Periodic Reporting for period 4 - SOPHY (The role of Softness in the Physics of Defects: Probing Buried Interfaces in Perovskites Optoelectronic Devices)
Reporting period: 2023-03-01 to 2024-02-29
SOPHY wants to probe optoelectronic processes at buried interfaces in devices, at operating conditions. This is a target which has been long pursued in many fields of nanotechnology for the study of multi-junctions devices, which includes solar cells, light-emitting diodes (LEDs), electro-chemical and photo-catalytic devices. However, so far, direct probe has not been fully achieved. Information has been often built on indirect feedback1 obtained from studies employing independent techniques and from simplified model systems or on experimental data collected without the appropriate temporal/spatial resolution. Unfortunately, given the complexity of interfacial processes, such approaches are not immune from misinterpretation.
Semiconducting metal halide perovskites, and devices based on them, is the primary technology under investigation, given its potential to represent the merging point between the efficient inorganic and the chameleonic organic electronics. The presence of various types chemical interactions in such complex ionic solids gives them a characteristic “soft” fluctuating structure, prone to a wide set of defects which span from lattice distortions to the presence of mobile ions. These are sensitive to the devicoperating conditions, thus, the control of structure-properties relationship, especially at interfaces, becomes elusive, and the prediction of device operation, necessary to engineer reliable systemsj
Perovskite based photovoltaic (PV) devices have recently made spectacular progress in terms of device efficiency, however, the reported values still belong to devices electrically unstable as noted in the NRL efficiency chart5. Promising proofs of concept have been realized for LEDs and optically pumped lasers6, with good perspective for electrically pumped ones. On the other hand, field effect transistors are not taking off yet, and the reason behind this is still unknown. Upon thin film polarization and illumination, slow transients and hysteretic effects have been reported with a variety of dynamics which differ in magnitude and time scale, depending both the material processing and on the specific device architecture, indicating that contact interfaces have a considerable effect This implies a lack of predictive design of the device, pivotal in the development of a reliable technology. There is no direct experimental method that measures the band diagram, and carrier and electric field distributions and evolution in a completed diode. Thus, the study of buried interfaces and the electrostatic of an heterojunction based diode, which will eventually determine the device performances, is a difficult task. For perovskite based devices it is even harder.
SOPHY overall objective is the development and exploitation of an experimental approach which will put together the advantages of optical spectroscopy and electronic spectroscopy and microscopy and will challenge their limitations when taken individually. Time-resolved (visible) pump- (UV)push photoelectron (Tr-PPE) spectroscopy set up will be coupled to a photoelectron microscope (PEEM). Here, this system will be developed to reach, within the same experiment, both time and space resolution . It will map in space electronic structures and the related excitations and how they evolve in time over a large timescale (from femtoseconds to microseconds), in order to follow a wide set of cascade phenomena. Such approach, implemented for the first time on diodes’ cross-sections, will provide the possibility of studying the device at different operation conditions, the key to monitor the “real life” transformations related to the defect physical chemistry of metal halide perovskites
The achievemnt of such target will allow the educated design of perovskite based optoelectronic design, boosting the development of a new technological platform for optoelectronics
Semiconducting metal halide perovskites, and devices based on them, is the primary technology under investigation, given its potential to represent the merging point between the efficient inorganic and the chameleonic organic electronics. The presence of various types chemical interactions in such complex ionic solids gives them a characteristic “soft” fluctuating structure, prone to a wide set of defects which span from lattice distortions to the presence of mobile ions. These are sensitive to the devicoperating conditions, thus, the control of structure-properties relationship, especially at interfaces, becomes elusive, and the prediction of device operation, necessary to engineer reliable systemsj
Perovskite based photovoltaic (PV) devices have recently made spectacular progress in terms of device efficiency, however, the reported values still belong to devices electrically unstable as noted in the NRL efficiency chart5. Promising proofs of concept have been realized for LEDs and optically pumped lasers6, with good perspective for electrically pumped ones. On the other hand, field effect transistors are not taking off yet, and the reason behind this is still unknown. Upon thin film polarization and illumination, slow transients and hysteretic effects have been reported with a variety of dynamics which differ in magnitude and time scale, depending both the material processing and on the specific device architecture, indicating that contact interfaces have a considerable effect This implies a lack of predictive design of the device, pivotal in the development of a reliable technology. There is no direct experimental method that measures the band diagram, and carrier and electric field distributions and evolution in a completed diode. Thus, the study of buried interfaces and the electrostatic of an heterojunction based diode, which will eventually determine the device performances, is a difficult task. For perovskite based devices it is even harder.
SOPHY overall objective is the development and exploitation of an experimental approach which will put together the advantages of optical spectroscopy and electronic spectroscopy and microscopy and will challenge their limitations when taken individually. Time-resolved (visible) pump- (UV)push photoelectron (Tr-PPE) spectroscopy set up will be coupled to a photoelectron microscope (PEEM). Here, this system will be developed to reach, within the same experiment, both time and space resolution . It will map in space electronic structures and the related excitations and how they evolve in time over a large timescale (from femtoseconds to microseconds), in order to follow a wide set of cascade phenomena. Such approach, implemented for the first time on diodes’ cross-sections, will provide the possibility of studying the device at different operation conditions, the key to monitor the “real life” transformations related to the defect physical chemistry of metal halide perovskites
The achievemnt of such target will allow the educated design of perovskite based optoelectronic design, boosting the development of a new technological platform for optoelectronics
The main activities were focused on the understanding of the defects physics of metal halide perovskites as a function their chemical composition by exploiting the coupling of UV-visible pump-probe set up to the PEEMto visualize the optoelectronic processes in soft semiconductors and their devices. Here, the relevant achievements are reported:
1) a novel experimental approach to investigate semiconductors and optoelectronic devices photophysics has been developed and validated. It allows to probe, with space and energy resolution, carrier dynamics.
2) we correlate the role of molecular interactions and structural deformations to the presence and nature of defects in 2D and 3D metal halide perovskites and and the optoelectronic properties and mechanisms in the semiconductor
3) we have correlated the chemical nature and photo-chemistry of defect in perovskites with their role on the optoelectronic mechanisms in metal halide perovskites and their devices. In particular we have provided a clear description of how defects define the optoelectronic quality and stability/reliability of the material and device. The knowledge acquired has allowed us to provide technological relevant solution to the development of a novel optoelectronic technology platform.
The output of SOPHY has been disseminated both within the scientific community (conferences, workshop and expedition in relevant reserach Institututions). Importantly, the knowledge developed about defects managements within SOPHY posed the bases for the sucesfull preparation and execution of a ERC POC (FLE-X).
1) a novel experimental approach to investigate semiconductors and optoelectronic devices photophysics has been developed and validated. It allows to probe, with space and energy resolution, carrier dynamics.
2) we correlate the role of molecular interactions and structural deformations to the presence and nature of defects in 2D and 3D metal halide perovskites and and the optoelectronic properties and mechanisms in the semiconductor
3) we have correlated the chemical nature and photo-chemistry of defect in perovskites with their role on the optoelectronic mechanisms in metal halide perovskites and their devices. In particular we have provided a clear description of how defects define the optoelectronic quality and stability/reliability of the material and device. The knowledge acquired has allowed us to provide technological relevant solution to the development of a novel optoelectronic technology platform.
The output of SOPHY has been disseminated both within the scientific community (conferences, workshop and expedition in relevant reserach Institututions). Importantly, the knowledge developed about defects managements within SOPHY posed the bases for the sucesfull preparation and execution of a ERC POC (FLE-X).
The acquired knowledge about defects and defects management in metal halide perovskites, well beyond the state of art in the scientific comunity, is already having an enourmous impact on development and market transition of a powerful technological platform based on perovskite semiconductors. In fact it is allowing an eductaed design of efficient and reliable optoelectronic devices
The development and validation of a novel experimental approach for the investigation of material interfaces and their impact on devices has provided a tool which has been long pursued in many fields of nanotechnology. The exploitation and impact of such powerful tool will not be limited to the field of optoelectronics. The PI expects there will be great resonance in the field of material science, where the correlation between electronic and chemical and structural properties at nanoscale is an open issue, at large. This tool will be a starting point for the development of a new way to approach the investigation of complex chemical and physical systems.
The development and validation of a novel experimental approach for the investigation of material interfaces and their impact on devices has provided a tool which has been long pursued in many fields of nanotechnology. The exploitation and impact of such powerful tool will not be limited to the field of optoelectronics. The PI expects there will be great resonance in the field of material science, where the correlation between electronic and chemical and structural properties at nanoscale is an open issue, at large. This tool will be a starting point for the development of a new way to approach the investigation of complex chemical and physical systems.