1 Introduction
2 Fabrication methods of perovskite
Fig.2 Solution-based methods of (a) one-step spin coating [25], (b) multiple-step spin coating [26], (c) spray coating [27], (d) slot-die coating [28], (e) blade coating [29], and (f) ink-jet printing [30]. Reprinted with permission from Ref. [25], copyright@2019, Wiley-VCH. Reprinted with permission from Ref. [26], copyright@2020, Elsevier. Reprinted with permission from Ref. [27], copyright@2018, American Chemical Society. Reprinted with permission from Ref. [28], copyright@2019, Elsevier. Reprinted with permission from Ref. [29], copyright@2017, Elsevier. Reprinted with permission from Ref. [30], copyright@2021, Wiley-VCH. |
Fig.3 Vapor-based methods of (a) flash evaporation [31], (b) co-evaporation [32], (c) two-step sequential evaporation [33], (d) multiple-step sequential evaporation [34], and (e) chemical vapor evaporation [35]. Reprinted with permission from Ref. [31], copyright@2017, Royal Society of Chemistry. Reprinted with permission from Ref. [32], copyright@2021, American Chemical Society. Reprinted with permission from Ref. [33], copyright@2021, American Chemical Society. Reprinted with permission from Ref. [34], copyright@2020, Royal Society of Chemistry. Reprinted with permission from Ref. [35], copyright@2017, American Chemical Society. |
2.1 Solution-based methods
2.1.1 Spin coating
2.1.2 Spray coating
2.1.3 Slot-die coating
2.1.4 Blade coating
2.1.5 Ink-jet printing
2.2 Vapor-based methods
2.2.1 Flash evaporation
2.2.2 Co-evaporation
2.2.3 Sequential evaporation
2.2.4 Chemical vapor deposition
2.3 Methods comparison
3 Architectures and performance parameters of photodetectors
3.1 Architectures of photodetectors
3.2 Performance parameters of photodetectors
Tab.1 Comparison between the device structure and performance parameter |
Device structure | EQE | R | Response time | G | LDR | Driving voltage | Photocurrent/dark current | |
---|---|---|---|---|---|---|---|---|
Photodiode | ≤ 100% | Low | High | Short | Small | Large | Low (~0) | Low |
Photoconductor | > 100% | High | Low | Long | Large | Narrow | High | High |
Phototransistor | > 100% | High | Low | Long | Large | Narrow | High | High |
3.2.1 External quantum efficiency
3.2.2 Responsivity
3.2.3 Specific detectivity
3.2.4 On/off ratio
3.2.5 Response time
3.2.6 Linear dynamic range
3.2.7 Gain
3.2.8 Flexibility and stability
4 Processing for flexible photodetectors
4.1 Flexible substrates
4.1.1 Polymer
Tab.2 Properties of typical polymer materials |
Polymer | Light transmittance/% | Dimensional stability | Temperature tolerance/°C | Solvent resistance | Elastic modulus/MPa |
---|---|---|---|---|---|
Polyethylenenaphthalate (PEN) | 87.0 | Well | 120 | Well | 6000 |
Polyethylene terephthalate (PET) | 90.4 | Well | 79 | Well | 4000 |
Polyvinylidene fluoride (PVDF) | 25‒30 | Well | 150 | Well | 1400 |
Polyimide (PI) | 30‒60 | Well | 280 | Well | 500 |
Polydimethylsiloxane (PDMS) | 93 | Fair | 260 | Fair | 150 |
Poly(methyl methacrylimide) (PMMA) | 92 | Fair | 100 | Fair | 6500 |
Fig.6 Perovskite photodetectors on polymer substrates of (a) polyethylenenaphthalate (PEN) [75], (b) polyethylene terephthalate (PET) [76], (c) polyvinylidene fluoride (PVDF) [77], and (d) polyimide (PI) [78]. Reprinted with permission from Ref. [75], copyright@2017, Wiley-VCH. Reprinted with permission from Ref. [76], copyright@2020, American Chemical Society. Reprinted with permission from Ref. [77], copyright@2019, Royal Society of Chemistry. Reprinted with permission from Ref. [78], copyright@2020, American Chemical Society. |
4.1.2 Carbon cloth
4.1.3 Fiber
Fig.8 Fabrication processes and characteristics of (a) yarn [86], (b) metal [87], and (c) polymer fiber-based flexible photodetectors [88]. Reprinted with permission from Ref. [86], copyright@2019, Royal Society of Chemistry. Reprinted with permission from Ref. [87], copyright@2018, Wiley-VCH. Reprinted with permission from Ref. [88], copyright@2022, American Chemical Society. |
4.1.4 Paper
Fig.9 Fabrication process of paper-based flexible: (a) photoconductor [92], (b) photodiode [93], and (c) cubic photodetectors [94]. Reprinted with permission from Ref. [92], copyright@2021, American Chemical Society. Reprinted with permission from Ref. [93], copyright@2021, Elsevier. Reprinted with permission from Ref. [94], copyright@2017, American Chemical Society. |
4.2 Soft electrodes
4.2.1 Metal-based conductive networks
4.2.2 Carbon-based conductive materials
Fig.11 Fabrication processes and device structures of flexible photodetectors with (a) top grapheme electrode [100], (b) bottom grapheme electrode [101], (c) top carbon nanotube electrode [102], and (d) bottom carbon nanotube electrode [103]. Reprinted with permission from Ref. [100], copyright@2021, IOP Publishing. Reprinted with permission from Ref. [101], copyright@2019, American Chemical Society. Reprinted with permission from Ref. [102], copyright@2021, Elsevier. Reprinted with permission from Ref. [103], copyright@2022, Wiley-VCH. |
4.2.3 Two-dimensional conductive materials
4.3 Conformal encapsulation
Fig.13 Flexible photodetectors encapsulated by polymers of (a) polydimethylsiloxane (PDMS) [109] and (b) parylene-C film [110]. PET: polyethylene terephthalate. Reprinted with permission from Ref. [109], copyright@2018, Wiley-VCH. Reprinted with permission from Ref. [110], copyright@2021, Wiley-VCH. |
4.3.1 Single-layer encapsulation
4.3.2 Multilayer stacked encapsulation
4.4 Low-dimensional perovskite-based flexible photodetectors
Fig.15 Flexible photodetectors based on low-dimensional perovskites of (a) nanoparticles [129], (b,c) nanowires [130,131], and (d) nanoflakes [132]. Reprinted with permission from Ref. [129], copyright@2018, Elsevier. Reprinted with permission from Ref. [130], copyright@2019, Wiley-VCH. Reprinted with permission from Ref. [131], copyright@2020, American Chemical Society. Reprinted with permission from Ref. [132], copyright@2017, Royal Society of Chemistry. |
4.5 Elaborate device structures for flexible photodetectors
Fig.16 Flexible photodetectors with (a) assembled polystyrene (PS) bead [138], (b) polymer composite [139], (c) nacre-inspired “brick-and-mortar” [140], and (d) vertebrate-like structures [141]. EVA: ethylene-vinyl acetate, PDMS: polydimethylsiloxane, PMMA: poly(methyl methacrylimide). Reprinted with permission from Ref. [138], copyright@2021, Elsevier. Reprinted with permission from Ref. [139], copyright@2020, Springer Nature. Reprinted with permission from Ref. [140], copyright@2022, Elsevier. Reprinted with permission from Ref. [141], copyright@2020, Springer Nature. |
5 Applications of flexible photodetectors
Tab.3 Performance comparison among non-perovskite-based flexible photodetectors, perovskite-based flexible ones, and perovskite-based rigid ones |
Material | Device properties | Device performances | Ref. | ||||||
---|---|---|---|---|---|---|---|---|---|
Substrate | Waveband | Structure | Responsivity/(A·W‒1) | Detectivity/Jones | LDR/dB | Response time | |||
Sb2Se3 | Flexible | Infrared | Photoconductor | 0.155 | 8.58 × 1010 | ‒ | 35/38 ms | [142] | |
MoS2 | Flexible | Visible | Photoconductor | 540 | ~1 × 1012 | ‒ | 0.5/1.15 s | [143] | |
InSe | Flexible | Visible | Photoconductor | 56 | 1.92 × 1011 | ‒ | ~0.17 s | [144] | |
GaTe | Flexible | Visible | Photoconductor | 240.3 | ‒ | ‒ | 0.4/0.5 s | [145] | |
ZnO | Flexible | Ultraviolet | Photoconductor | 3.24 | 29.6 | ‒ | 17.9/46.6 s | [146] | |
Ga2O3 | Flexible | Ultraviolet | Photovoltaic | 22.75 | 8.2 × 1013 | 97.6 | ‒ | [147] | |
MAPbI3 | Rigid | Visible | Photoconductor | 24.8 | 7.7 × 1012 | ‒ | 4/5.8 ms | [148] | |
MAPbI3 | Flexible | Infrared | Photoconductor | 0.036 | ‒ | ‒ | < 0.1 s | [149] | |
MAPbI3 | Rigid | Infrared | Photovoltaic | 0.14 | 7.37 × 1011 | 192 | 27 ns | [150] | |
MAPbI3 | Flexible | Infrared | Photovoltaic | 0.418 | 1.22 × 1013 | ‒ | ‒ | [151] | |
MAPbBr3 | Rigid | Visible | Photoconductor | > 4000 | > 1 × 1013 | ‒ | ~25 μs | [152] | |
MAPbBr3 | Flexible | Visible | Photoconductor | 5600 | 6.59 × 1011 | ‒ | 3.2/9.2 μs | [75] | |
MAPbBr3 | Rigid | Visible | Photovoltaic | 0.26 | 1.5 × 1013 | 256 | 100 ns | [71] | |
MAPbCl3 | Rigid | Ultraviolet | Photoconductor | 0.07 | > 1 × 1011 | ‒ | 43/37 ms | [153] | |
MAPbCl3 | Rigid | Ultraviolet | Photovoltaic | > 0.15 | ~6 × 1012 | 190 | 15 ns | [154] | |
MAPbCl3 | Flexible | Ultraviolet | Photovoltaic | 0.359 | 7.95 × 1012 | ‒ | 3.91/4.55 ms | [155] | |
CsPbBr3 | Rigid | Visible | Photoconductor | 55 | 9 × 1012 | ‒ | 0.43/0.31 ms | [156] | |
CsPbBr3 | Flexible | Visible | Photoconductor | 31.1 | ‒ | 85 | 16 μs | [81] | |
CsPbBr3 | Rigid | Visible | Photovoltaic | ~10 | 1.88 × 1013 | 172.7 | 28/270 μs | [157] | |
CsPbBr3 | Flexible | Visible | Photovoltaic | 10.1 | 9.35 × 1013 | ‒ | ‒ | [133] | |
CsPbCl3 | Rigid | Ultraviolet | Photoconductor | 2.11 | 5.6 × 1012 | 57 | 77/63 ms | [158] | |
CsPbCl3 | Flexible | Ultraviolet | Photoconductor | > 1 × 106 | 2 × 1013 | ‒ | 0.3/0.35 s | [159] | |
CsPbCl3 | Rigid | Ultraviolet | Photovoltaic | 0.19 | 5.47 × 1012 | ‒ | 4.27/14.9 μs | [160] | |
CsPbCl3 | Flexible | Ultraviolet | Photovoltaic | 0.12 | 1.4 × 1013 | 136 | ~50 μs | [161] | |
Cs2AgBiBr6 | Rigid | Ultraviolet | Photoconductor | 7.01 | 5.66 × 1011 | ‒ | 956/995 μs | [162] | |
Cs2AgBiBr6 | Rigid | Ultraviolet | Photovoltaic | 0.075 | 1.87 × 1012 | 100 | 0.24/0.29 ms | [163] | |
Cs2AgBiBr6 | Flexible | Ultraviolet | Photovoltaic | 0.23 | 1.6 × 1013 | 177.8 | 3.7/3.2 μs | [164] |
5.1 Optical communication
5.2 Image sensing
Fig.18 Schematic diagrams of flexible photodetectors and their application demonstrations in (a) 2D code recognition [178], (b) fingerprint recognition [179], (c) 3D imaging [180], and (d) retina-like imaging [181]. Reprinted with permission from Ref. [178], copyright@2020, Elsevier. Reprinted with permission from Ref. [179], copyright@2021, Springer Nature. Reprinted with permission from Ref. [180], copyright@2021, Wiley-VCH. Reprinted with permission from Ref. [181], copyright@2020, Springer Nature. |
5.3 Health monitoring
Fig.19 Schematic diagrams of flexible photodetectors and their application demonstrations in (a) portable X-ray detecting [182] and (b) ultraviolet irradiation monitoring [155]. Reprinted with permission from Ref. [182], copyright@2022, American Chemical Society. Reprinted with permission from Ref. [155], copyright@2022, Elsevier. |