Preparation And Device Performance Of Si-Based Perovskite Quantum Dots Heterojunction Light-Emitting Diodes

Light-emitting diodes(LEDs)based on perovskite have potential application in large-scale display and illumination fields,because of the high brightness,adjustable color,low energy consumption and easy to realize large-area preparation.With the development of research,multi-functional,small and convenient,integrated and low power consumption trends are the future development trend.Si is a dominant material in today's microelectronic industry because of the mature Si-based technology and platform.Combining the Si platform with the perovskite materials can help to fabricate multiple functioning devices in a compact and lightweight format.On the other hand,it can open a way to realize the large area optoelectronic integration and expand their application fields.Therefore,it is an interesting research topic that combining inorganic perovskite quantum dots(QDs)with Si materials.However,undoped single crystal silicon does not match the energy level of the perovskite QDs which induces the low injection efficiency and low luminous efficiency the device.In this work,we present a novel light-emitting diodes containing inorganic n-type CsPbX3 QDs and p-type Si and the devices can emit green light and red light at room temperature;We enhanced the luminescence intensity of the devices by energy band regulation and plasmon resonance effect of Au nanostructure,respectively;We studied the luminescence and electrical properties of the devices under the sine pulsed bias and square pulsed bias driving modes,and direct current(DC)driving mode systematically.It provides a possibility for the practical application of silicon-based perovskite LEDs.1.We present a novel all inorganic perovskite quantum dots(IPQDs)light-emitting diodes containing inorganic n-type CsPbX3 QDs/p-type Si heterojunction.The device structure is ITO/ZnO/CsPbX3/p-Si/Al.Both the 512 nm green and the 683 nm red light emission are achieved at room temperature.The output power density is 0.14 mW/cm2 for green light device and 0.25 mW/cm2 for the red one.The relatively low turn on voltage and high emission intensity in red light device can be attributed to the smaller hole injection barrier between CsPbl3 quantum dots and p-Si.The emission drop off at high current density is observed under DC driving mode,which is signifcantly improved by applying alternating current(AC)square pulses.The enhanced electroluminescence and the improved operation stability at high current density under AC driving mode can be attributed to the less thermal degradation and the reduced charge accumulation in the interface defect states due to the alternated biases.The results demonstrate the possibility of integrating the perovskite QDs with Si platform,which will be helpful to extend their actual applications?2.The poor energy band alignment between the IPQDs and Si limits the device performance,such as the emitting effciency.Here,a light-emitting diode structure is proposed by inserting a Poly-TPD layer between the n-type IPQDs and the p-type Si substrate,a multilayered structure of ITO/ZnO/CsPbX3/Poly-TPD/p-Si/Al is created.The Poly-TPD layer act as hole transporting layer as well as the electron blocking layer for carrier injection balance.The light-emitting diode based on CsPbl3 QDs reaches an output power density of 1.68 mW/cm2 with extewrnal quantum efficiency of 0.91%,which is enhanced by 34-fold compared with the reference device.The CsPbl3 QDs LEDs with 4 mg/ml Poly-TPD could operate for 60 min with an emission decay to the original 4.4%and the stability of the device is obviously improved.Similar emission enhancement is also observed in the device based on CsPbBr3 QDs but the output power density is only 0.6 mW/cm2.The results demonstrate that high-effciency and stable Si-based perovskite LEDs can be realized by rational optical and electronic design.3.In order to further improve the emission intensity of CsPbX3 QDs LEDs,We synthesized Au nanoparticles(Au NPs)with a diameter of about 20 nm and Au nanorods(Au NRs)with a size of 20(±2)nm ×40(±5)nm.Au NPs amd Au NRs are introduced into the hole injection layer,a LED with multilayered structure of ITO/ZnO/CsPbX3/Poly-TPD/Au/p-Si/Al is created.Then,we study the effect of local surface plasmon resonance on the performance of perovskite LED.The resonance peak of Au nanoparticles is around 521 nm,which matched well with the photoluminescence peak of CsPbBr3 QDs.We introduce Au nanoparticles into the hole injection layer,a 2.1 times enhancement of integral EL intensity is obtained and the output power density of CsPbBr3 QDs-based device is increased to 1.2 mW cm-2,which can be attributed to the localized surface plasmon resonance effect between Au NPs and CsPbBr3 excitons.Au nanorods have two resonance peaks at 526 nm and 695 nm,which match well with the photoluminescence emission peaks of CsPbBr3 QDs and CsPbI3 QDs,respectively.After introducing the Au NRs into the hole transport layer,the EL intensity of CsPbBr3 QDs and CsPbI3 QDs LEDs were all improved due to the presence of localized surface plasmon resonance(LSPR)coupling.4.The power consumption and brightness have always been an issue for perovskite light-emitting diodes(PeLED).Here,we improved the luminescence intensity and decreased the current density of the PeLED based on CsPbI3 QDs and p-type Si substrate through an alternating current driving mode.For the different driving voltage modes(under a sine pulsed bias or square pulsed bias),a frequency-dependent electroluminescent(EL)behavior was observed.The devices under a square pulsed bias present a stronger EL intensity under the same voltage due to less thermal degradation at the interface.The red PeLED under a square pulsed bias driving demonstrate that the EL intensity drop-off phenomenon was further improved,and the integrated EL intensity shows the almost linear increase with the increasing driving voltage above 8.5 V.Additionally,compared to the DC driving mode,the red PeLED under the AC condition exhibit higher operating stability due to the reduced charge accumulation in the interface defact states.Our work provides an effective approach for obtaining strong brightness,low power consumption,and high stability light-emitting diodes.