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Liquid-Phase Exfoliated GeSe Nanoflakes For Photoelectrochemical-Type Photodetectors

Gabriele Bianca, 1,2 Marilena Isabella Zappia,3,4 Sebastiano Bellani,1,3 Michele Serri,1 Leyla Najafi,1,3 Beatriz Martín-García,1 Reinier Oropesa-Nuñez, 3 Tomáš Hartman, 5 David Sedmidubský,5 Vittorio Pellegrini,1,3ZdeněkSofer,5 Gennaro Chiarello4 and Francesco Bonaccorso 1,3

1 Graphene Labs, Istituto Italiano di Tecnologia, via Morego 30, Genova, Italy, 2 Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Genova, viaDodecaneso 31, Genova, Italy , 3 BeDimensional Spa., via Lungotorrente Secca 3d, Genova, Italy, 4 Department of Physics, University of Calabria, Via P. Bucci cubo

31/C, Rende (CS), Italy, 5 Department of Inorganic Chemistry, University of Chemistry and Technology Prague, Technická 5, Prague 6, Czech Republic

WORKSTATION

Gabriele Bianca

PhD student IIT –Graphene Labs, Genoa (Italy)

gabriele.bianca@iit.it

Conclusion

GeSe-based Electrode Fabrication and Experimental Setup

Airbrush

GeSe nanoflakes

Graphite paper

Hot plate

- Industrially compatible- Scalable- Flexible electrodes

WorkingElectrode

ReferenceElectrode

CounterElectrode

V

A

SPRAY-COATINGDEPOSITION

PEC-WORKSTATION

Liquid Phase Exfoliation Process2

GeSe nanoflakesDispersion Sonication Purification

ω

1stste

p

GeSe bulk

3rd step2nd step

Advantages:• Scalable production of GeSe nanoflakes-based

inks• High-processability through printing techniques

Equipment: • Sonic bath• Centrifuge

Solvent: • 2-propanol (IPA)

The obtained performances are superior to those of several self‐powered and low‐voltage solution‐processed photodetectors, approaching theones of self‐powered commercial UV–Vis photodetectors. Our results open the way towards the use of 2D GeSe in novel PEC systems.

0.5 M H2SO4

1. M.I. Zappia, G. Bianca et al. Adv. Funct. Mater. 2020, 19095722. F. Bonaccorso et al., Adv. Mater., 2016, 28, 6136

Layered monochalcogenides have been predicted as efficient materials for photoelectrochemical (PEC) applications.1 In this work, single-/few-/multi-layer flakes of germanium selenide (GeSe) have been produced by liquid-phase exfoliation of GeSe crystals to develop water splittingsystem and self-powered PEC-type photodetectors. The devices show responsivities up to 0.32 AW-1 at -0.5 Vvs. RHE under 455 nm excitationwavelength in acidic electrolyte (0.5 M H2SO4), in which they also stably operate.

Introduction

Morphological Characterization

0 40 80 120 1600

10

20

Co

un

ts (

%)

Lateral size (nm)

36 nm

0 5 10 15 200

10

20

Counts

(%

)

Thickness (nm)

2.9 nm

100 150 200 250

A2gIn

ten

sity (

a. u

.)

Raman shift (cm-1)

Bulk

Nanoflakes

A1g

B13g

20 40 60 80

Nanoflakes

511

311

400

111

Inte

nsity (

a. u

.)

2q (°)

201

Bulk

Responsiv

ity

(A W

-1)

Photoelectrochemical Characterization of GeSe PEC-type Photodetectors

-0.4 -0.2 0.0 0.2-80

-60

-40

-20

0

455 nm

505 nm

625 nm

100 150 200 250 300 350 400

A1g

GeSe nanoflakes

Fresh GeSe photoelectrodes

Tested GeSe photoelectrodes

B13g A2

g Si

(substrate)

-0.4 0.0 0.4 0.8 1.2 1.6

10-3

10-2

10-1

100

95.5 mA W-1

455 nm

505 nm

625 nm

316.6 mA W-1

-0.4 0.0 0.4 0.8 1.2 1.6

455 nm

505 nm

625 nm

248.3 mA W-1234.5 mA W-1

-0.4 0.0 0.4 0.8 1.2 1.6

301.7 mA W-1

455 nm

505 nm

625 nm

94.9 mA W-1

dark current density:

>50 mA cm-2

Potential (V vs. RHE)

0.5 M H2SO4 1M KCl 1M KOH

No chemical degradation

Curr

ent

density

(mA

cm

-2)

Potential (V vs. RHE)

Layered GeSe

Top-view Side-viewDepending on pH and thickness,GeSe nanoflakes can act asphotocatalysts for hydrogenand oxygen evolution reaction(HER and OER).

25 µm 25 µm 25 µm1 2 3 4 5 6 7

-6

-4

-2

0

-6

-4

-2

00 2 4 6 8 10 12 14

H+/H2

O2/OH-

Ener

gy (

eV)

Number of layers (-)

pH (-)

Raman shift (cm-1)

Inte

nsity

(a.u

.)