Detection of gamma photons using solution-grown single crystals of hybrid lead halide perovskites Sergii Yakunin, 1, 2 Dmitry N. Dirin, 1, 2 Yevhen Shynkarenko 1,3, Viktoriia Morad, 1 Ihor Cherniukh, 1 Olga Nazarenko, 1,2 Dominik Kreil, 1 Thomas Nauser, 4 and Maksym V. Kovalenko *1,2 1 Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland 2 Laboratory for Thin Films and Photovoltaics, Empa Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland 3 Department of Photonic Processes, Institute of Physics, National Academy of Sciences of Ukraine, 46 Prospekt Nauky, Kyiv 03680, Ukraine 4 Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland * E-mail: mvkovalenko@ethz.ch NATURE PHOTONICS www.nature.com/naturephotonics 1
Supplementary Note 1. Calculation of the sensitivity of a MAPbI 3 SC to soft X-rays in a photoconductive mode of operation. The X-ray photon flux, F, onto the MAPbI 3 SC was measured to be 6 10 7 cm -2 s -1. The ionizing radiation dose in a single crystal (SC) of MAPbI 3 was then calculated as: DD =!!!!!.!"!!!"!! 2.9!"#!"!! (S1), where ρ is the specific density of the SC of MAPbI 3, E ph is the X-ray photon energy (8 kev for Cu Kα soft X-rays) and l is the penetration depth, i.e., the depth up to which the quantity 1-e -1 (63%) of X-ray photons with an energy of 8 kev is absorbed. In air, the ionizing radiation dose would be ~6.9 times smaller than inside a SC of MAPbI 3 due to the lower X-ray photon absorption of air: DD!"# 0.42!"#!"#!"!! (S2). The sensitivity, G, of a SC of MAPbI 3 with an irradiated area, S, of 8 mm 2 with a photocurrent, ΔI, of 22 na is: GG =!" 0.65!! (S3),!!"#!!"!!!"#!"#!"! and the corresponding specific sensitivity, taking into account the absorption depth of 30 µm, is ~220 µc mgy air 1 cm -3. 2 NATURE PHOTONICS www.nature.com/naturephotonics
SUPPLEMENTARY INFORMATION Supplementary Note 2. Evaluation of the efficiency of photons-to-carriers conversion in a photoconductive mode of operation. For the evaluation of the efficiency of photons-to-carriers conversion, we measured the activity, A, of a 11 C source to be 70 GBq. This permitted the estimation of the photon flux in a solid angle of the detector of area, S, of 12 mm 2 displaced at a distance, R, of 10 cm from the source. We took into account that the decay of 11 C produces two photons with the energy, E ph1, of 0.511 MeV from electron-positron annihilation and one gamma photon with the energy, E ph2, of 0.98 MeV. We also include different penetration (absorption) depths for these photon energies in MAPbI 3 SC: l 1 =22 mm and l 2 =55 mm, respectively, for 0.511 MeV and 0.98 MeV photons. From the value of the photocurrent (ΔI) of 5 na produced by a detector with a thickness, d, of 2 mm we evaluated the photon energy efficiency, η, as (where W is the charge pair creation energy): ηη =!!!!!!"!!!!!!!!!!!!!!!!!!!!!!!!!!! 19% (S4), This takes into account only one type of charge carrier, owing to the fact that the mobilities of holes in MAPbI 3 SCs are notably larger (4-6 times) than that of electrons (see Ref. 5 of the Main Text). The gamma photon to charge carrier generation efficiency (charge carriers per absorbed gamma photon) is estimated as: ηη!!!!!!!!!!!! 2.5 10! (S5). NATURE PHOTONICS www.nature.com/naturephotonics 3
Supplementary Figure 1. Measurement of the decay time after a gamma pulse shows the applicability of a computer soundcard as a multichannel analyser. The relaxation time of ~100 µs is suitable for acquisition by a PC sound card with a discretization frequency of 144 khz. 4 NATURE PHOTONICS www.nature.com/naturephotonics
SUPPLEMENTARY INFORMATION Supplementary Figure 2. A two-pixel gamma detector constructed on a single iodine-treated MAPbBr 3 SC. Such a choice of a crystal stems from the convenient rectangular shape of MAPbBr 3 SCs, whereas I-treatment is needed for improving the sensitivity to gamma-photons. (a) Bipolar signal pulses from the signal electrode. (b) Counting profiles recorded simultaneously for each pixel as a function of source displacement ( 137 Cs source activity A=2.2 MBq, displacement speed 0.1 mm/s). The inset shows a schematic of the detector and the locations of the three electrodes (one signal and two bias electrodes). NATURE PHOTONICS www.nature.com/naturephotonics 5
Supplementary Figure 3. Energy-resolved spectrum of 241 Am recorded with CdZnTe SC. 6 NATURE PHOTONICS www.nature.com/naturephotonics
SUPPLEMENTARY INFORMATION Supplementary Figure 4. Energy resolved spectra of an 241 Am source recorded by an I-treated MAPbBr 3 SC cooled with dry ice to ~220 K. It should be noted that the increase of bias from 100 to 140 V shifts the photo-peak to higher MCA channels, illustrating that charge-collection efficiency remains a strongly limiting factor. Also the µτ product of I-treated MAPbBr 3 SCs is lower than that of MAPbI 3 SCs by a factor of 3. These observations clearly demonstrate that compositional engineering of lead halide perovskites for improving the spectral resolution should concentrate on minimizing the ionic drift, while maximizing the µτ product. NATURE PHOTONICS www.nature.com/naturephotonics 7