While there have been many impressive demonstrations of neuromorphic computation in recent years, input stimuli provided to this hardware generally still take a form designed for von Neumann processors. For example, in a CCD detector an array of pixels is sampled at fixed intervals in time. Here we have taken inspiration from the human retina and demonstrated an event-driven sensor which pre-processes optical signals by design. Using a thin film semiconductor as one dielectric layer of a bilayer capacitor, we demonstrate a device which changes its capacitance under illumination. When in series with a resistor, and a constant bias is applied across this device, the voltage dropped across the resistor will spike temporarily as the capacitor (dis)changes, before returning to its equilibrium value. The result is a sensor which spikes in response to changes in illumination, but otherwise outputs zero voltage. This design hence inherently filters out non-pertinent information such as static images, providing a voltage only in response to movement. Using a simple model based on Kirchhoff’s Laws, we are able to parameterize this device and accurately reproduce its behavior in simulations. It is hoped that this work represents the first step towards a paradigm shift for the design of sensing systems for neuromorphic computation, and artificial intelligence in general.
{"title":"Thin film retinomorphic sensors","authors":"J. Labram","doi":"10.1117/12.2593517","DOIUrl":"https://doi.org/10.1117/12.2593517","url":null,"abstract":"While there have been many impressive demonstrations of neuromorphic computation in recent years, input stimuli provided to this hardware generally still take a form designed for von Neumann processors. For example, in a CCD detector an array of pixels is sampled at fixed intervals in time. Here we have taken inspiration from the human retina and demonstrated an event-driven sensor which pre-processes optical signals by design.\u0000\u0000Using a thin film semiconductor as one dielectric layer of a bilayer capacitor, we demonstrate a device which changes its capacitance under illumination. When in series with a resistor, and a constant bias is applied across this device, the voltage dropped across the resistor will spike temporarily as the capacitor (dis)changes, before returning to its equilibrium value. The result is a sensor which spikes in response to changes in illumination, but otherwise outputs zero voltage. This design hence inherently filters out non-pertinent information such as static images, providing a voltage only in response to movement. \u0000\u0000Using a simple model based on Kirchhoff’s Laws, we are able to parameterize this device and accurately reproduce its behavior in simulations.\u0000\u0000It is hoped that this work represents the first step towards a paradigm shift for the design of sensing systems for neuromorphic computation, and artificial intelligence in general.","PeriodicalId":175873,"journal":{"name":"Organic and Hybrid Field-Effect Transistors XX","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120947676","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}
Organic electrochemical transistors (OECTs) have been demonstrated in a wide range of applications such as analyte detection, neural interfacing, impedance sensing and neuromorphic computing. Majority of OECTs use PEDOT:PSS and liquid electrolytes. In this talk, I will discuss the development of biomaterials as solid state electrolytes and conjugated polyelectrolytes (CPEs) as semiconductors for OECTs. The biogels that consist of gelatin and glycerol with high ionic conductivity are used as solid electrolytes. We establish a relation between morphology and protonic-conductivity of the gels, allowing for the fabrication of gel-based OECTs with desirable functionalities, good ON/OFF ratio and transconductance, fast-switching speed, and good stability in ambient air. Anionic CPEs are used as mixed conductor materials for OECTs to replace PEDOT:PSS. CPE-based OECTs operate in the accumulation mode, which allows for much lower energy consumption in comparison to commonly used depletion mode PEDOT:PSS devices. The physical and electrical properties of CPE-K have been fully characterized to allow a direct comparison to other top performing OECT materials. CPE-K demonstrates an electrical performance that is among the best that have been reported in the literature for OECT materials.
{"title":"Novel materials for organic electrochemical transistors","authors":"Thuc‐Quyen Nguyen","doi":"10.1117/12.2597204","DOIUrl":"https://doi.org/10.1117/12.2597204","url":null,"abstract":"Organic electrochemical transistors (OECTs) have been demonstrated in a wide range of applications such as analyte detection, neural interfacing, impedance sensing and neuromorphic computing. Majority of OECTs use PEDOT:PSS and liquid electrolytes. In this talk, I will discuss the development of biomaterials as solid state electrolytes and conjugated polyelectrolytes (CPEs) as semiconductors for OECTs. The biogels that consist of gelatin and glycerol with high ionic conductivity are used as solid electrolytes. We establish a relation between morphology and protonic-conductivity of the gels, allowing for the fabrication of gel-based OECTs with desirable functionalities, good ON/OFF ratio and transconductance, fast-switching speed, and good stability in ambient air. Anionic CPEs are used as mixed conductor materials for OECTs to replace PEDOT:PSS. CPE-based OECTs operate in the accumulation mode, which allows for much lower energy consumption in comparison to commonly used depletion mode PEDOT:PSS devices. The physical and electrical properties of CPE-K have been fully characterized to allow a direct comparison to other top performing OECT materials. CPE-K demonstrates an electrical performance that is among the best that have been reported in the literature for OECT materials.","PeriodicalId":175873,"journal":{"name":"Organic and Hybrid Field-Effect Transistors XX","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129476869","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}
{"title":"Rethinking the contact resistance bottleneck in organic and polymer thin-film transistors","authors":"A. Dodabalapur","doi":"10.1117/12.2597243","DOIUrl":"https://doi.org/10.1117/12.2597243","url":null,"abstract":"","PeriodicalId":175873,"journal":{"name":"Organic and Hybrid Field-Effect Transistors XX","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127626587","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}
The emerging research field of organic bioelectronics has developed rapidly over the last few years and elegant examples of biomedically important applications including for example in-vivo drug delivery and neural interfacing have been demonstrated. The organic electrochemical transistor (OECT), capable of transducing small ionic fluxes into electronic signals in an aqueous environment, is an ideal device to utilise in bioelectronic applications. To date, nearly all OECTs have been fabricated with commercially available PEDOT:PSS, heavily limiting the variability in performance. We have previously shown that tailor-made semiconducting polymers are fully capable of matching the performance of PEDOT:PSS. To capitalise on this discovery and the versatility of the organic chemistry toolbox, further materials development is needed. In my talk I will discuss our recent work in this area covering examples of both molecular and polymeric semiconducting materials and their performance in bioelectronic devices.
{"title":"New semiconductor design for organic electrochemical transistors","authors":"C. Nielsen","doi":"10.1117/12.2593416","DOIUrl":"https://doi.org/10.1117/12.2593416","url":null,"abstract":"The emerging research field of organic bioelectronics has developed rapidly over the last few years and elegant examples of biomedically important applications including for example in-vivo drug delivery and neural interfacing have been demonstrated.\u0000The organic electrochemical transistor (OECT), capable of transducing small ionic fluxes into electronic signals in an aqueous environment, is an ideal device to utilise in bioelectronic applications. To date, nearly all OECTs have been fabricated with commercially available PEDOT:PSS, heavily limiting the variability in performance. We have previously shown that tailor-made semiconducting polymers are fully capable of matching the performance of PEDOT:PSS. To capitalise on this discovery and the versatility of the organic chemistry toolbox, further materials development is needed. In my talk I will discuss our recent work in this area covering examples of both molecular and polymeric semiconducting materials and their performance in bioelectronic devices.","PeriodicalId":175873,"journal":{"name":"Organic and Hybrid Field-Effect Transistors XX","volume":"33 6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124412412","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}
Even though record organic semiconductor mobilities are reported for organic semiconductor single crystals, making thin film crystals remains difficult. We will show our efforts to understand crystal formation, epitaxy, and transport. In particular, we will discuss our efforts to realize pinhole free films of numerous organic semiconductors with 100s microns scale grains, and how the materials able to undergo a transition from amorphous to crystalline correlate well with thermal properties. Homoepitaxial studies uncover evidence of point and line defect formation in these films, indicating that homoepitaxy is not always strain-free. Transistors made out of large-grained films of rubrene display charge carrier mobility of up to 3.5 cm2 V–1 s–1, very close to single crystal values, highlighting their potential for practical application. Finally, we will show efforts in achieving heteroepitaxial growth of a different molecular material on top of a crystalline organic template.
{"title":"Formation, growth, and electronic properties of microcrystalline organic semiconductors","authors":"Barry P Rand","doi":"10.1117/12.2593271","DOIUrl":"https://doi.org/10.1117/12.2593271","url":null,"abstract":"Even though record organic semiconductor mobilities are reported for organic semiconductor single crystals, making thin film crystals remains difficult. We will show our efforts to understand crystal formation, epitaxy, and transport. In particular, we will discuss our efforts to realize pinhole free films of numerous organic semiconductors with 100s microns scale grains, and how the materials able to undergo a transition from amorphous to crystalline correlate well with thermal properties. Homoepitaxial studies uncover evidence of point and line defect formation in these films, indicating that homoepitaxy is not always strain-free. Transistors made out of large-grained films of rubrene display charge carrier mobility of up to 3.5 cm2 V–1 s–1, very close to single crystal values, highlighting their potential for practical application. Finally, we will show efforts in achieving heteroepitaxial growth of a different molecular material on top of a crystalline organic template.","PeriodicalId":175873,"journal":{"name":"Organic and Hybrid Field-Effect Transistors XX","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128289750","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}
A. Moulé, Tucker L. Murrey, Ian E. Jacobs, Z. I. Bedolla-Valdez, J. Saska, Goktug Gonel, Alice S. Fergerson, Nichole L. Yacoub, Rachel M. Talbot, Nikolay Shevchenko, M. Mascal, A. Salleo, Camila Cendra
Sequential solution doping is a processing technique that allows a conjugated polymer film to be doped from a solvent that will not dissolve the polymer. We present here a method to predict the film doping level in cm-3 from the solution concentration used to dope the film. We show using four polymers and three different and newly synthesized dopants that the doping level can me modeled using a simple Langmuir isotherm. In addition, analysis of the UV/vis spectra shows filling of the density of states. Polymers with a sharper band edge demonstrate much high conductivity for the same hole density. We analyze a series of DPP polymers and show how the polymer order changes as a function of the doping level. A second recent discovery is that the anion in sequentially doped films can be exchanged with another anion after doping. This means that the reactive molecule used to doped the polymer can be removed and replaced with a different ion that is not reactive. We present a multi-ion Langmuir isotherm model and show that the film doping level in mixed ion solutions can also be predicted.
{"title":"Understanding the driving force for solution molecular doping","authors":"A. Moulé, Tucker L. Murrey, Ian E. Jacobs, Z. I. Bedolla-Valdez, J. Saska, Goktug Gonel, Alice S. Fergerson, Nichole L. Yacoub, Rachel M. Talbot, Nikolay Shevchenko, M. Mascal, A. Salleo, Camila Cendra","doi":"10.1117/12.2595855","DOIUrl":"https://doi.org/10.1117/12.2595855","url":null,"abstract":"Sequential solution doping is a processing technique that allows a conjugated polymer film to be doped from a solvent that will not dissolve the polymer. We present here a method to predict the film doping level in cm-3 from the solution concentration used to dope the film. We show using four polymers and three different and newly synthesized dopants that the doping level can me modeled using a simple Langmuir isotherm. In addition, analysis of the UV/vis spectra shows filling of the density of states. Polymers with a sharper band edge demonstrate much high conductivity for the same hole density. We analyze a series of DPP polymers and show how the polymer order changes as a function of the doping level. A second recent discovery is that the anion in sequentially doped films can be exchanged with another anion after doping. This means that the reactive molecule used to doped the polymer can be removed and replaced with a different ion that is not reactive. We present a multi-ion Langmuir isotherm model and show that the film doping level in mixed ion solutions can also be predicted.","PeriodicalId":175873,"journal":{"name":"Organic and Hybrid Field-Effect Transistors XX","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128291726","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}
Silylethyne substitution is a versatile approach to control solubility and crystalline order in high aspect ratio chromophores such as acenes. We have developed some simple rules to predict crystal packing in such substituted systems, and these rules were more recently refined by careful computational analysis. We also found that trialkylgermylethynyl-substituted acenes and heteroacenes followed nearly identical rules to the silyl derivatives. Due to their lower cost and more versatile synthetic variability, we have now begun to prepare trialkyl-carbon substituted alkynes to use in the crystal engineering of acenes and heteroacenes. We were rather surprised to discover that these carbon-based systems did not follow the same rules for packing as the silyl or germyl alkynes. We will present a systematic study of acene crystal packing in relation to several classes of carbon-based alkyne systems, the low-cost, scalable syntheses of these alkynes, computational assessment of the resulting crystal packings, and FET studies of select materials. We have also expanded the dimensionality of the backbones under study by incorporating pyrene units - the impact of pyrene insertion on the electronic structure of acenes will be covered in detail.
{"title":"Exploring self-assembly in functionalized acenes","authors":"J. Anthony","doi":"10.1117/12.2593830","DOIUrl":"https://doi.org/10.1117/12.2593830","url":null,"abstract":"Silylethyne substitution is a versatile approach to control solubility and crystalline order in high aspect ratio chromophores such as acenes. We have developed some simple rules to predict crystal packing in such substituted systems, and these rules were more recently refined by careful computational analysis. We also found that trialkylgermylethynyl-substituted acenes and heteroacenes followed nearly identical rules to the silyl derivatives. Due to their lower cost and more versatile synthetic variability, we have now begun to prepare trialkyl-carbon substituted alkynes to use in the crystal engineering of acenes and heteroacenes. We were rather surprised to discover that these carbon-based systems did not follow the same rules for packing as the silyl or germyl alkynes. We will present a systematic study of acene crystal packing in relation to several classes of carbon-based alkyne systems, the low-cost, scalable syntheses of these alkynes, computational assessment of the resulting crystal packings, and FET studies of select materials. We have also expanded the dimensionality of the backbones under study by incorporating pyrene units - the impact of pyrene insertion on the electronic structure of acenes will be covered in detail.","PeriodicalId":175873,"journal":{"name":"Organic and Hybrid Field-Effect Transistors XX","volume":" 26","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132158071","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}
The charge carrier mobility in organic field-effect transistors (FETs) may be enhanced by a few orders of magnitude by an appropriate choice of the dielectric layer. Polymer ferroelectric dielectrics with their high dielectric constants are attractive for low-operating voltage FETs. However, due to the dynamic coupling of the charge carriers to the electronic polarization at the semiconductor-dielectric interface, polymer ferroelectric based organic FETs may result in low carrier mobilities. Selective electrical poling of the ferroelectric dielectric, poly(vinylidene fluoride trifluorethylene) (PVDF-TrFE), is seen to greatly improve the performance of small molecule and donor-acceptor copolymer based FETs [1]. A combination of vertical and lateral poling of the PVDF-TrFE layer, which reduces the gate leakage current as well as mitigates polarization fluctuation driven transport, yields carrier mobilities upwards of 1 cm2/Vs in TIPS-pentacene and 0.5 cm2/Vs in diketopyrrolopyrrole based FETs under ambient conditions [2]. Other strategies for improving the performance of FETs involve dissolving the ferroelectric polymer in high dipole moment solvents and adding thin polymer buffer layers. The incorporation of magnetic nanoparticles in non-ferroelectric dielectrics is yet another approach for enhancing the dielectric constant. Ferrite nanoparticles with biomimetic peptide nanostructures as gate dielectrics have ramifications in low-operating voltage organic FETs [3]. This work was supported by National Science Foundation under Grant No. ECCS-1707588 [1] Laudari et al. Adv. Mater. Interfaces 6, 1801787 (2019). [2] Laudari et al. ACS Appl. Mater. Interfaces 12, 26757 (2020). [3] Khanra et al. ACS Appl. Nano Mater 1, 1175 (2018).
{"title":"Processing polymer dielectrics for improved performance of organic field-effect transistors","authors":"S. Guha","doi":"10.1117/12.2594377","DOIUrl":"https://doi.org/10.1117/12.2594377","url":null,"abstract":"The charge carrier mobility in organic field-effect transistors (FETs) may be enhanced by a few orders of magnitude by an appropriate choice of the dielectric layer. Polymer ferroelectric dielectrics with their high dielectric constants are attractive for low-operating voltage FETs. However, due to the dynamic coupling of the charge carriers to the electronic polarization at the semiconductor-dielectric interface, polymer ferroelectric based organic FETs may result in low carrier mobilities. Selective electrical poling of the ferroelectric dielectric, poly(vinylidene fluoride trifluorethylene) (PVDF-TrFE), is seen to greatly improve the performance of small molecule and donor-acceptor copolymer based FETs [1]. A combination of vertical and lateral poling of the PVDF-TrFE layer, which reduces the gate leakage current as well as mitigates polarization fluctuation driven transport, yields carrier mobilities upwards of 1 cm2/Vs in TIPS-pentacene and 0.5 cm2/Vs in diketopyrrolopyrrole based FETs under ambient conditions [2]. Other strategies for improving the performance of FETs involve dissolving the ferroelectric polymer in high dipole moment solvents and adding thin polymer buffer layers. The incorporation of magnetic nanoparticles in non-ferroelectric dielectrics is yet another approach for enhancing the dielectric constant. Ferrite nanoparticles with biomimetic peptide nanostructures as gate dielectrics have ramifications in low-operating voltage organic FETs [3]. \u0000\u0000This work was supported by National Science Foundation under Grant No. ECCS-1707588\u0000\u0000[1] Laudari et al. Adv. Mater. Interfaces 6, 1801787 (2019).\u0000[2] Laudari et al. ACS Appl. Mater. Interfaces 12, 26757 (2020).\u0000[3] Khanra et al. ACS Appl. Nano Mater 1, 1175 (2018).","PeriodicalId":175873,"journal":{"name":"Organic and Hybrid Field-Effect Transistors XX","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129499242","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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