Switching Cycles Research Articles

In-situ growth all-inorganic bismuth-based perovskite single crystal hexagonal sheets for planar photodetector

Single crystal thin films can achieve the balance between thickness and mobility, which is widely used in the field of optoelectronic devices. Herein, lead-free perovskite Cs3Bi2I9 single crystal hexagonal sheets with preferred orientation along (002) were prepared by solution method. The Bi element is positively trivalent without oxidation in the single crystal hexagonal sheets. The growth processes of Cs3Bi2I9 crystal including nucleation and crystal growth are revealed by in-situ optical and structural observation. The Cs3Bi2I9 single crystal hexagonal sheets demonstrate excellent stability without encapsulation during long time exposure to the air. Obvious fluorescence quenching effect observed by steady-state and time-resolved photoluminescence measurement indicates charge transfer from Cs3Bi2I9 to ITO electrodes. Planar photodetectors based on Cs3Bi2I9 exhibit good photosensitive property, reproducibility and stability during multiple switching cycles. This work is conducive to lead-free perovskite regulation and further applications in photoelectronic devices.

Analysis of the Electrical ReRAM Device Degradation Induced by Thermal Cross‐Talk

AbstractA switching of resistive memory cells leads to a local accumulation of Joules heat in the device. In resistive RAM (ReRAM) arrays, the heat generated in one cell spreads via common electrode metal lines to the neighboring cells and may cause their performance degradation. The performance degradation results in reduced number of switching cycles and, in extreme cases, even in a loss of a bit, caused by the rupture of the nanofilament. The authors propose a thermal analysis of the thermal cross‐talk, describe its impact on cells’ electric performance, and identify three major mechanisms for the ReRAM reliability: (i) thermal conductivity, (ii) the specific heat capacity, and (iii) geometry of the electrodes. Several ReRAM arrays are manufactured to vary thermal conductivity, specific heat and geometry of the electrodes by depositing eight different inert electrodes: Pt(50 nm)/Ti(30 nm), Ru(50 nm)/Ti(30 nm), Co(50 nm)/Ti(30 nm), Pt(50 nm/Cu(100 nm)/Ti(30 nm), Pt(50 nm)/ Cu(200 nm)/Ti(30 nm), Ru(50 nm/Cr(30 nm), Ru(50 nm)/Ti(50 nm), and Rh(50 nm)/Cr(30 nm). The experimentally found differences of the degradation of electric performance of the array cells performed under identical circumstances can be correctly predicted by the proposed thermal analysis using the material properties and geometry parameters of the electrodes.

Memristors Based on Many-Layer Non-Stoichiometric Germanosilicate Glass Films

Nonstoichiometric GeSixOy glass films and many-layer structures based on them were obtained by high-vacuum electron beam vapor deposition (EBVD). Using EBVD, the GeO2, SiO, SiO2, or Ge powders were co-evaporated and deposited onto a cold (100 °C) p+-Si(001) substrate with resistivity ρ = 0.0016 ± 0.0001 Ohm·cm. The as-deposited samples were studied by Fourier-transformed infrared spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. A transparent indium–tin–oxide (ITO) contact was deposited as the top electrode, and memristor metal–insulator–semiconductor (MIS) structures were fabricated. The current–voltage characteristics (I–V), as well as the resistive switching cycles of the MIS, have been studied. Reversible resistive switching (memristor effect) was observed for one-layer GeSi0.9O2.8, two-layer GeSi0.9O1.8/GeSi0.9O2.8 and GeSi0.9O1.8/SiO, and three-layer SiO2/a–Ge/GeSi0.9O2.8 MIS structures. For a one-layer MIS structure, the number of rewriting cycles reached several thousand, while the memory window (the ratio of currents in the ON and OFF states) remained at 1–2 orders of magnitude. Intermediate resistance states were observed in many-layer structures. These states may be promising for use in multi-bit memristors and for simulating neural networks. In the three-layer MIS structure, resistive switching took place quite smoothly, and hysteresis was observed in the I–V characteristics; such a structure can be used as an “analog” memristor.

Observation of electrical threshold switching behavior and thermal crystallization in bulk Se86-xTe14Snx chalcogenide glasses

Selenium-rich chalcogenides have gained popularity as materials for selector devices due to their unique Ovonic Threshold Switching behavior. Bulk Se86-xTe14Snx glassy alloys (0 ≤ x ≤ 6) were prepared through the traditional melt quenching method. The samples with Sn atomic percentage (x) = 3 to 6 are found to exhibit a rapid and reversible transition between a highly resistive and conductive state affected by an electric field. A remarkable decrement in threshold voltage (Vth) from 453 V to 62 V has been observed with increase in the Tin content. Differential scanning calorimetry (DSC) analysis was carried out to understand the variation of Glass transition temperature (Tg), Crystallization temperature (Tc), and other important glass stability parameters and their compositional dependence. Se82Te14Sn4 sample was found to be thermally most stable with Herby’s parameter value (HR) of 0.3860 and a maximum number of switching cycles at room temperature. X-Ray diffraction patterns of annealed samples were compared with pristine glass to study the multi-phasic Se–Te–Sn alloy. Further, the threshold voltage (Vth) and the number of threshold switching cycles are found to decrease with an increase in temperature till crystallization on-set temperature (Toc). The temperature-dependent conductivity studies showed an abrupt increase in the conductivity of the samples as the temperature crossed the crystallization onset temperature.

Electrical characterization of sol-gel La2Ti2O7 films for resistive random access memory applications

The bipolar resistive switching (BRS) devices were investigated for RRAM applications in a MIM structure based on sol-gel derived amorphous La2Ti2O7 (LTO) thin films. The influences on the resistive switching (RS) properties according to the film thickness, electrode, annealing temperature and post metal annealing (PMA) treatment were also discussed. Moreover, RS performance of the RRAMs is affected by the work functions of electrodes. The RS characteristics of the devices are controlled by oxygen vacancies and the content of oxygen vacancies was seriously reduced after annealing, which led to a significant decrease of the endurance. In addition, PMA treatment increased the content of oxygen vacancies attributed to the forming of AlOx interface layer and made Al ions diffuse into the films to form bridges, which improved the RS performance of the devices. Consequently, the sample with 300 °C PMA exhibits the optimized RS properties with maximum switching cycles of 2674, a Ron/Roff ratio of 102, low operating voltages (VSet/VReset = 1.32 V/−1.21 V), and a retention time of over 104 s at room temperature and 85 °C, indicating the promising potential for practical RRAM applications. Conduction mechanism of all devices with Al top electrode were described by trap-controlled space-charge limited current (SCLC) and ohmic conduction.

An Improved Auxiliary Resonant Commutated Pole Inverter With Low Loss of Energy Recovery

This brief proposes an improved auxiliary resonant commutated pole inverter (ARCPI) to optimize the transmission efficiency of the inverter. During the commutation process of the inverter, main switches can acquire zero-voltage switching and auxiliary switches can acquire zero-current switching, bringing about the significant reduction of switching loss. Besides, when the resonant state suspends in each switching cycle, the surplus energy in the resonant inductor will be fed back to the energy-storage capacitor through only one auxiliary diode, making for low loss of energy recovery. This brief illustrates each working state in a switching cycle. The relative experimental waveform indicates that switches acquire soft-switching. The efficiency of the proposed inverter achieves 99.1% at rated output power. Thus, the proposed inverter can have efficiency superiority over other similar inverters.

H-Bridge Derived Topology for Dynamic On-Resistance Evaluation in Power GaN HEMTs

Gallium nitride high electron mobility transistors outperform Silicon devices due to their excellent physical properties. However, being an immature technology, it exhibits dynamic <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -state resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R_{\text{ds}, \text{on}}$</tex-math></inline-formula> ). This causes increased conduction loss and leads to reduced operating efficiency. To evaluate the dynamic <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R_{\text{ds}, \text{on}}$</tex-math></inline-formula> of the device, a measurement circuit is required. In literature, a standardized double pulse test is widely used for the measurement of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R_{\text{ds}, \text{on}}$</tex-math></inline-formula> . However, due to the uncontrolled <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> -state time and inability to independently adjust, the test conditions result in restricted measurement. This article proposes a measurement circuit of the device in power electronics operations. The circuit uses an H-Bridge-derived topology with capacitive storage to enable forward and reverse conduction mode measurement of the device. In all the modes, the circuit allows measurement from the first switching cycle and independent control over the testing conditions by using a hysteresis current control. The proposed measurement circuit is validated using simulation and experimentation. Finally, analytical efficiency compared with the state-of-the-art measurement circuits is provided.

Non-Backflow-Power and Reduced-Switching-Loss Modulation for Bidirectional Series Resonant Converter With Wide Gain Range

In the achievement of high power efficiency over a wide gain range for a bidirectional series resonant converter (BSRC), conduction losses caused by backflow power and switching losses are two challenges. In this article, a novel modulation of the BSRC is proposed for a wide voltage gain range and high efficiency as well. With the proposed modulation, the BSRC can operate in both buck- and boost-like modes for a wide gain range. The resonant current is in phase with the terminal voltage on both primary and secondary sides, to eliminate the backflow power for the reduction of conduction losses. Hard turn-off problem is alleviated with a resonant current fully released before the completion of the switching cycle. Thus, the number of hard switching actions is significantly reduced compared with existing modulation schemes in the literature. A control scheme based on state-flowchart is also proposed to realize seamless transition among different working modes. To validate the proposed modulation, a 1 kVA prototype of BSRC is developed and interfaces a high-voltage bus ranging from 240 to 480 V and a low-voltage bus ranging from 24 to 56 V. Compared with conventional modulation schemes, efficiency enhancement can be observed over the whole operating range.

Design and fabrication of a series contact RF MEMS switch with a novel top electrode

Radio-frequency (RF) micro-electro-mechanical-system (MEMS) switches are widely used in communication devices and test instruments. In this paper, we demonstrate the structural design and optimization of a novel RF MEMS switch with a straight top electrode. The insertion loss, isolation, actuator voltage, and stress distribution of the switch are optimized and explored simultaneously by HFSS and COMSOL software, taking into account both its RF and mechanical properties. Based on the optimized results, a switch was fabricated by a micromachining process compatible with conventional IC processes. The RF performance in the DC to 18 GHz range was measured with a vector network analyzer, showing isolation of more than 21.28 dB over the entire operating frequency range. Moreover, the required actuation voltage was about 9.9 V, and the switching time was approximately 33 μs. A maximum lifetime of 109 switching cycles was obtained. Additionally, the dimension of the sample is 1.8 mm × 1.8 mm × 0.3 mm, which might find application in the current stage.

One‐cycle controllability of high step‐up Boost converter with coupled inductor

SummaryComparing with traditional pulse width modulation technique, the transient performances of the high step‐up DC/DC converters can be significantly improved by one‐cycle control (OCC) technique, which is an appropriate control strategy for interface converters directly connecting the renewable energies to the DC microgrid. However, the suitability of OCC for these converters is rarely studied. One‐cycle controllability of the high step‐up DC/DC Boost converter with coupled inductor is studied with theoretical researches and experimental verifications. First, with the analysis on the operating modes of the converter, its periodic switched linear system model and the criterion for OCC are established. Furthermore, one‐cycle controllability of the converter is calculated in detail. Final, a prototype of the high step‐up converter from 48 to 380 V is prepared. Experimental results indicate that the disturbances in the input of the high step‐up converter can be depressed within only one switching cycle. Ideal dynamic characteristic for the converter under disturbance in the output is also achieved. Results of this paper are meaningful for investigations on the transient characteristics of high step‐up DC/DC converters applied to DC microgrid.

In Situ Modification of Multi-Walled Carbon Nanotubes with Polythiophene-Based Conjugated Polymer for Information Storage.

One-dimensional multi-walled carbon nanotubes (MWNTs) have unique electrical properties, but they are not solution-processable, which severely limits their applications in microelectronic devices. Therefore, it is of great significance to improve the solubility of MWNTs and endow them with new functions by chemical modification. In this work, MWNTs were in situ functionalized with poly[(1,4-diethynyl-benzene)-alt-(3-hexylthiophene)] (PDHT) via Sonogashira-Hagihara polymerization. The obtained material PDHT-g-MWNTs was soluble in conventional organic solvents. By sandwiching a PDHT-g-MWNTs film between Al and ITO electrodes, the fabricated Al/PDHT-g-MWNTs/ITO electronic device exhibited nonvolatile rewritable memory behavior, with highly symmetrical turn-on/off voltages, a retention time of over 104 s, and durability for 200 switching cycles. These findings provide important insights into the development of carbon nanotube-based materials for information storage.

Investigation of Different Oxygen Partial Pressures on MgGa2O4-Resistive Random-Access Memory.

Different oxygen partial-pressure MgGa2O4-resistive RAMs (RRAMs) are fabricated to investigate the resistive switching behaviors. The X-ray photoelectron spectroscopy results, set voltage, reset voltage, cycling endurance, and retention time are drawn for comparison. With the increasing oxygen ratio gas flow, the resistive switching characteristics of MgGa2O4 RRAM are drastically elevated by changing the fabrication conditions of the RS layer. Moreover, we portray a filament model to explain the most likely mechanism associated with the generation and rupture of conductive filaments composed of oxygen vacancies. The formation of the interfacial layer (AlO x ) and the participation of the Joule heating effect are included to explain the highly distributed high-resistance state (HRS). The high randomness among switching cycles for memory application should be prevented, but it is suitable for the physical unclonable function. The relationship between HRS and the next time set voltage shows a strong correlation, and the conduction mechanisms of the low-resistance state (LRS) and HRS correspond to ohmic conduction and space charge-limited conduction, respectively. Meanwhile, the RRAM undergoes 10,000 s retention tests, and the two resistance states can be distinguished without obvious alternation or degradation. A favorable cycling endurance and retention time achieved by optimizing the fabrication parameters of Al/MgGa2O4/Pt RRAM have the potential for nonvolatile memristors and information security applications.

An asymmetric-square-wave voltage injection method for online inductance identification of PMSM under sensorless control

In this paper, an online inductance identification method for PMSM, which is embedded into the flux-estimation-based sensorless control, is proposed. By injecting a periodic voltage where a larger negative voltage lasts one switching cycle, and a smaller positive voltage lasts several switching cycles, the extra voltage equation is established. Then, the q-axis current can be decomposed to an asymmetric triangular wave component and a low frequency component. Using the triangular wave current and the voltage equation, an inductance identification algorithm is designed. Since the injected positive voltage can be smaller, this method overcomes the difficulty that the symmetric square wave voltage cannot be injected at high-speed range, thus expanding the application of the inductance identification. And since the triangular wave current can be accurately extracted, the interference caused by back-EMF is eliminated. The simulation results demonstrate the effectiveness of the method.

Reduction of leakage current and large enhancement of ferroelectric properties in Sb doped Bi4Ti3O12 ferroelectric thin film with Sb doped Bi2Ti2O7 as buffer layer

Perovskite phase ferroelectric thin films Bi4-xSbxTi3O12 (Sb ( x )-BIT) and pyrochlore crystal phase thin films Bi2-ySbyTi2O7 (Sb ( y )-BTO) with different Sb concentration have been fabricated on Pt(111)/Ti/SiO2/Si(100) substrates through sol-gel method respectively. Test results show that the doping Sb can significantly reduce the leakage current of films. Especially when x = 0.04, y = 0.3 the leakage current characteristics of Sb ( 0.04 )-BIT and Sb ( 0.3 )-BTO both to achieve the optimal, and the ferroelectric properties Sb ( 0.04 )-BIT are also improved. By the same means, constructed the Sb ( 0.04 )-BIT / Sb ( 0.3 )-BTO system with Sb ( 0.3 )-BTO as buffer layer and Sb ( 0.04 )-BIT as ferroelectric layer. The properties of BIT ferroelectric thin films are improved by the doping of Sb element and the addition of buffer layer. This is mainly reflected in that compared to pristine BIT the leakage current of Sb ( 0.04 )-BIT / Sb ( 0.3 )-BTO system decreases rapidly from the initial 8.8 × 10−4 A/cm2 to the current 7.2 × 10−10 A/cm2, the residual polarization 2Pr of the system increases sharply from 9.5 to 70.8 µC/cm2 and fatigue endurance up to more than 1010 switching cycles.

A Universal Multicarrier Multisampling Method for Digitally Controlled Inverters

For reducing the control delays introduced by the digital control of dc/ac converters, multisampling technology applying high sampling frequency of exact multiples of the switching frequency becomes attractive. In this way, higher control bandwidth and stability margin are achievable. However, multiupdate (>2) of the modulation signal within one switching cycle is not usually allowed on the digital signal processors. Besides, multiupdate within one switching cycle leads to an abnormal phenomenon referred to as vertical crossing when the modulation signal intersects the carrier signal vertically. The vertical crossing further causes the deadband effect of the pulsewidth-modulation signal and distortion of the output waveform. The abovementioned phenomenon greatly restricts the application of multisampling technology. In order to break the aforementioned barriers, a novel multicarrier-based multisampling method by dividing the triangular carrier signal into <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> equal sawtooth segments is proposed in this article. Moreover, the problem of vertical crossings and the resulting deadband effect in the multiupdate mode is solved. Simulation and experimental results on a single-phase dc–ac inverter are provided to validate the effectiveness of the proposed approach.

Soft-Switching Operation With a Variable Switching Frequency Control for Switched-Quasi-Z-Source Bidirectional DC–DC Converter in EVs

The switched-quasi-Z-source bidirectional dc–dc converter (SQBC) has the characteristics of wide voltage gain and low voltage stress, and is suitable for the power interface between the supercapacitors and the dc bus in the multisource system of electric vehicles. On the basis of the SQBC, an optimal design method for inductance parameters and variable switching frequency control strategy are proposed in this article. While remaining the wide voltage gain and low voltage stress characteristics of the topology, the soft-switching operation within the full voltage gain range is achieved without adding additional auxiliary devices. The variable switching frequency control strategy keeps the converter operating at the critical soft-switching point with the lowest switching losses per switching cycle, further improving the operation efficiency of the converter. Finally, an experimental prototype with a rated power of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> = 300 W, input voltage of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">low</sub> = 50–150 V and output voltage of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">high</sub> = 300 V was built, and its maximum efficiency is 98.28%, which verified the correctness and effectiveness of the proposed method.

Experimental Assessment of a Tiny AI-Empowered Output Filter Parameter Extraction Framework for Digital Power

An experimental assessment of a “plug-and-play” tiny artificial-intelligence-empowered output filter parameter extraction framework for digital power is presented. The framework can be incorporated into an existing digital controller to perform online parameter extraction without adding extra sensors or modifying the power conversion stage. The idea is based on firstly transferring the control from the default control law to the framework, which consists of a predefined control law to perform output regulation for a few switching cycles, then introducing a small-signal perturbation into the control signal, and finally utilizing a long short-term memory (LSTM) network to recognize the dynamic response of the control signal to perform either regression or classification of filter parameters. The LSTM network is trained with a reconfigurable output filter. The proposed framework has been successfully evaluated on a 240W, 100V/48V buck DC/DC converter prototype. The framework’s performance is studied by extracting the parameters of a second-order output filter and a fourth-order output filter. For the second-order output filter, the root-mean-square errors (RMSEs) in performing the filter inductor and capacitor regressions are 2.35% and 2.25%, respectively, and the F1-scores in classifying the inductance and capacitance are 0.805 and 0.815, respectively. The framework occupies 0.93% of the memory space of the controller with 512kB flash memories. The extraction time is 17.3ms. For the fourth-order filter, the maximum RMSEs in performing the regression of the filter inductors and capacitors are 2.04% and 6.49%, respectively. The framework occupies 3.62% of the memory space and the extraction time is 328ms.

High Step-Up SEPIC-Based Trans-Inverse DC–DC Converter With Quasi-Resonance Operation for Renewable Energy Applications

This article proposes a new single switch trans-inverse high step-up converter applicable in sustainable sources of energies such as photovoltaic (PV) and fuel cell (FC). Through developing a single-ended primary-inductor converter by a three-winding built-in transformer (BIT) mixed with a switched-capacitor voltage multiplier cell, high voltage gains as well as low voltage stress across the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> can be achieved to reduce the required duty cycle and the conduction losses. The third winding of the BIT acts in a trans-inverse manner whose turns ratio should be lower than unity. Hence, with a lower number of windings the voltage gain can also be improved. Furthermore, the quasi-resonance operation of the proposed converter, reduces the associated switching losses of the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> and also guarantees zero current switching of diodes through the whole switching cycle. Meanwhile, low input current of the proposed converter serves as an interesting feature to maintain PV and FC lifetime. The detailed steady-state analysis of the proposed high-efficiency converter is presented with an extensive performance comparison to explore its advantages. Finally, a 200-W prototype with 20–250-V voltage conversion is developed in the laboratory to examine the carried steady-state analysis.

Degradation and Recovery of GaN HEMTs in Overvoltage Hard Switching Near Breakdown Voltage

GaN high electron mobility transistors (HEMTs) have limited avalanche capability and usually fail catastrophically in voltage overshoot up to their dynamic breakdown voltage (BV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dyn</sub> ). This article presents the first comparative study of the parametric shift and recovery of three mainstream GaN HEMTs in repetitive overvoltage switching near their BV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dyn</sub> . In each switching cycle, a voltage overshoot up to 90% of BV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dyn</sub> was applied during the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> process. As the switching prolongs, all devices showed shifts in threshold voltage and saturation current, and these shifts saturated in less than 1-million cycles. These shifts are believed to be induced by the trapping of the holes generated in the impact ionization (I. I.). The device's poststress recovery was found to be dominated by the hole detrapping and through-gate removal, which highly depends on the gate stack. The gate injection transistor showed a fast natural recovery benefitted from the efficient hole removal through the Ohmic gate. The hole detrapping in the Schottky-type p-gate HEMT can be described by the Poole–Frenkel emission, allowing for the accelerated recoveries at negative gate bias and high temperatures. The hole removal in the metal-insulator-semiconductor (MIS) HEMT is blocked by the gate insulator, preventing a natural recovery. The MIS-HEMT can be recovered by applying positive gate and substrate biases, which facilitate the hole recombination in the channel. This article shows the good overvoltage robustness of all three GaN HEMTs and unveils effective methods for their poststress recovery, as well as suggests the significant impacts of I. I. and hole dynamics on the overvoltage ruggedness of GaN HEMTs near BV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dyn</sub> .

Quantitative determination of the full switching cycle of photochromic fluorescent proteins.

In this study, we develop a general analytical model of the photochromism of fluorescent proteins and apply it to spectroscopic measurements performed on six different labels. Our approach provides quantitative explanations for phenomena such as the existence of positive and negative switching, limitations in the photochromism contrast, and the fact that initial switching cycles may differ from subsequent ones. It also allows us to perform the very first measurement of all four isomerization quantum yields involved in the switching process.