Channel Length Determines the Output Performance of Planar-type Photodetectors Based on MAPbBr3 Perovskite Single Crystals
Stevan Gavranovic a, Jan Pospisil a, Oldrich Zmeskal a, Vitezslav Novak b, Petr Vanysek b, Klara Castkova c, Jaroslav Cihlar c, Martin Weiter a
a Materials Research Centre, Brno University of Technology, Purkynova 464/118, Brno, 61200, Czech Republic
b Brno University of Technology
c CEITEC – Central European Institute of Technology, Brno University of Technology, Purkynova 123, Brno, 61200, Czech Republic
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Poster, Stevan Gavranovic, 215
Publication date: 20th April 2022

We studied the effect of channel length on the output performance and stability of planar-type photodetectors based on high-quality methylammonium lead bromide (MAPbBr3) single crystals. Such crystals, as large as 4.5×4.5×1.2 mm3 were synthesized via inverse temperature crystallization method and were further used for fabrication of planar Au/MAPbBr3/Au photodetectors with variable channel length (in the range between 125 μm and 25 μm). Our findings point out that, the channel length has a profound impact on photocurrent densities and key detector parameters (responsivity R, external quantum efficiency EQE and specific detectivity D*). In the studied five-fold electrode spacing, the photocurrent density increased over four-times, with decreasing active area of the devices. This effect is attributed to intrinsic photocurrent amplification. The responsivity and external quantum efficiency also increase with decreasing active area of the device. Nevertheless, D* increases with increasing channel length. Increasing channel length significantly reduces intensity of the dark current, i.e. noise, which results in higher detectivity of the device. 

Based on the calculated output parameters we determined the champion sample, Au/MaPbBr3/Au photodetector with channel length of 50 µm. This sample exhibited maximum output performance (R of 19.55 A W–1, EQE of 4 253 % and D* of 3.42×1012 cm Hz1/2 W–1) at 200 nW cm–2 which is, to our best knowledge, the weakest light intensity detected using bulk MAPbBr3 single crystals. Moreover, the functional stability of this device showed minimal reduction of photodetection ability after 2 000 cycles, which makes it very promising for the next generation of optoelectronic devices. Our results indicate that the MAPbBr3 single crystals have tremendous potential in the field of filter-free detection of VIS light around 570 nm. In addition, we proved that the sample with channel length of 50 μm shows the best output performances of all as-prepared photodetectors.

S.G. acknowledges the financial support from JCMM Brno Ph.D. Talent. J.P. acknowledges the financial support from GACR junior project No. 20-29499Y.  V.N., P.V., K.C., J.C., and M.W. acknowledge the financial support from GACR project No. 19-23718S.

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