared in a simple condensation reaction. When applied to perovskite solar cells, the new hole transporter shows comparable performance to state-of-the-art Spiro-OMeTAD; however the estimated cost contribution is two orders of magnitude lower.