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Page 4 of 22 Na et al. Soft Sci. 2026, 6, 25

Table 1. Comparison of the zero-power optoelectronic synapses based on different zero-power mechanisms
Minimum Electrical
usable power Mechanical Decay
Mechanism Device structure (type) Wavelength (nm) Ref.
illumination consumption property time (s)
(μW·cm ) (J)
-2
Schottky Au/Bi 2 O 2 Se-V Se /Au (planar) 350/532/1,050 1.2 0 Rigid τ 1 = 0.006, [32]
junction τ 2 = 0.33
(Built-in (532 nm)
potential)
ITO/P3HT/Al (vertical) 445/520/660 20 0 Rigid τ = 10.37 [33]
(520 nm)
Au/P(VDF-TrFE)/ 445 36.6 0 Rigid τ 1 = 0.16, [34]
Cs 2 AgBiBr 6 /ITO (vertical) τ 2 = 3.57
Au/C 8 -BTBT/ 365 158 0 Rigid τ 1 = 0.02, [35]
PEDOT:PSS (planar) τ 2 = 1.8
ITO/Cs 3 Bi 2 Br 9 / 445/520/660 6,000 0 Rigid τ 1 = 0.1, [36]
PMMA/Ag (vertical) τ 2 = 1.5
(445 nm)
Heterojunction In/GaN/BiFeO 3 /Ag (vertical) 325 6.8 0 Rigid τ 1 = 1.52, [37]
(Built-in τ 2 = 35.05
potential)
Au/C 8 -BTBT/F 16 CuPc/Au 365 300 0 Rigid τ 1 = 0.01, [38]
(planar) τ 2 = 1.2
W/WO X /ZnO/ITO (vertical) 350 850 0 Rigid - [39]
ITO/Cs 2 AgBiBr 6 / 445/660 24 (445 nm)/ 0 Rigid τ 1 = 0.07, [40]
P(VDF-TrFE)/pentacene/Au 6,900 τ 2 = 0.45
(vertical) (660 nm) (445 nm)/
τ 1 = 1.26,
τ 2 = 0.37
(660 nm)
ITO/PC 61 BM/ 375/532/808 4.58 (375 nm) 0 Rigid τ 1 = 0.03 ± [41]
MAPbI 3 :Si NCs/ 10 (532 nm) 0.01,
Spiro-OMeTAD/Au (vertical) 1,351 (808 nm) τ 2 = 1.0 ±
0.2 (375
nm)
Ag/InSe/GaN/Ag (planar) 400-780 (Vis)/ 2,200 (Vis)/ 0 Rigid τ 1 = 0.157, [42]
800-1,000 (IR) 9,100 (IR) τ 2 =2.09
(Vis)/
τ 1 = 0.153,
τ 2 = 1.636
(IR)
PTE effect AgNPs-doped ionogel 365/455/530/ 288 (365 nm) 0 Bendable - [43]
(Seebeck heterostructure 590/625/680
effect)
PPy-NPs-doped ionogel 365/455/530/ 144 (365 nm) 0 Bendable/ - [44]
heterostructure 590/625/680/970 stretchable
CNTdoped ionogel 365/455/530/ 144 (365 nm) 0 Stretchable - [45]
heterostructure 590/625/680
Bi 2 O 2 Se-V Se : Bi 2 O 2 Se nanosheet with selenium vacancies; ITO: indium tin oxide; P3HT: poly(3-hexylthiophene-2,5-diyl); P(VDF-TrFE):
poly(vinylidene fluoride-trifluoroethylene); C 8 -BTBT: dioctylbenzothienobenzothiophene; PEDOT:PSS: poly(3,4-ethylenedioxythiophene):
polystyrene sulfonate; PMMA: poly(methyl methacrylate); PC 61 BM: phenyl-C 61 -butyric acid methyl ester; MAPbI 3 : methylammonium lead iodide; Si
NCs: silicon nanocrystals; Spiro-OMeTAD: 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino] -9,9′-spirobifluorene; AgNPs: silver nanoparticles;
PPy-NPs: polypyrrole nanoparticles; CNT: carbon nanotube; Vis: visible; IR: infrared; τ 1 and τ 2 : fast and slow time decay constant from double
exponential fitting, respectively; τ: time decay constant from single exponential fitting.
systematic comparison of the representative zero-power optoelectronic synapses with different zero-power
mechanisms: Schottky junction, heterojunctions, and the PTE effect. The device structure, wavelength,
minimum usable illumination, electrical power consumption, mechanical property, and decay time are
compared for evaluating the suitability of wearable neuromorphic platforms. In this section, we summarize
recent developments in zero-power optoelectronic synapses by categorizing them into these three
representative mechanisms.