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Wavelength-Dependent Charge Carrier Dynamics for Single Pixel Color Sensing Using Graded Perovskite Structures
N Ganesh1, Ravichandran Shivanna2, Richard H Friend2
1Chemistry and Physics of Materials Unit , Jawaharlal Nehru Center for Advanced Scientific Research , Jakkur, Bengaluru 560064 , India.
Nano Letters
|August 27, 2019
Summary
We developed novel color-sensing devices using graded band gap perovskite films. These devices show unique photocurrent responses to different light wavelengths, enabling spectral purity analysis.
Area of Science:
- Materials Science
- Optoelectronics
- Solid-State Physics
Background:
- Two-dimensional (2D) lead halide perovskites are promising materials for optoelectronic devices.
- Controlling material properties like band gap is crucial for device functionality.
- Graded band gap structures offer unique optical and electronic properties.
Purpose of the Study:
- To report smart color-sensing devices based on 2D lead halide perovskites with a graded band gap.
- To investigate the wavelength-dependent photocurrent response of these devices.
- To explore the potential of these devices for spectral purity analysis.
Main Methods:
- Fabrication of 2D lead halide perovskite films with a graded band gap.
- Measurement of device short-circuit photocurrent under varying excitation wavelengths (λ).
- Analysis of steady-state and transient photocurrent responses.
- Application of an equivalent circuit model for physical interpretation.
Main Results:
- Device photocurrent strongly depends on excitation wavelength due to depth-dependent photoabsorption.
- A complete reversal in photocurrent polarity is observed across the visible spectrum when light is incident from the high band gap side.
- Transient photocurrent exhibits wavelength-specific components (positive and negative).
Conclusions:
- The unique wavelength-dependent photocurrent signature is a direct result of the graded band gap.
- This phenomenon can be exploited for spectral purity examination without dispersive optical elements.
- An equivalent circuit model provides insights into the underlying physical mechanisms.
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