Design Of Filterless Perovskite Narrow-band Photodetectors With High External Quantum Efficiency Based On Charge Collection Narrowing Mechanism

Spectral selective photodetector(narrowband photodetector)is a device that can convert optical signals of specific wavelengths into electrical signals.It is widely used in fields that require spectral discrimination,such as image sensing,machine vision,spectroscopy,etc.In recent years,perovskite narrow-band photodetectors based on the Charge Collection Narrowing(CCN)mechanism have developed rapidly due to their continuous and tunable spectral response in the visible and near-infrared range.However,the perovskite narrow-band photodetectors that have been proposed based on the CCN mechanism all have the problems of low external quantum efficiency and unsatisfactory narrow-band effect.In order to solve the above-mentioned problems,the following two aspects are mainly done:(1)A new method that uses the barrier effect between the electron blocking/hole transport layer and the perovskite absorption layer to assist in the realization of the CCN mechanism is proposed.According to the Fermi energy level and the conduction/valence band relationship,the energy band diagram of the electron blocking/hole transport layer in contact with the perovskite absorption layer is made,and according to the Fermi energy level difference,it is calculated that the height of the barrier between the two is much greater than 0.3e V,which shows that the electron blocking/hole transport layer can block the transport of electrons significantly.This proves the effectiveness of the method for realizing the CCN mechanism theoretically.Based on the new method,a new filterless perovskite narrow-band photodetector based on the CCN mechanism is designed,the perovskite absorption layer is divided into two parts:the perovskite absorption layer-1 and the perovskite absorption layer-2 by the electron blocking/hole transport layer in the device,the perovskite absorption layer-1—electron blocking/hole transport layer—perovskite absorption layer-2 of the three-layer structure realizes the CCN mechanism through its barrier effect.By changing the thickness and doping concentration of the perovskite absorption layer-1 and the perovskite absorption layer-2,a perovskite photodetector with a long wavelength corresponding to a narrow band spectral response window is realized finally.The semiconductor device simulation software Silvaco TCAD is used to model the device structure,and simulate the influence of material's thickness,doping concentration and other parameters as well as applied bias on the photoelectric performance of the device.The simulation results show that the peak external quantum efficiency of the device with optimal performance is as high as 60.78%,the spectral responsivity is as high as0.386A/W,the full width at half maximum is 9nm,and the spectral rejection ratio is as high as139.06 at zero bias voltage,all of which are better than the performance indicators of the existing CCN-based perovskite narrow-band photodetectors.(2)The effect of anti-reflection film on the performance of the proposed filterless perovskite narrow-band photodetector is studied.Based on the filterless perovskite narrow-band photodetector structure of the electron blocking/hole transport layer to assist in the realization of the CCN mechanism with best performance,it is proposed to use anti-reflection film to further increase the transmission and absorption of the device.The effects of six single-layer anti-reflection films Li F,Mg F₂,Al₂O₃,Si O₂,Si C_xand Si N_xon the external quantum efficiency of the device are mainly studied.By calculating the optical path difference between the reflected light beam before and after the light beam passes through the anti-reflection film,the optimal thickness of the anti-reflection film is calculated according to the quarter optical thickness rule.Silvaco TCAD software is used to simulate and compare the influence of anti-reflection film's thickness on the external quantum efficiency of the device,the simulation result is consistent with the theoretical calculation result.And the simulation results show that the 140nm thick Mg F₂film has the most obvious improvement in the external quantum efficiency of the device.Under negative bias of 5V,when the device structure with best performance uses 140nm thick Mg F₂as the anti-reflection film,the peak external quantum efficiency of the device is as high as 71.767%,the spectral responsivity is as high as 0.456A/W,the full width at half maximum is 9nm,the spectral suppression ratio is as high as144.26.