Wenjun Chen, Seungbae Ahn, C. Ingrosso, A. Panniello, M. Striccoli, G. Bianco, A. Agostiano, G. Bruno, M. Curri, O. Vázquez-Mena
Quantum dots (QDs) have extraordinary strong light absorption and size tunable bandgap. However, QD films are typically limited to ~200-300 nm due to their poor charge mobility. This severely limits the quantum efficiency of QD devices for λ <750 nm (infrared). Herein, we report a record 1 μm thick QD film using intercalated graphene layers as transparent current extractors. This overcomes QD poor mobility, ensuring both effective light absorption and charge extraction towards the near-infrared reaching quantum efficiency (EQE) of 90%. The short diffusion length (LD<200 nm) of QDs limits their useful thickness to ~200-300 nm1–4 , resulting in poor infrared light absorption. To overcome this limitation, we have built a 1 µm thick QD film with intercalated transparent graphene electrodes that keep high charge collection efficiency. As a result, the 1 µm intercalated devices show a superior EQE reaching 90% at λ ~800 nm without the drop of quantum efficiency at λ ~700 nm observed in most QD devices. The EQE of intercalated devices improves over the entire λ~ 600-1100 nm spectrum as the thickness increases from 100 nm to 1 μm, clearly breaking the restriction that the diffusion length of QDs imposes on the film thickness. This improves absorption and charge collection in the infrared.
{"title":"Record 1-micron thick QD film photodetectors using intercalated graphene electrodes for high responsivity in the infrared","authors":"Wenjun Chen, Seungbae Ahn, C. Ingrosso, A. Panniello, M. Striccoli, G. Bianco, A. Agostiano, G. Bruno, M. Curri, O. Vázquez-Mena","doi":"10.1117/12.2569809","DOIUrl":"https://doi.org/10.1117/12.2569809","url":null,"abstract":"Quantum dots (QDs) have extraordinary strong light absorption and size tunable bandgap. However, QD films are typically limited to ~200-300 nm due to their poor charge mobility. This severely limits the quantum efficiency of QD devices for λ <750 nm (infrared). Herein, we report a record 1 μm thick QD film using intercalated graphene layers as transparent current extractors. This overcomes QD poor mobility, ensuring both effective light absorption and charge extraction towards the near-infrared reaching quantum efficiency (EQE) of 90%. The short diffusion length (LD<200 nm) of QDs limits their useful thickness to ~200-300 nm1–4 , resulting in poor infrared light absorption. To overcome this limitation, we have built a 1 µm thick QD film with intercalated transparent graphene electrodes that keep high charge collection efficiency. As a result, the 1 µm intercalated devices show a superior EQE reaching 90% at λ ~800 nm without the drop of quantum efficiency at λ ~700 nm observed in most QD devices. The EQE of intercalated devices improves over the entire λ~ 600-1100 nm spectrum as the thickness increases from 100 nm to 1 μm, clearly breaking the restriction that the diffusion length of QDs imposes on the film thickness. This improves absorption and charge collection in the infrared.","PeriodicalId":145218,"journal":{"name":"Organic Photonics + Electronics","volume":"100 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128328243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yunpeng Qin, Ye Xu, Zhengxing Peng, Jianhui Hou, H. Ade
Thermal transition of OSCs constituent materials are often insufficiently researched, resulting in trial-and-error rather than rational approaches to post-casting processing strategies to improve aggregation to enhance the power conversion efficiency. Despite the potential utility, little is known about the thermal transitions of the high-performance acceptors. Here, by using an optical method, we discover that the acceptor N3 has a clear solid-state aggregation transition at 82 °C. The transition informs and enables a double-annealing method that can fine‐tune aggregation and the device morphology. Compared with 16.6% efficiency for the control devices, higher efficiency of 17.6% is obtained through the improved protocol. Design of high-performance acceptors with yet lower aggregation transitions might be required to successfully transition to low thermal budget industrial processing methods where annealing temperatures on plastic substrates have to be kept low.
{"title":"Low temperature aggregation transitions in N3 and Y6 acceptors enable double-annealing method that yields hierarchical morphology and superior efficiency in nonfullerene organic solar cells","authors":"Yunpeng Qin, Ye Xu, Zhengxing Peng, Jianhui Hou, H. Ade","doi":"10.1117/12.2570507","DOIUrl":"https://doi.org/10.1117/12.2570507","url":null,"abstract":"Thermal transition of OSCs constituent materials are often insufficiently researched, resulting in trial-and-error rather than rational approaches to post-casting processing strategies to improve aggregation to enhance the power conversion efficiency. Despite the potential utility, little is known about the thermal transitions of the high-performance acceptors. Here, by using an optical method, we discover that the acceptor N3 has a clear solid-state aggregation transition at 82 °C. The transition informs and enables a double-annealing method that can fine‐tune aggregation and the device morphology. Compared with 16.6% efficiency for the control devices, higher efficiency of 17.6% is obtained through the improved protocol. Design of high-performance acceptors with yet lower aggregation transitions might be required to successfully transition to low thermal budget industrial processing methods where annealing temperatures on plastic substrates have to be kept low.","PeriodicalId":145218,"journal":{"name":"Organic Photonics + Electronics","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129562291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Hodges, Luis Valerio Frias, Á. De La Rosa, Alma Ileana Leyva, X. Tong
The methylammonium lead iodide CH3NH3PbI3 (MAPbI3) perovskites have attracted a lot of attention as a possible absorber material for thin film solar cells due to their bandgap energy, high optical absorption coefficients and low-cost solution-processing deposition approaches. MAPbI3 perovskite solar cells have evolved with transformative potential with laboratory efficiencies greater than 20%. Perovskite absorber materials are very inexpensive to synthesize and simple to manufacture, making them an extremely commercially viable option. Perovskites of compositional variations ABX3 can yield a range of crystal structures, phases and stabilities. The Goldschmidt’s Tolerance Factor is a reliable figure of merit or empirical index to forecast the formation of preferred and stable structures and phases with ABX3 mixed halide perovskite tolerance factors in the range of 0.9 to 1. Here, we probe perovskites of compositional variations ABX3 with tolerance factors in the range of 0.9 to 1.0, and a large effective ionic radius greater than 200 pm. We report on the structural and optical properties of these perovskites. Photovoltaic (PV) devices were fabricated using these high tolerance factor perovskites. We report we have achieved power conversion efficiencies (PCEs) greater than 21% using the high tolerance factor perovskites investigated. The high tolerance perovskites were also characterized using synchrotron X-ray absorption near edge structure (XANES) spectroscopy at the National Synchrotron Light Source (NSLS) II at Brookhaven National Laboratory (BNL). XANES was used to probe the electronic structure of the high tolerance factor perovskites investigated.
{"title":"Synchrotron and optical probing of mixed lead halide perovskites for photovoltaics","authors":"D. Hodges, Luis Valerio Frias, Á. De La Rosa, Alma Ileana Leyva, X. Tong","doi":"10.1117/12.2569674","DOIUrl":"https://doi.org/10.1117/12.2569674","url":null,"abstract":"The methylammonium lead iodide CH3NH3PbI3 (MAPbI3) perovskites have attracted a lot of attention as a possible absorber material for thin film solar cells due to their bandgap energy, high optical absorption coefficients and low-cost solution-processing deposition approaches. MAPbI3 perovskite solar cells have evolved with transformative potential with laboratory efficiencies greater than 20%. Perovskite absorber materials are very inexpensive to synthesize and simple to manufacture, making them an extremely commercially viable option. Perovskites of compositional variations ABX3 can yield a range of crystal structures, phases and stabilities. The Goldschmidt’s Tolerance Factor is a reliable figure of merit or empirical index to forecast the formation of preferred and stable structures and phases with ABX3 mixed halide perovskite tolerance factors in the range of 0.9 to 1. Here, we probe perovskites of compositional variations ABX3 with tolerance factors in the range of 0.9 to 1.0, and a large effective ionic radius greater than 200 pm. We report on the structural and optical properties of these perovskites. Photovoltaic (PV) devices were fabricated using these high tolerance factor perovskites. We report we have achieved power conversion efficiencies (PCEs) greater than 21% using the high tolerance factor perovskites investigated. The high tolerance perovskites were also characterized using synchrotron X-ray absorption near edge structure (XANES) spectroscopy at the National Synchrotron Light Source (NSLS) II at Brookhaven National Laboratory (BNL). XANES was used to probe the electronic structure of the high tolerance factor perovskites investigated.","PeriodicalId":145218,"journal":{"name":"Organic Photonics + Electronics","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125439957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kyosun Ku, Seiya Kimura, Kyoko Yuasa, K. Hisano, O. Tsutsumi
In chiral-liquid-crystal (LC*) phased, LC molecules are aligned helically; hence, the refractive indices of the LC* materials are altered periodically along the helical axis. The LC* materials have unique optical properties, such as selective reflection, that arise from the periodic structure of the refractive index. The wavelength of the selective reflection depends on the helical pitch as it is a Bragg reflection; therefore, we can control the reflective wavelength by controlling the helical pitch. In this study, we observed the mechano-optical behaviors of LC* elastomers, and discussed the relationship between the chemical structures of elastomers and mechano-responsive optical properties. When tensile strain was applied to the films, reversible hypsochromic shift in the reflection wavelength was induced. The results of the mechano-optical behavior observed for the LC* elastomers suggest that LC* materials have potential for application in mechanical sensors for soft robots.
{"title":"Control of molecular-level mechano-optical response of chiral liquid-crystalline elastomers","authors":"Kyosun Ku, Seiya Kimura, Kyoko Yuasa, K. Hisano, O. Tsutsumi","doi":"10.1117/12.2569098","DOIUrl":"https://doi.org/10.1117/12.2569098","url":null,"abstract":"In chiral-liquid-crystal (LC*) phased, LC molecules are aligned helically; hence, the refractive indices of the LC* materials are altered periodically along the helical axis. The LC* materials have unique optical properties, such as selective reflection, that arise from the periodic structure of the refractive index. The wavelength of the selective reflection depends on the helical pitch as it is a Bragg reflection; therefore, we can control the reflective wavelength by controlling the helical pitch. In this study, we observed the mechano-optical behaviors of LC* elastomers, and discussed the relationship between the chemical structures of elastomers and mechano-responsive optical properties. When tensile strain was applied to the films, reversible hypsochromic shift in the reflection wavelength was induced. The results of the mechano-optical behavior observed for the LC* elastomers suggest that LC* materials have potential for application in mechanical sensors for soft robots.","PeriodicalId":145218,"journal":{"name":"Organic Photonics + Electronics","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123521443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Khorramshahi, Navid Ghazizadeh, I. Kymissis, A. Takshi
The bandgap tunability in methylammonium (MA) lead halide perovskites has motivated us to design a photoresistor array made of MAPbI3, MAPbBr1.5I1.5, and MAPbBr3. To pattern devices on the same substrate, a novel method of laser engraving the substrate was employed. In this method, first, an indium tin oxide (ITO) coated plastic substrate was laser engraved to make microchannels with a width of 50-100 µm. Capillary motion force was used to fill each channel with a different solution containing the perovskite precursors. The current-voltage characteristics of each sensor were studied under dark and light conditions. Light-emitting diodes with different wavelengths were used to study the response of each sensor to monochromic lights. The results are promising toward the fabrication of larger arrays of photosensors which potentially can be used for compact and integrated photospectrometers in lab-on-a-chip devices.
{"title":"Laser engraving method to fabricate iodide and bromide based perovskite photosensors","authors":"F. Khorramshahi, Navid Ghazizadeh, I. Kymissis, A. Takshi","doi":"10.1117/12.2568258","DOIUrl":"https://doi.org/10.1117/12.2568258","url":null,"abstract":"The bandgap tunability in methylammonium (MA) lead halide perovskites has motivated us to design a photoresistor array made of MAPbI3, MAPbBr1.5I1.5, and MAPbBr3. To pattern devices on the same substrate, a novel method of laser engraving the substrate was employed. In this method, first, an indium tin oxide (ITO) coated plastic substrate was laser engraved to make microchannels with a width of 50-100 µm. Capillary motion force was used to fill each channel with a different solution containing the perovskite precursors. The current-voltage characteristics of each sensor were studied under dark and light conditions. Light-emitting diodes with different wavelengths were used to study the response of each sensor to monochromic lights. The results are promising toward the fabrication of larger arrays of photosensors which potentially can be used for compact and integrated photospectrometers in lab-on-a-chip devices.","PeriodicalId":145218,"journal":{"name":"Organic Photonics + Electronics","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133884483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Field-Effect Transistors (FETs) are the key building blocks in a wide range of electronic applications such as sensors and electrical switches. The emergence of Organic Field-Effect Transistors (OFETs) unveiled special features, which have taken the application of FETs into uncharted territories. These unique features include but are not limited to, low- cost processing, lightweight, mechanical flexibility, biocompatibility, broad material availability, etc. Similar to their inorganic counterparts, doping organic semiconductors (OSC) can significantly alter or improve their electrical and optoelectronic properties, resulting in doping induced OFET multi-functionalities. In this study, the impact of multi-doping on the OFET device performance and functionalities has been systematically investigated and evaluated under varying conditions of light, heat, and gate voltages. The experimental results appear to support the proposed hypothesis behind the multi-functionality of the system under study. The present work will provide valuable scientific insights for the advancement of OFET based sensors, switches, and modulators.
{"title":"A polymer composite based organic FET multi-sensing device","authors":"Thomas H. Debesay, Sam S. Sun, M. Bahoura","doi":"10.1117/12.2568269","DOIUrl":"https://doi.org/10.1117/12.2568269","url":null,"abstract":"Field-Effect Transistors (FETs) are the key building blocks in a wide range of electronic applications such as sensors and electrical switches. The emergence of Organic Field-Effect Transistors (OFETs) unveiled special features, which have taken the application of FETs into uncharted territories. These unique features include but are not limited to, low- cost processing, lightweight, mechanical flexibility, biocompatibility, broad material availability, etc. Similar to their inorganic counterparts, doping organic semiconductors (OSC) can significantly alter or improve their electrical and optoelectronic properties, resulting in doping induced OFET multi-functionalities. In this study, the impact of multi-doping on the OFET device performance and functionalities has been systematically investigated and evaluated under varying conditions of light, heat, and gate voltages. The experimental results appear to support the proposed hypothesis behind the multi-functionality of the system under study. The present work will provide valuable scientific insights for the advancement of OFET based sensors, switches, and modulators.","PeriodicalId":145218,"journal":{"name":"Organic Photonics + Electronics","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121223923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Here we report a Vertical Hybrid Field Effect Transistor (VHFET) that shows an improved saturated output characteristics. Up till today the injection limited regime in vertical transistor was realized using an injection barrier as well as a buried semiconductor (SC) under the source contact. Using previous reported simulations and a new fabrication technique we successfully fabricated and characterized a functional device which operates at the injection limited regime without the need of a current limited source injection barrier. The new architecture shows better gate control with 5 ∙ 105 on/off ratio and 240 mV/dec subthreshold swing. Furthermore, we can set design rules for the vertical source contact to enable high performance Vertical Field Effect Transistors (VFET), some of which are applicable to any short-channel transistor.
{"title":"Contact engineering in vertical hybrid field effect transistor","authors":"Gil Sheleg, N. Tessler","doi":"10.1117/12.2570138","DOIUrl":"https://doi.org/10.1117/12.2570138","url":null,"abstract":"Here we report a Vertical Hybrid Field Effect Transistor (VHFET) that shows an improved saturated output characteristics. Up till today the injection limited regime in vertical transistor was realized using an injection barrier as well as a buried semiconductor (SC) under the source contact. Using previous reported simulations and a new fabrication technique we successfully fabricated and characterized a functional device which operates at the injection limited regime without the need of a current limited source injection barrier. The new architecture shows better gate control with 5 ∙ 105 on/off ratio and 240 mV/dec subthreshold swing. Furthermore, we can set design rules for the vertical source contact to enable high performance Vertical Field Effect Transistors (VFET), some of which are applicable to any short-channel transistor.","PeriodicalId":145218,"journal":{"name":"Organic Photonics + Electronics","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131552656","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Highly crystalline organic semiconductor layers patterned from a solution was inkjet printed for the fabrication of TFTs. A novel printing process enabled the micro-scale control of the film formation through the use of precision spatial placement of printed droplets over the device structure. The printing process used temporal and spatial control of the printed droplets to form a crystallization gradient. The gradient, first nucleated over an electrode that defines the TFT structure is used to recrystallize subsequently printed droplets; the initial printed film was then used to recrystallize subsequent printed regions as the channel region is deposited along the channel length. This printed gradient provides a larger grain structure to form within the active region of the TFT. Furthermore, by controlling the fluid dynamics through drying of the printed droplets, the film thickness profiles could be controlled within a specific region where the semiconductor crystallinity was enhanced
{"title":"Formation of highly crystalline organic semiconductor thin films by inkjet printed thickness gradients","authors":"Wontae Park, J. Anthony, W. Wong","doi":"10.1117/12.2568099","DOIUrl":"https://doi.org/10.1117/12.2568099","url":null,"abstract":"Highly crystalline organic semiconductor layers patterned from a solution was inkjet printed for the fabrication of TFTs. A novel printing process enabled the micro-scale control of the film formation through the use of precision spatial placement of printed droplets over the device structure. The printing process used temporal and spatial control of the printed droplets to form a crystallization gradient. The gradient, first nucleated over an electrode that defines the TFT structure is used to recrystallize subsequently printed droplets; the initial printed film was then used to recrystallize subsequent printed regions as the channel region is deposited along the channel length. This printed gradient provides a larger grain structure to form within the active region of the TFT. Furthermore, by controlling the fluid dynamics through drying of the printed droplets, the film thickness profiles could be controlled within a specific region where the semiconductor crystallinity was enhanced","PeriodicalId":145218,"journal":{"name":"Organic Photonics + Electronics","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116032568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the present study, we propose a combined (hybrid) approach of optical manipulation and photochemical reactions for achieving nano-photomechanical motions with small particles. Aa photochemical reactions, we have employed P-type and T-type photochromic reactions of diarylethene (DAE) and pyranoquinazoline (PQ) derivatives, respectively. Single polymer particle containing each of the photochromic compounds was optically trapped in water with a CW visible laser. At this stage, the particle experienced mainly gradient force and was trapped at the focal point of the CW laser. The absorption force was negligible because most of the photochromic molecules in the particle were in the colorless form. UV exposure induced the photoisomerization of the photochromic molecules, resulting in the increase in the number of colored forms. As a result, the absorption force acting on the particle increased and, the position of the particle shifted towards the light propagation direction depending on experimental condition. After turning the UV light off, the particle went back to the original position. The trapped particle thus underwent reciprocal motion synchronizing with the change of photo-response due to the photochromic reactions.
{"title":"Nano-photomechanical motion of small particles induced by switching photon force through photochemical processes","authors":"S. Ito, K. Setoura, H. Miyasaka","doi":"10.1117/12.2569231","DOIUrl":"https://doi.org/10.1117/12.2569231","url":null,"abstract":"In the present study, we propose a combined (hybrid) approach of optical manipulation and photochemical reactions for achieving nano-photomechanical motions with small particles. Aa photochemical reactions, we have employed P-type and T-type photochromic reactions of diarylethene (DAE) and pyranoquinazoline (PQ) derivatives, respectively. Single polymer particle containing each of the photochromic compounds was optically trapped in water with a CW visible laser. At this stage, the particle experienced mainly gradient force and was trapped at the focal point of the CW laser. The absorption force was negligible because most of the photochromic molecules in the particle were in the colorless form. UV exposure induced the photoisomerization of the photochromic molecules, resulting in the increase in the number of colored forms. As a result, the absorption force acting on the particle increased and, the position of the particle shifted towards the light propagation direction depending on experimental condition. After turning the UV light off, the particle went back to the original position. The trapped particle thus underwent reciprocal motion synchronizing with the change of photo-response due to the photochromic reactions.","PeriodicalId":145218,"journal":{"name":"Organic Photonics + Electronics","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114843491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Finn Babbe, Eloïse Masquelier, Zhi Zheng, C. Sutter‐Fella
An unsolved problem of mixed halide perovskites is the light induced compositional instability. Under illumination microscopic clusters with a higher iodide content form which act as efficient recombination centers reducing device performance. In photoluminescence measurements this leads to the development of a secondary peak at low energies that increases in intensity and shifts towards lower energies. Different theories for about the origin have been developed but the underlying key mechanisms are still under debate. In the presented study the photoluminescence evolution of MAPb(I1.5Br1.5) perovskites with varying microstructure is investigated at various excitation densities and temperatures. We find a more evolved segregation mechanism with an intermediate stage between the commonly reported mixed phase and the appearance of the I-rich clusters (Br content < 50%). In this intermediate stage perovskite domains with nearly pure iodide content form (Br content < 25%). Using low excitation densities, the interplay between the I-rich domains and the I-rich clusters leads to a blue shift of the conjunct I-rich luminescence peak. At high excitation densities the I-rich domains and the I-rich clusters are clearly distinguishable, due to a stronger PL response of the I-rich domains. With continuous illumination more I-rich cluster form acting as carrier traps and recombination centers. Due to this, the influence of the few I-rich domains on the PL signature decreases leaving only the commonly reported red shift of the I-rich clusters at later stages of the segregation. The formation of the I-rich domains is fully reversible in the dark and occurs also at elevated temperatures. Measurements on sample with varying grain size further indicate an enhanced formation of those I-rich domains on samples with high grain boundary density possibly by a faster halide mobility along them.
{"title":"Multi stage and illumination dependent segregation in MAPb(I,Br)3","authors":"Finn Babbe, Eloïse Masquelier, Zhi Zheng, C. Sutter‐Fella","doi":"10.1117/12.2568995","DOIUrl":"https://doi.org/10.1117/12.2568995","url":null,"abstract":"An unsolved problem of mixed halide perovskites is the light induced compositional instability. Under illumination microscopic clusters with a higher iodide content form which act as efficient recombination centers reducing device performance. In photoluminescence measurements this leads to the development of a secondary peak at low energies that increases in intensity and shifts towards lower energies. Different theories for about the origin have been developed but the underlying key mechanisms are still under debate. In the presented study the photoluminescence evolution of MAPb(I1.5Br1.5) perovskites with varying microstructure is investigated at various excitation densities and temperatures. We find a more evolved segregation mechanism with an intermediate stage between the commonly reported mixed phase and the appearance of the I-rich clusters (Br content < 50%). In this intermediate stage perovskite domains with nearly pure iodide content form (Br content < 25%). Using low excitation densities, the interplay between the I-rich domains and the I-rich clusters leads to a blue shift of the conjunct I-rich luminescence peak. At high excitation densities the I-rich domains and the I-rich clusters are clearly distinguishable, due to a stronger PL response of the I-rich domains. With continuous illumination more I-rich cluster form acting as carrier traps and recombination centers. Due to this, the influence of the few I-rich domains on the PL signature decreases leaving only the commonly reported red shift of the I-rich clusters at later stages of the segregation. The formation of the I-rich domains is fully reversible in the dark and occurs also at elevated temperatures. Measurements on sample with varying grain size further indicate an enhanced formation of those I-rich domains on samples with high grain boundary density possibly by a faster halide mobility along them.","PeriodicalId":145218,"journal":{"name":"Organic Photonics + Electronics","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122783480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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