Flexible Inkjet-Printed Triple Cation Perovskite X-ray Detectors.

Flexible direct conversion X-ray detectors enable a variety of novel applications in medicine, industry, and science. Hybrid organic-inorganic perovskite semiconductors containing elements of high atomic number combine an efficient X-ray absorption with excellent charge transport properties. Due to their additional cost-effective and low-temperature processability, perovskite semiconductors represent promising candidates to be used as active materials in flexible X-ray detectors. Inspired by the promising results recently reported on X-ray detectors that are based on either triple cation perovskites or inkjet-printed perovskite quantum dots, we here investigate flexible inkjet-printed triple cation perovskite X-ray detectors. The performance of the detectors is evaluated by the X-ray sensitivity, the dark current, and the X-ray stability. Exposed to 70 kVp X-ray radiation, reproducible and highly competitive X-ray sensitivities of up to 59.9 µC/(Gyaircm2) at low operating voltages of 0.1 V are achieved. Furthermore, a significant dark current reduction is demonstrated in our detectors by replacing spin-coated poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) with sputtered NiOx hole transport layers. Finally, stable operation of a flexible X-ray detector for a cumulative X-ray exposure of 4 Gyair is presented, and the applicability of our devices as X-ray imaging detectors is shown. The results of this study represent a proof of concept toward flexible direct conversion X-ray detectors realized by cost-effective and high-throughput digital inkjet printing.

Coated and Printed Perovskites for Photovoltaic Applications.

Hybrid organic-inorganic metal halide perovskite semiconductors provide opportunities and challenges for the fabrication of low-cost thin-film photovoltaic devices. The opportunities are clear: the power conversion efficiency (PCE) of small-area perovskite photovoltaics has surpassed many established thin-film technologies. However, the large-scale solution-based deposition of perovskite layers introduces challenges. To form perovskite layers, precursor solutions are coated or printed and these must then be crystallized into the perovskite structure. The nucleation and crystal growth must be controlled during film formation and subsequent treatments in order to obtain high-quality, pin-hole-free films over large areas. A great deal of understanding regarding material engineering during the perovskite film formation process has been gained through spin-coating studies. Based on this, significant progress has been made on transferring material engineering strategies to processes capable of scale-up, such as blade coating, spray coating, inkjet printing, screen printing, relief printing, and gravure printing. Here, an overview is provided of the strategies that led to devices deposited by these scalable techniques with PCEs as high as 21%. Finally, the opportunities to fully close the shrinking gap to record spin-coated solar cells and to scale these efficiencies to large areas are highlighted.