Photon recycling in lead iodide perovskite solar cells.

Lead-halide perovskites have emerged as high-performance photovoltaic materials. We mapped the propagation of photogenerated luminescence and charges from a local photoexcitation spot in thin films of lead tri-iodide perovskites. We observed light emission at distances of ≥50 micrometers and found that the peak of the internal photon spectrum red-shifts from 765 to ≥800 nanometers. We used a lateral-contact solar cell with selective electron- and hole-collecting contacts and observed that charge extraction for photoexcitation >50 micrometers away from the contacts arose from repeated recycling between photons and electron-hole pairs. Thus, energy transport is not limited by diffusive charge transport but can occur over long distances through multiple absorption-diffusion-emission events. This process creates high excitation densities within the perovskite layer and allows high open-circuit voltages.The authors acknowledge financial support from the Engineering and Physical Sciences Research Council of the UK (EPSRC) and King Abdulaziz City for Science and Technology (KACST). L.M.P.O. and H.J.B. also thank the Nano doctoral training center (NanoDTC) for financial support. M.S., M.V. and J.M.R. thank the Winton programme for the physics of sustainability. M.C.Q would like to thank the Marie Curie Actions (FP7-PEOPLE-IEF2013) for funding. M.A.J. thanks Nyak Technology Ltd for PhD scholarship and B.E. acknowledges the Foundation for Fundamental Research on Matter (FOM), which is part of the Netherlands Organization for Scientific Research (NWO). F.D. acknowledges funding through a Herchel Smith Research Fellowship. We acknowledge Prof. Henning Sirringhaus, Prof. Neil Greenham, Prof. Ullrich Steiner, Dr. Erwin Reisner and Prof. Richard Phillips for providing support and access to their facilities.This is the author accepted manuscript. The final version is available from the American Association for the Advancement of Science via http://dx.doi.org/10.1126/science.aaf116

MuPix & ATLASpix: Architectures and Results

High Voltage Monolithic Active Pixel Sensors (HV-MAPS) are based ona commercial High Voltage CMOS process and collect charge by driftinside a reversely biased diode. HV-MAPS represent a promising technology for future pixel tracking detectors. Two recent developments are presented. The MuPix has a continuous readout and is being developed for the Mu3e experiment whereas the ATLASPix is being developed for LHC applications with a triggered readout. Both variants have a fully monolithic design including state machines, clock circuitries and serial drivers. Several prototypes and design variants were characterised in the lab and in testbeam campaigns to measure efficiencies, noise, time resolution and radiation tolerance. Results from recent MuPix and ATLASPix prototypes are presented and prospects for future improvements are discussed.High Voltage Monolithic Active Pixel Sensors (HV-MAPS) are based on a commercial High Voltage CMOS process and collect charge by drift inside a reversely biased diode. HV-MAPS represent a promising technology for future pixel tracking detectors. Two recent developments are presented. The MuPix has a continuous readout and is being developed for the Mu3e experiment whereas the ATLASPix is being developed for LHC applications with a triggered readout. Both variants have a fully monolithic design including state machines, clock circuitries and serial drivers. Several prototypes and design variants were characterised in the lab and in testbeam campaigns to measure efficiencies, noise, time resolution and radiation tolerance. Results from recent MuPix and ATLASPix prototypes are presented and prospects for future improvements are discussed