Abstract
We report smart color-sensing devices of two-dimensional lead halide perovskites that exhibit a graded band gap across the film. We observe that the device short-circuit photocurrent is strongly dependent on excitation wavelength λ, and this arises through photoabsorption at different depths in the sample due to the graded bandgaps present. This λ signature in the response of the device is observed in case of steady-state excitation when incident from the high bandgap side of the film, where a complete reversal in the polarity of the photocurrent Iph(t) is obtained as the excitation wavelength is spanned across the visible spectrum. The transient photocurrent reveals λ-specific response arrived from a combination of positive and negative Iph(t) components. The uniqueness of Iph(t) as a function of incident λ can be utilized to examine spectral purity without dispersive optical elements. An equivalent circuit model description provides a possible glimpse into the physical sources involved in contributing to these features.
Original language | English |
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Pages (from-to) | 6577-6584 |
Number of pages | 8 |
Journal | Nano Letters |
Volume | 19 |
Issue number | 9 |
DOIs | |
State | Published - Sep 11 2019 |
Externally published | Yes |
Funding
All authors acknowledge support from EPSRC project ‘Strategic University Network to Revolutionize Indian Solar Energy-SUNRISE (EP/P032591/1)’. R.S. acknowledges the Royal Society Newton-Bhabha International Fellowship.
Keywords
- Graded bandgap hybrid organic-inorganic perovskite
- off-cycle response
- optical time division multiplexing
- transient photocurrent