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Photocatalysis Lecture 5 | Monochromatic Photocurrent Conversion Efficiency (IPCE)

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The Incident Monochromatic Photon-Electron Conversion Efficiency (IPCE) is defined as the ratio of the number of electrons flowing through a closed circuit to the number of incident monochromatic photons, used to evaluate the photoconversion efficiency at different wavelengths. It is one of the important indicators for assessing the photoelectrochemical performance of photoelectrodes.

Since semiconductor materials have different responses to incident light of different wavelengths, measuring the IPCE of a photoelectrode can more accurately evaluate the utilization of monochromatic photons by the photoelectrode, and therefore, it can be more targeted in improving the photoelectrode to enhance its photoelectrochemical performance[1].

The IPCE calculation formula is as follows[2]:

Incident Monochromatic Photon-Electron Conversion Efficiency (IPCE) Calculation Formula

jph: Photocurrent density (mA·cm-2), measured by chronoamperometry (constant potential)

h: Planck's constant (6.62×10-34 J·s)

c: Speed of light (3.0×108 m·s-1)

e: Charge carried by a single electron (1.6×10-19 C)

Pmono: Optical power density of monochromatic light (mW·cm-2)

λ: Monochromatic light wavelength

Simplified, it can be represented as formula (2)[1]:

Incident Monochromatic Photon-Electron Conversion Efficiency (IPCE) Calculation Formula

jp: Photocurrent density (mA·cm-2)

jd: Dark current density (mA·cm-2)

λ: Incident monochromatic light wavelength (nm)

pin: Optical power density received by the photoelectrode (mW·cm-2)

The higher the photocurrent density of the photoelectrode, the higher the IPCE value, which can be further improved by enhancing the charge separation and collection efficiency of the photoelectrode material, thereby increasing the IPCE value.

Perfectlight Science and Technology's PL-PES Spectral Photoelectrochemical System can automatically characterize semiconductor materials' photocurrent, photovoltage, and other photoelectric performance parameters as a function of incident light wavelength in the ultraviolet, visible, and near-infrared wavelength range. It can be used in conjunction with Kelvin probes, conductivity probes, and other testing equipment, and can control output light wavelength, light irradiation time, and synchronize with the electrochemical workstation. PL-PES Spectral Photoelectrochemical System is mainly used for photocurrent testing under different applied voltage conditions, different light wavelengths, different light intensities, and different voltage and light intensity scans, as well as open-circuit potential testing under specific light wavelengths.

IPCE Curve and Photocurrent/Voltage Behavior Spectra

Fig.1 a) PL-PES Spectral Photoelectrochemical System; b) IPCE Curve and Photocurrent/Voltage Behavior Spectra

Incident Monochromatic Photon-Electron Conversion Efficiency (IPCE) Calculation

Fig. 2. a) IPCE at 0 V vs. Ag/AgCl[3]; b) IPCE at 1.2 V vs. Ag/AgCl[4]; c) IPCE [5]; d) IPCE at 1.2 VRHE; e) band gaps from photocurrent measurements[6];f) IPCEs at 0.6 and 1.2 VRHE, respectively[7]

References

[1] 张纹. BiVO4-Cu2O串联光电解池催化分解水性能研究[D]. 西安:西北大学. 2021: 9. 

[2] Chen Zhebo, Deutsch Todd G., Jaramillo Thomas F.* et al., Accelerating materials development for photoelectrochemical hydrogen production: Standards for methods, definitions, and reporting protocols[J]. Journal of Materials Research, 2010, 25, 3. 

[3] Kamalesh Debnath, Tanmoy Majumder, Suvra Prakash Mondal*, Highly luminescent nitrogen doped graphene quantum dots sensitized TiO2 nanorod arrays for enhanced photoelectrochemical performance[J]. Journal of Electroanalytical Chemistry, 2022, 909: 116150. 

[4] Zhang Hongwen, Zhang Shuncong*, Long Jinlin*, et al., The Hole-Tunneling Heterojunction of Hematite-Based Photoanodes Accelerates Photosynthetic Reaction[J]. Angew. Chem. Int. Ed. 2021, 60:16009. 

[5] Li Jinglin, Cao Haijie*, Jiao Zhengbo*, et al., The significant role of the chemically bonded interfaces in BiVO4/ZnO heterostructures for photoelectrochemical water splitting[J]. Applied Catalysis B: Environmental, 2021, 285: 119833. 

[6] Gao Ruiting, Su Yiguo*, Wang Lei*, et al. Ultrastable and high-performance seawater-based photoelectrolysis system for solar hydrogen generation[J]. Applied Catalysis B: Environmental, 2022, 304:120883. 

[7] Wang Ying, Liu Deyu*, Kuang Yongbo*, et al., General in situ photoactivation route with IPCE over 80% toward CdS photoanodes for photoelectrochemical applications[J]. Small, 2021, 17: 2104307.

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