Display pixels comprising light-emitting diodes and display screens comprising such display pixels

Abstract

Display pixels comprising light-emitting diodes and display screen comprising such display pixels. This description relates to a display pixel (12i,j) comprising at least first and second light-emitting diodes (LEDs), a first controllable current source (CS_B) supplying said first light-emitting diode (LED) with a first current, a second controllable current source (CS_R) supplying said second light-emitting diode (LED) with a second current, and an electronic circuit (40) comprising a storage circuit (48) for storing at least the first and second color signals (R,B) and a control circuit (50) configured to control the first controllable current source (CS_B) to supply the first current by pulse-width modulation from the first color signal (B) and configured to control the second controllable current source (CS_R) to supply the second current by linear control from the second color signal (R). Figure for the abstract: 3,

Description

Title of the invention: Display pixels comprising light-emitting diodes and display screen comprising such display pixels. Technical field

[0001] This description relates to a display pixel comprising light-emitting diodes and a display screen comprising such display pixels. Prior art

[0002] A pixel of an image corresponds to the unit element of the image displayed by a display screen. For displaying color images, the display screen generally comprises, for the display of each pixel of the image, at least three components, also called display subpixels, each of which emits light, called the color component of the image pixel, essentially in a single color (for example, red, green, and blue). The superposition of the color components of the image pixel emitted by the three display subpixels provides the observer with the color sensation corresponding to the pixel of the displayed image. In this case, the set formed by the three display subpixels used for displaying a pixel of an image is called the display pixel of the display screen. Each display subpixel may include a light source, in particular a light-emitting diode.

[0003] The display pixels can be arranged in a matrix, each display pixel being located at the intersection of a row and a column of the matrix. Electrodes are provided along the rows and columns to connect each display pixel to control circuits. In general, each row of display pixels is successively selected by a signal transmitted along the row electrodes, and the display pixels of the selected row are programmed to display the desired image pixels by signals transmitted along the column electrodes.

[0004] It is known to control a light-emitting diode (LED) by pulse-width modulation, also called PWM (Pulse Width Modulation). This type of control consists of passing successive current pulses of constant intensity through the LED, the pulses being repeated cyclically, the duty cycle determining the light intensity emitted by the LED. Such control advantageously allows the LED to operate at its optimal operating point where the efficiency of the LED is equal to The ratio between the light output of the LED and the electrical power consumed by the LED is maximized. Furthermore, pulse-width modulation (PWM) control maintains a constant current density through the LED. This is advantageous because, for some types of LEDs, the central wavelength of the emitted light can vary with the current density.

[0005] Some of the display subpixels of the display pixel may include a photoluminescent block covering the light-emitting diode. The photoluminescent block comprises phosphors capable, when excited by the light emitted by the associated light-emitting diode, of emitting light at a wavelength different from that of the light emitted by the associated light-emitting diode. The light conversion performance of certain types of phosphors, for example quantum dots, may decrease over time as a function of the maximum luminous flux received by the quantum dots. Therefore, it may be desirable to control the light-emitting diode covered by such a photoluminescent block so as to reduce the maximum luminous flux emitted by the light-emitting diode. Summary of the invention

[0006] An object of an embodiment is to provide a display pixel comprising light-emitting diodes and a display screen comprising such display pixels which overcome all or part of the disadvantages of existing display pixels comprising light-emitting diodes and display screens comprising such display pixels.

[0007] One embodiment provides a display pixel comprising at least first and second light-emitting diodes, a first controllable current source supplying said first light-emitting diode with a first current, a second controllable current source supplying said second light-emitting diode with a second current, and an electronic circuit comprising a storage circuit for storing at least the first and second color signals and a control circuit configured to control the first controllable current source to supply the first current by pulse-width modulation from the first color signal and configured to control the second controllable current source to supply the second current by linear control from the second color signal.

[0008] Such a control advantageously allows the first light-emitting diode to operate at its optimal operating point where the efficiency The intensity of the first LED is maximized. Furthermore, pulse-width modulation (PWM) control maintains a constant current density through the first LED. This is advantageous because the central wavelength of the radiation emitted by the first LED can vary with its current density. Additionally, linear control of the second LED is beneficial because it prevents it from constantly emitting radiation at its highest intensity, which could be detrimental, particularly when the second LED is coated with a photoluminescent block containing quantum dots.

[0009] According to one embodiment, the display pixel further comprises a third light-emitting diode (LED) and a third controllable current source supplying said third LED with a third current. The storage circuit is configured to store a third color signal, and the control circuit is configured to control the third controllable current source to provide the third current via linear control based on the third color signal. Linear control of the third LED is advantageous because it allows the third LED to avoid always emitting radiation at the highest intensity, which could be detrimental, particularly when the third LED is covered with a photoluminescent block comprising quantum dots.

[0010] According to one embodiment, the first color signal is a digital signal and the storage circuit includes first memory cells for storing the bits of the first color signal.

[0011] According to one embodiment, the second color signal is a digital signal and the storage circuit includes second memory cells to store the bits of the second color signal.

[0012] According to one embodiment, the control circuit includes a digital-to-analog converter configured to convert the second color signal stored in the second memory cells into an analog control signal to control the second current source.

[0013] According to one embodiment, the first color signal is an analog signal and the storage circuit includes a first capacitor to store the first color signal.

[0014] According to one embodiment, the second color signal is an analog signal and the storage circuit includes a second capacitor to store the second color signal.

[0015] According to one embodiment, each of the first and second light-emitting diodes comprises several elementary light-emitting diodes, each having an active area covering a three-dimensional semiconductor element corresponding to a wire, conical, frustoconical, or pyramidal element on the order of nanometers or micrometers. For such three-dimensional radial-type light-emitting diodes, the central wavelength of the radiation emitted by the light-emitting diode can vary significantly depending on the current density through the light-emitting diode. A pulse-width modulation control makes it possible to maintain a constant current density through the first light-emitting diode, which is advantageous when the first light-emitting diode is not covered by a photoluminescent block.

[0016] In one embodiment, the second light-emitting diode is covered by a first photoluminescent block. In another embodiment, the first light-emitting diode is configured to emit a first radiation at a first wavelength, the second light-emitting diode is configured to emit a second radiation at a second wavelength, and the first photoluminescent block is configured to convert the second radiation into a third radiation at a third wavelength, different from the second wavelength. The first photoluminescent block absorbs the second radiation emitted by the second light-emitting diode and emits the third radiation at a central wavelength different from the central wavelength of the second radiation emitted by the second light-emitting diode.Linear control of the second LED can cause a variation in the current density supplied to the second LED and, consequently, a variation in the center wavelength of the second beam emitted by the second LED. However, the first LED can emit the third beam with a fixed center wavelength even if the center wavelength of the second beam emitted by the second LED is dispersed. Therefore, the center wavelength of the third beam emitted by the first LED remains fixed even if the center wavelength of the second beam emitted by the second LED varies.

[0017] According to one embodiment, the first wavelength is equal to the second wavelength to within 10%. The first and second LEDs can advantageously be LEDs manufactured using the same process. The manufacturing process for the display pixel is therefore simpler.

[0018] According to one embodiment, the first photoluminescent block comprises first quantum dots. The light conversion performance of the first quantum dots tends to decrease over time as a function of the maximum luminous flux received by the first quantum dots. Linear control of the second light-emitting diode (LED) advantageously limits the luminous flux on the first quantum dots compared to pulse-width modulation control. Consequently, the first quantum dots do not always receive a second radiation from the second LED at the highest intensity. The durability of the light conversion performance of the first quantum dots is therefore increased.

[0019] In one embodiment, the third light-emitting diode is covered by a second photoluminescent block. In another embodiment, the third light-emitting diode is configured to emit a fourth radiation at a fourth wavelength, and the second photoluminescent block is configured to convert the fourth radiation into a fifth radiation at a fifth wavelength, different from the fourth wavelength. The second photoluminescent block absorbs the fourth radiation emitted by the third light-emitting diode and emits the fifth radiation at a central wavelength different from the central wavelength of the fourth radiation emitted by the third light-emitting diode.Linear control of the third LED can cause a variation in the current density supplied to the third LED and, consequently, a variation in the center wavelength of the fourth beam emitted by the third LED. However, the second LED can emit the fifth beam with a fixed center wavelength even if the center wavelength of the fourth beam emitted by the third LED is dispersed. Therefore, the center wavelength of the fifth beam emitted by the second LED remains fixed even if the center wavelength of the fourth beam emitted by the third LED varies.

[0020] According to one embodiment, the fourth wavelength is equal to the first wavelength within 10%. The first and third LEDs can advantageously be LEDs manufactured using the same process. The manufacturing process for the display pixel is therefore simpler.

[0021] According to one embodiment, the second photoluminescent block comprises second quantum dots. The light conversion performance of the second quantum dots tends to decrease over time as a function of the Maximum luminous flux received by the second quantum dots. Linear control of the third LED advantageously limits the luminous flux at the second quantum dots compared to pulse-width modulation control. Consequently, the second quantum dots do not always receive radiation from the second LEDs at the highest intensity. The durability of the light conversion performance of the second quantum dots is therefore increased.

[0022] According to one embodiment, the display pixel comprises a first integrated circuit including the electronic circuit comprising said storage circuit and the control circuit.

[0023] According to one embodiment, the display pixel comprises an optoelectronic circuit fixed to the integrated circuit, the optoelectronic circuit comprising the first and second light-emitting diodes.

[0024] One embodiment also provides a display screen comprising: display pixels as defined above; the first electrodes coupled to the control circuits of the display pixels; a first circuit to provide a selection signal on each first electrode for the selection of the display pixels coupled to the first electrode; second electrodes coupled to the electronic circuits of the display pixels; and a second circuit to provide data signals on the second electrodes.

[0025] According to one embodiment, the second circuit is configured to provide the data signals on the second electrodes in the form of analog signals.

[0026] According to one embodiment, the second circuit is configured to provide data signals on the second electrodes in the form of digital signals.

[0027] According to one embodiment, the second circuit is configured to provide data signals on the second electrodes, comprising an alternation of digital and analog signals. Brief description of the drawings

[0028] The aforementioned features and advantages, as well as others, will be described in detail in the subsequent disclosure of specific embodiments given by way of illustration and not limitation with reference to the accompanying drawings, in which:

[0029] [Fig.1] partially and schematically represents an embodiment of a display screen;

[0030] [Fig.2] is a very simplified cross-sectional view of an embodiment of a display pixel;

[0031] [Fig.3] represents a functional diagram of a display pixel of the screen of [Fig.1];

[0032] [Fig.4] represents a functional diagram of a light emission circuit for the display pixel of [Fig.3];

[0033] [Fig.5] represents a functional diagram of another embodiment of the light emission circuit of the display pixel of [Fig.3];

[0034] [Fig.6] represents a functional diagram of a part of the display pixel of [Fig.3];

[0035] [Fig.7] represents a functional diagram of another embodiment of a part of the display pixel of [Fig.3];

[0036] [Fig.8] represents examples of time diagrams of signals of the display pixel of [Fig.7] according to an embodiment of a method of operating the display screen;

[0037] [Fig.9] represents a functional diagram of another embodiment of a part of the display pixel of [Fig.3];

[0038] [Fig. 10] represents examples of time diagrams of display pixel signals of [Fig. 9] according to another embodiment of a method of operating the display screen;

[0039] [Fig.1 1] represents, partially and schematically, a more detailed embodiment of the display pixel represented in [Fig.2];

[0040] Figure 12 represents an embodiment of a three-dimensional light-emitting diode; and

[0041] [Fig. 13] represents another embodiment of a three-dimensional light-emitting diode. Description of the implementation methods

[0042] Unless otherwise specified, when reference is made to two elements connected together, this means a direct connection without any intervening elements other than conductors, and when reference is made to two elements coupled together, this means that these two elements can be connected or coupled through one or more other elements. Furthermore, a signal that alternates between a first constant state, for example a logic low state, denoted "0", and a second constant state, for example a logic high state, denoted "1", is called a "binary signal". The high and low states of the different binary signals in the same electronic circuit can be different. In practice, binary signals can correspond to voltages or currents that may not be perfectly constant in the high or low state.

[0043] Furthermore, unless otherwise specified, when referring to a voltage at a conductive contact, the difference between the potential at said conductive contact and a reference potential, for example earth, considered to be equal to 0 V. When radiation has a spectrum of general "bell-shaped" form, for example of Gaussian form, having a maximum, the wavelength at which the maximum of the spectrum is reached is called the wavelength of the radiation, or central or principal wavelength of the radiation.

[0044] Unless otherwise specified, the expressions "approximately", "roughly", "about" and "in the order of" mean within 10%, and preferably within 5%. Furthermore, the expression "varyingly constant" means that it varies by less than 10% over time from a reference value.

[0045] A light-emitting diode is said to be three-dimensional when it comprises a three-dimensional semiconductor element of micrometer or nanometer size extending in a preferred direction, for example a microwire or a nanowire, covered with an active area. In particular, a three-dimensional light-emitting diode is said to be radial when its active area extends at least onto the lateral walls of the three-dimensional semiconductor element.

[0046] Figure 1 partially and schematically represents a known example of a display screen 10. The display screen 10 comprises display pixels 12^, for example, arranged in M ​​rows and N columns, M being an integer from 1 to 8000 and N being an integer from 1 to 16000, i being an integer from 1 to M, and j being an integer from 1 to N. By way of example, in Figure 1, M and N are equal to 6. Each display pixel 1¾ is coupled to a source of a low reference potential Gnd, for example earth, via an electrode 14; and to a source of a high reference potential Vcc via an electrode 16j. By way of example, the electrodes 14; are aligned along the rows of [Fig.l] and the 16j electrodes are aligned along the columns of [Fig.l], the reverse arrangement being possible.The display screen's supply voltage is the voltage between the high reference potential (Vcc) and the low reference potential (Gnd), and is denoted Vcc as the high reference potential. The supply voltage Vcc depends in particular on the arrangement of the LEDs and the technology used to manufacture them. For example, the supply voltage Vcc can be in the range of 4 V to 5 V.

[0047] For each row, the display pixels 12j of the row are coupled to a row electrode 18j. For each column, the display pixels 1¾ of the column are coupled to a column electrode 20j. The display screen 10 includes a selection circuit 22 coupled to the row electrodes 18j and adapted to provide a Corn selection signal on each row electrode 18j. The display screen 10 includes a data transmission circuit 24 coupled to the column electrodes 20j and adapted to transmit a Dataj data signal on each column electrode 20j. The selection circuit 22 and control circuit 24 are controlled by a circuit 26, comprising for example a microprocessor.

[0048] Figure 2 is a highly simplified cross-sectional view of a known example of a display pixel 1¾. Each display pixel 1¾ comprises a control circuit 30 covered by a display circuit 32. The display circuit 32 comprises light-emitting diodes, preferably at least three LEDs. The display pixel comprises a lower surface 34 and an upper surface 35 opposite the lower surface 34, the surfaces 34 and 35 preferably being planar and parallel. The control circuit 30 further comprises conductive pads P_Gnd, P_Vcc, P_Col, P_Row on the lower surface 34. The control circuit 30 may be an integrated circuit comprising electronic components, in particular insulated-gate field-effect transistors, also known as MOS transistors, or thin-film transistors, also known as TFTs.Preferably, the display circuit 32 comprises only LEDs and the conductive elements of these LEDs, and the control circuit 30 comprises all the electronic components necessary for controlling the LEDs of the display circuit 32. Alternatively, the display circuit 32 may also include other electronic components in addition to the LEDs. In one embodiment, each LED comprises several three-dimensional LEDs. In [Fig. 2], the LEDs are shown as being connected to a common anode. However, it may be desirable to arrange the LEDs in a different configuration. For example, the LEDs may be connected to a common cathode or be connected independently of each other.

[0049] Each conductive pad P_Gnd, P_Vcc, P_Col, P_Row is intended to be connected to one of the electrodes 14, 16j, 18, 20j shown schematically in [Fig. 2]. The first conductive pad P_Gnd is coupled to the source of the low reference potential Gnd. The second conductive pad P_Vcc is coupled to the source of the high reference potential Vcc. The third conductive pad P_Row is coupled to the row electrode 18j and receives the selection signal Cornj. The fourth conductive pad P_Col is coupled to the column electrode 20j and receives the data signal Dataj. The dimensions of the conductive pads P_Gnd, P_Vcc, P_Col, P_Row and the arrangement of the conductive pads P_Gnd, P_Vcc, P_Col, P_Row on the surface 34 are imposed in particular by the design rules of the display pixel 12;j and by the assembly process of the display pixels 1¾ in the display screen 10.

[0050] In one embodiment, the display pixel 1¾ comprises a first display sub-pixel emitting light at a first wavelength, a second display sub-pixel emitting light at a second wavelength, and a third display sub-pixel emitting light at a third wavelength. In one embodiment, the first wavelength corresponds to blue light and is between 430 nm and 490 nm. The first display sub-pixel is then called the blue display sub-pixel. In one embodiment, the second wavelength corresponds to green light and is between 510 nm and 570 nm. The second display sub-pixel is then called the green display sub-pixel. In one embodiment, the third wavelength corresponds to red light and is between 600 nm and 720 nm. The third display sub-pixel is then called the red display sub-pixel.

[0051] Figure 3 shows a functional diagram of an embodiment of display pixel 1¾ of the display screen 10. For a color display screen, display pixel 1¾ comprises at least three display sub-pixels SPix_R, SPix_G, SPix_B emitting radiation of different colors. For example, display sub-pixel SPix_B corresponds to the blue display sub-pixel defined previously, display sub-pixel SPix_G corresponds to the green display sub-pixel defined previously, and display sub-pixel SPix_R corresponds to the red display sub-pixel defined previously. Each sub-pixel SPix_R, SPix_G, SPix_B comprises at least one light-emitting diode (LED). For each display sub-pixel SPix_R, SPix_G, SPix_B, the LED is coupled in series to a controllable current source CS_R, CS_G, CS_B.In this example, for each LED, the anode of the LED receives the high reference potential Vcc, received at the conductive pin P_Vcc of the display pixel 12ij, and the cathode of the LED is, for example, coupled to one terminal of the controllable current source CS_R, CS_G, CS_B, the other terminal of the controllable current source CS_R, CS_G, CS_B receiving the low reference potential Gnd, received at the conductive pin P_Gnd of the display pixel 1¾. Alternatively, the cathode of the LED receives the low reference potential Gnd and the anode of the LED is coupled to one terminal of the controllable current source CS_R, CS_G, CS_B, the other terminal of the controllable current source CS_R, CS_G, CS_B receiving the high reference potential Vcc.

[0052] The display pixel 1¾ further includes an electronic circuit 40 for controlling the controllable current source CS_R, CS_G, CS_B of each display sub-pixel SPix_R, SPix_G, SPix_B. The electronic circuit 40 can, in particular This includes electronic components such as MOS transistors. It may be desirable to use a reduced supply voltage, less than 4 V, for example on the order of 1 V or 1.8 V, to power the electronic components of circuit 40. This reduced supply voltage corresponds, for example, to the voltage that can be applied across the power terminals of the MOS transistors. For this purpose, the display pixel 1¾ may include a circuit, not shown, for providing a reduced supply voltage Vdd, notably used to power circuit 40, for example from the high reference potential Vcc or the selection signal Com; and from the data signal Dataj.

[0053] The circuit 40 includes an interface circuit 46 (Interface) coupled to the conductive pad P_Col, which receives the Dataj data signal, and to the conductive pad P_Row, which receives the selection signal Com; and configured to supply the Data signals to a storage circuit 48 (Color Data Memory). The storage circuit 48 is configured to store analog or digital color signals R, G, B, depending on the received data signals. The color signals R, G, B represent the color components of the image pixels to be displayed by each display sub-pixel SPix_R, SPix_G, SPix_B.

[0054] The circuit 40 further includes a driver circuit 50 (LED driver) for controlling the controllable current source CS_R, CS_G, CS_B associated with each display sub-pixel SPix_R, SPix_G, SPix_B. The driver circuit 50 (LED driver) is configured to control the controllable current sources CS_R, CS_G, CS_B coupled to the LEDs with analog or digital signals I_red, I_green, and I_blue, obtained from the color signals R, G, and B. In one embodiment, the driver circuit 30 may be a single integrated circuit comprising the circuit 40 for controlling the controllable current source CS_R, CS_G, CS_B of each display sub-pixel SPix_R, SPix_G, SPix_B. More generally, the circuit 40 may consist of several integrated circuits.

[0055] According to one embodiment, a pulse-width modulation control is used to drive the current source CS_B of the blue display subpixel SPix_B, while a linear control is used to drive the current source CS_G of the green display subpixel SPix_G and to drive the current source CS_R of the red display subpixel SPix_R. Therefore, the LED of the blue subpixel SPix_B is powered by current pulses of constant intensity, the duration of the pulses depending on the stored color signal B, while the LED of the green subpixel SPix_G is powered by a current whose intensity varies according to the signal of stored color G and that the LED of the red subpixel SPix_R is powered by a current whose intensity varies according to the stored color signal R.

[0056] The fact that the current intensity through the LED of the blue display subpixel SPix_B is constant is advantageous when it is important to obtain a reduced dispersion of the central wavelength of the radiation emitted by the LED of the blue display subpixel SPix_B during operation. Indeed, the central wavelength of the radiation emitted by the LED generally varies according to the current density through the LED, this variation being significant for three-dimensional radial LEDs. In the present embodiment, since the current density through each elementary LED remains constant regardless of the color signal B, the central wavelength of the radiation emitted by the elementary LEDs does not vary during operation.

[0057] According to one embodiment, each of the red and green display subpixels SPix_G and SPix_R comprises a photoluminescent block covering the light-emitting diode (LED). The photoluminescent block absorbs the radiation emitted by the LED and emits radiation at a center wavelength different from the center wavelength of the radiation emitted by the LED. The linear control for the red and green display subpixels SPix_G and SPix_R can cause a variation in the current density supplied to the LED of the red and green display subpixels SPix_G and SPix_R and, consequently, a variation in the center wavelength of the radiation emitted by the LED of the red and green display subpixels SPix_G and SPix_R.However, a photoluminescent block can emit radiation with a fixed center wavelength, even if the center wavelength of the radiation emitted by the LED exhibits dispersion. Therefore, the center wavelength of the radiation emitted by the photoluminescent block remains fixed even if the center wavelength of the radiation emitted by the LED of the red and green display subpixels SPix_G and SPix_R varies due to the linear control for the red and green display subpixels SPix_G and SPix_R.

[0058] The photoluminescent block may include quantum dots. The light conversion performance of the quantum dots tends to decrease over time as a function of the maximum luminous flux received by the quantum dots. Linear control for the red and green display subpixels SPix_G and SPix_R advantageously allows limiting the luminous flux on the dots Quantum dots differ from pulse-width modulation (PWM) control. Consequently, the quantum dots do not always receive maximum intensity light from LEDs. This enhances the durability of the quantum dots' light conversion performance.

[0059] According to one embodiment, the pulse-width modulation control used to control the CS_B current sources of the blue display subpixel SPix_B is a digital pulse-width modulation control. In this case, the I_blue signal is a binary signal and the B color signal is a digital signal.

[0060] Figure 4 shows a functional diagram of an embodiment of the SPix_B display sub-pixel. The controllable current source CS_B comprises a switch SW in series with an adjustable current source VCS providing a controllable current intensity. The switch SW is controlled by the I_blue signal. The adjustable current source VCS is controlled by a constant bias signal Bias.

[0061] Figure 5 shows a functional diagram of an embodiment of the SPix_R display sub-pixel. The controllable current source CS_R comprises a MOS transistor. The I_red signal corresponds to an analog voltage applied to the gate of the CS_R transistor. The SPix_G display sub-pixel can have the same structure as the SPix_R display sub-pixel.

[0062] According to one embodiment, the data signal Dataj, received on the conductive pad P_Col of each display pixel 12ij, is a binary signal alternating between a low logic state "0" and a high logic state "1", the low logic state corresponding to the low reference potential Gnd and the high logic state "1" corresponding to a low voltage, for example, about 1 V, lower than the reduced supply voltage Vdd. In this embodiment, the stored color signals R, G, and B are digital signals.

[0063] Figure 6 shows a functional diagram of an embodiment of the display pixel 1¾ circuit 40 of Figure 3 when the Dataj signal is a binary signal and the color signals R, G, and B are digital signals. The storage circuit 48 comprises three registers RR, GR, and BR. The bits of the digital color signal R are stored in the memory cells of register RR, the bits of the digital color signal G are stored in the memory cells of register RG, and the bits of the digital color signal B are stored in the memory cells of register RB. The driver circuit 50 includes a digital-to-analog converter DAC_R configured to receive the digital color signal R from register RR and to convert the digital color signal R into an analog signal corresponding to the I_red signal. The driver circuit 50 also includes a converter digital-to-analog DAC_G configured to receive the digital color signal G from the RG register and to convert the digital color signal G into an analog signal corresponding to the I_green signal.

[0064] In another embodiment, the stored color signals R and G are analog signals. The storage circuit 48 may include capacitors configured to store the analog color signals R and G. In one embodiment, the circuit 48 is configured to convert the data bits relating to the color signal R into an analog voltage proportional to the data, the analog voltage being stored in a first capacitor. The voltage across the first capacitor can then correspond to the analog color signal R. The circuit 48 is configured to convert the data bits relating to the color signal G into an analog voltage proportional to the data, the analog voltage being stored across a second capacitor. The voltage across the first capacitor can then correspond to the analog color signal G.

[0065] According to one embodiment, the selection signal Com;, received at the conductive pad P_Row of each display pixel 12ij, is a binary signal alternating between a low logic state "0" and a high logic state "1", the low logic state corresponding to the low reference potential Gnd and the high logic state "1" corresponding to a low voltage, for example, about 1 V, lower than the reduced supply voltage Vdd.

[0066] Figure 7 shows a functional diagram of another embodiment of the display pixel 12^ of the display screen 10. The display pixel 12^ shown in Figure 7 comprises all the elements of the display pixel 12ij shown in Figure 6. The interface circuit 46 is configured to provide a clock signal Clk from the selection signal Com; or from the data signal Dataj and a data signal Data from the data signal Dataj to the storage circuit 48 in a first phase P1, also called the programming phase, and to provide a PWM modulation signal from the selection signal Com; to the driver circuit 50 to control the controllable current source CS_B of the display sub-pixel SPix_B in a second phase P2, also called the display phase. The PWM modulation signal can be equal to the selection signal Com; during each display phase P2.The clock signal Clk can be equal to the selection signal Com; during each PI programming phase when it is generated from the selection signal Com; . The storage circuit 48 is configured, when clocked by the clock signal Clk, to store the digital color signals R, G, B from the received digital data.

[0067] Fig. 8 represents a time diagram of signals received by the display pixels 1¾ having the structure shown in Fig. 7 for an embodiment of a method for displaying an image on the display screen 10.

[0068] The potentials Vcc and Gnd are substantially constant. The pixels of a new image to be displayed are displayed successively from row 1 to row M. The frame duration T is defined as the time separating two successive selections of the same row of the display screen 10. The timing diagrams of the Comi and Datai signals will be detailed for row 1, given that the timing diagrams of the Comi signals are similar to the timing diagram of the Comi signal, although shifted in time. The display of a new image pixel by a display pixel 12ij, with j varying from 1 to N, in row 1 comprises a first phase PI followed by a second phase P2. During the PI phase, the Datai signals are transmitted to each display pixel 12i of row 1, with only the Datai signal being shown in [Fig. 8].During the second phase P2, the light-emitting diodes of each display pixel 12ij are controlled from the color signals R, G, B, determined from the data signals Data,. .

[0069] During the first PI phase, the selection signal Comi is set to state "1". The Comi signal remaining in state "1" for an extended period is detected by the interface circuit 46 for each display pixel 12ij in row 1, thus enabling the selection of the display pixels 12ij in that row, while the display pixels in the other rows remain unselected. During the first PI phase, the data signals Dataj are transmitted to the column electrodes 20j. For each display pixel 12ij, the interface circuit 46 determines a clock signal Clk and data Data from the pulses of the data signal Dataj. For example, each pulse of the Dataj signal may have a first duration or a second duration, longer than the first.The Clk signal can correspond to a sequence of pulses of the same duration whose rising edges coincide, with a possible constant offset, with the rising edges of the pulses of the Dataj signal. The Data can correspond to a binary signal in the state "0" when the Dataj signal pulse has the first duration, and in the state "1" when the Dataj signal pulse has the second duration. The interface circuit 46, selected by the Comi signal in the state "1", delivers, at the rate of the clock signal Clk, the Data which is stored in the circuit 48 as digital signals R, G, B whose bits are provided by the successive values ​​of the Data signal. The end of the first PI period for one row corresponds to the beginning of the first PI period for the next row.

[0070] According to one embodiment, the light-emitting diodes of the display sub-pixel SPix_B are controlled by pulse-width modulation or PWM. For this purpose, during the second phase P2, the selection signal Comi presents the repetition of a succession of pulses in the "1" state which are transmitted by the interface circuit 46 of each display pixel 12ij of row 1 to the circuit 50 (PWM signal) to time the operation of the circuit 50 for the control of the LEDs of the display sub-pixel SPix_B by pulse-width modulation. The number of pulses in the succession corresponds to the number of bits of each digital signal B. By way of example, when the current source CS_B is as shown in [Fig.[4] The SW switch is opened or closed, according to the PWM pulses, depending on the value "0" or "1" of each bit of the color signal B, starting with the most significant bit. This transistor is kept on or off until the next pulse of the Comi signal. The time between two successive pulses of the Comi signal is halved each time, so that the total time the LED is on depends on the value of the color signal B. The sequence of pulses of the Com i signal is repeated until the next first PI phase of the rank 1 row, a single repetition being illustrated as an example in [Fig. 8].

[0071] According to another embodiment, the data signal Dataj, received on the conductive pad P_Col of each display pixel 12ij, is an analog signal. The storage circuit 48 may include capacitors configured to store the analog color signals R, G, B.

[0072] Figure 9 shows a functional diagram of another embodiment of the display pixel 1¾ of the display screen 10. The display pixel 1¾ shown in Figure 9 comprises all the elements of the display pixel 1¾ shown in Figure 6. According to one embodiment, the selection signal Com;, received on the conductive pads P_Row of each display pixel 1¾, is an analog signal. The interface circuit 46 is configured to receive the data signal Dataj and to provide the analog signal Data to the storage circuit 48 in the programming phase P1 and to provide an analog reference signal REF suitable for executing a PWM command in the display phase P2. The storage circuit 48 includes a capacitor CR for storing the analog color signal R. The analog color signal R can correspond to the voltage across capacitor CR. The storage circuit 48 includes a capacitor CG for storing the analog color signal G.The analog color signal G can correspond to the voltage across capacitor CG. The storage circuit 48 includes a capacitor CB to store the analog color signal B. The analog color signal B can correspond to the... voltage across capacitor CB. The control circuit 50 is configured to control the controllable current sources CS_R, CS_G, CS_B coupled to the LEDs with control signals obtained from the analog control signals R, G, B and, for the current source CS_B of the display sub-pixel SPix_B, from the analog reference signal REF.

[0073] In one embodiment, the Com signal allows both the selection of the display pixel 1¾ for the storage of a Data signal and the provision of the analog reference signal used for the PWM control of the light-emitting diodes of the display sub-pixel SPix_B.

[0074] Fig. 10 represents time diagrams of signals received by the display pixels 1¾ for an embodiment of a method of displaying an image on the display screen 10. For illustrative purposes, in Fig. 10, only signals associated with the first row and the first column of the display screen 10 have been represented.

[0075] In the present embodiment, the potentials Vcc and Gnd, not shown in [Fig. 10], are substantially constant during the operation of the display screen 10. The pixels of a new image to be displayed are displayed successively from row 1 to row M. The frame duration T is defined as the time separating two successive selections of the same row of the display screen 10. The display of a new image pixel by a display pixel 12ij, j ranging from 1 to N, in row i comprises a first phase PI followed by a second phase P2. During the PI phase, analog data signals Dataj are transmitted to the display pixels 12ij of row i, only the Datai signal being shown in [Fig. 10]. Each display pixel 12ij stores a new value of the analog color signal R, G, or B from the received analog data signal Dataj.According to one embodiment, the display pixel 1¾ can receive the Dataj data signals corresponding to the different colours successively during the PL phase. During the second phase P2, the light-emitting diodes of each display pixel 12i j are controlled from the stored colour signals R, G, B.

[0076] During the first PI phase, the selection signal Com; is set to a substantially constant high level, thus forming a voltage pulse. The pulse of the Com; signal is detected by the interface circuit 46 of each display pixel 1¾ of the row of rank i and thus allows the display pixels 1¾ of this row to be selected, while the display pixels of the other rows are not selected. In one embodiment, the duration of each pulse is less than the frame duration divided by the number of rows to be selected, preferably less than 100 ps. During the first PI phase, the data signals Dataj are transmitted to the column electrodes 20j. Each Dataj signal can correspond to an analog signal capable of taking a constant value ranging from a minimum to a maximum value. The interface circuit 46 delivers the Dataj signal, which is stored in the circuit 50 of the display pixel 12ij as an R, G, or B signal whose value depends on the Dataj signal, the Ru signal stored by the display pixel 12i, and the current I, Rni flowing through the LED of the sub-display pixel SPix_B of the display pixel 12i4, shown as an example in [Fig. 10]. The end of the first PI phase for one row can correspond to the beginning of the first PI phase for the next row.

[0077] According to one embodiment, the LEDs of the display subpixel SPix_B of the display pixel 12ij are controlled by pulse-width modulation. To this end, during a first portion P2_ON of the second phase P2, the selection signal Com; varies periodically, exhibiting a succession of identical patterns that are detected by the interface circuit 46 of each display pixel 1¾ of the row of rank i. The interface circuit 46 transmits the sequence of patterns to the circuit 50, as an analog reference signal REF for controlling the LEDs of the display subpixel SPix_B by pulse-width modulation. By way of example, in [Fig. 10], each pattern comprises a rising voltage ramp followed by a falling voltage ramp. According to another example, each pattern comprises only a rising voltage ramp or only a falling voltage ramp.In general, each pattern comprises a specific voltage variation curve, for example, an exponential growth curve, a sinusoidal curve, etc. The shape of the pattern may, for example, include compensations for ocular sensitivity, in particular a gamma correction. The repetition frequency of the pattern on each P2_OFF phase allows for between 1 and 1,000 pattern cycles per P2_OFF phase.

[0078] The circuit 50 of the display pixel 1¾ controls the LEDs of the display sub-pixel SPix_B based on the comparison between the stored analog signal B and the analog reference signal REF. For example, the current source CS_B of the display sub-pixel SPix_B is deactivated when the stored analog signal B is greater than the analog reference signal REF, resulting in a zero current I, pn supplying the LED, and the current source CS_B of the display sub-pixel SPix_B is activated when the stored analog signal B is less than the analog reference signal REF, resulting in a non-zero constant current L, pp u supplying the LED.

[0079] During a second P2_OFF portion of the second P2 phase, the selection signal Com; is maintained at a constant level, for example, at a low level, so that the LEDs of the SPix_B display subpixels of the row display pixels are turned off. The duration of the second P2_OFF portion can vary from 0 to 100% of the duration of the second P2 phase. In particular, the second P2_OFF portion may be absent. According to one embodiment, the duration of each P2 phase is equal to the duration of the Tframe minus the duration of the P1 phase.

[0080] During the display phase P2, the control circuit 50 controls the controllable current sources CS_R and CS_G coupled to the LED light-emitting diodes of the display sub-pixels SPix_R and SPix_B with the control signals I_green and I_red obtained which can correspond to the analog control signals R and G.

[0081] According to another embodiment, the data signal Dataj, received on the conductive pad P_Col of each display pixel 12^, is a digital signal for transmitting the color signal B and an analog signal for transmitting the color signals G and R. Therefore, the color signal B is a digital signal, and the storage circuit 48 may include a register for storing the digital color signal B. Furthermore, the color signals R and G are each an analog signal. The storage circuit 48 may include capacitors configured to store the analog color signals R and G.

[0082] Figure 11 is a simplified partial cross-sectional view of an embodiment of the display pixel 1¾ comprising microwires or nanowires. The display pixel 12jj comprises, from bottom to top in Figure 11: - a substrate 60 comprising opposite surfaces 62 and 64, the upper surface 62 being preferably flat at least at the level of the light-emitting diodes; - a germination layer 66 made of a material promoting the growth of the threads and arranged on the surface 62; - an insulating layer 68 covering the germination layer 66 and comprising openings 70 exposing parts of the germination layer 66; - LED light-emitting diodes (six LEDs are shown), each LED being in contact with the germination layer 66 through one of the openings 70; - an insulating layer 74 extending over the side walls of a lower part of the LED and extending over the insulating layer 68 between the LEDs; - a layer 76 forming an electrode covering each LED and extending over the insulating layer 74 between the LEDs; - a reflective conductive layer 78 extending over the insulating layer 68 between the light-emitting diodes LEDs; - a reflective conductive layer 78, extending over the layer 76 between the LED light-emitting diodes, the conductive layer 78 being alternatively interposed between the electrode layer 76 and the insulating layer 74 between the LED light-emitting diodes; - a dielectric protection layer 80 extending over layers 76 and 78; - 82 photoluminescent blocks covering the light-emitting diode assemblies of the SPix_R and SPix_G display sub-pixels; - blocks 84 transparent to the radiation emitted by the light-emitting diodes of the SPix_B display sub-pixels, these transparent blocks 84 being able to be omitted; - walls 88 between blocks 82, 84, each wall 88 being opaque to the radiation emitted by the LED light-emitting diodes; and - one, two or three color filters 90, for example a single yellow filter, two filters, the first being a yellow filter and the second a red filter, or three filters, the first being a red filter, the second a green filter and the third a blue filter, covering at least part of blocks 82, 84, a single filter 90 covering two blocks being shown as an example.

[0083] According to one embodiment, each light-emitting diode can be a three-dimensional light-emitting diode. According to one embodiment, the LEDs comprise semiconductor layers made of III-V compounds, for example GaN, AIN, InN, InGaN, AlGaN or AlInGaN, or of ILVI compounds.

[0084] A three-dimensional light-emitting diode (LED) comprises a three-dimensional semiconductor element, for example, a wire, a conical, frustoconical, or pyramidal element, in particular a microwire or a nanowire, over which the active area of ​​the LED extends. The term "microwire" or "nanofil" refers to a three-dimensional structure elongated in a preferred direction, of which at least two dimensions, called minor dimensions, are between 5 nm and 2.5 µm, preferably between 50 nm and 2.5 µm, the third dimension, called major dimension, being at least equal to 1 times, preferably at least twice, the largest of the minor dimensions. In some embodiments, the minor dimensions may be less than or equal to about 3 µm, preferably between 100 nm and 3 µm, more preferably between 1 µm and 1.5 µm.In some embodiments, the height of each microwire or nanowire may be greater than or equal to 500 nm, preferably between 1 µm and 50 µm.

[0085] Figure 12 is a partial, schematic cross-sectional view of an embodiment of the LEDs of the display pixel 12. According to one embodiment, each LED comprises a wire 90 in contact with the seed layer 66 through one of the openings 70 and an envelope 92 comprising a stack of semiconductor layers covering the side walls and the top of the wire 90. Such a configuration is said to be radial. The assembly formed by each wire 90 and the associated envelope 92 constitutes the LED.

[0086] The casing 92 may comprise a stack of several layers, including in particular an active layer 94 and a bonding layer 96. The active layer 94 is the layer from which the majority, and preferably all, of the radiation emitted by the light-emitting diode (LED) originates. By way of example, the active layer 94 may include confinement means, such as a single quantum well or multiple quantum wells. The bonding layer 96 may comprise a stack of semiconductor layers of the same IILV material as the wire 90, but with a conductivity type opposite to that of the wire 90.

[0087] [Fig. 13] is a partial and schematic cross-sectional view of another embodiment of the LED of the display pixel 1¾. The LED shown in [Fig. 13] comprises all the elements of the LED shown in [Fig. 12], except that the envelope 92 is present only at the top of the wire 90. Such a configuration is said to be axial.

[0088] The formation of the LED light-emitting diodes as shown in Figures 12 and 13, i.e. the growth of the wires 90 in the openings 70, and the formation of the envelopes 92 covering the wires 90 can be carried out for example by metal-organic vapor deposition (MOCVD) or by any other suitable process.

[0089] The substrate 60 can correspond to the control circuit 30 described previously.

[0090] The germination layer 66 is made of a material that promotes the growth of the fibers. For example, the material forming the germination layer 66 may be a nitride, carbide, or boride of a transition metal from group IV, V, or VI of the periodic table of elements, or a combination of these compounds. In one embodiment, the germination layer 66 may be omitted. In another embodiment, the germination layer 66 may be replaced by germination pads, for example, formed at the bottom of the openings 70.

[0091] Each insulating layer 68, 74, 80 can be made of a dielectric material, for example silicon dioxide (SiO2), silicon nitride (SixNy, where x is approximately equal to 3 and y is approximately equal to 4, for example Si3N4), oxynitride of silicon (in particular of general formula SiOxNy, for example Si2ON2), aluminum oxide (Al2O3), hafnium oxide (HfO2), titanium dioxide (TiO2), or diamond. The insulating layer 68, 74, 80 may have a single-layer structure or correspond to a stack of two or more layers. When the insulating layer 68 corresponds to a stack of at least two layers, the top layer of the stack is insulating, for example, made of a dielectric material.

[0092] The conductive layer 78 preferably corresponds to a metallic layer, for example aluminium, silver, copper, gold or zinc. The thickness of the conductive layer 78 can be between 0.01 pm and 1000 pm.

[0093] The electrode layer 76 is capable of transmitting the electromagnetic radiation emitted by the light-emitting diodes. The material forming the electrode layer 76 can be a transparent and conductive material such as indium tin oxide (ITO), aluminum or gallium-zinc oxide, or graphene. The thickness of the electrode layer 76 can be between 0.01 µm and 10 µm.

[0094] According to one embodiment, each photoluminescent block 82 is located opposite one or a set of light-emitting diodes. Each photoluminescent block 82 comprises phosphors capable, when excited by the light emitted by the associated LED, of emitting light at a wavelength different from the wavelength of the light emitted by the associated LED. According to one embodiment, the display pixel 1¾ comprises at least two types of photoluminescent blocks 82. Each photoluminescent block 82 of the first type is capable of converting the radiation supplied by the LEDs into a first radiation at a first wavelength, and each photoluminescent block 82 of the second type is capable of converting the radiation supplied by the LEDs it covers into a second radiation at a second wavelength.

[0095] In one embodiment, the light-emitting diodes are capable of emitting blue light, that is, radiation with a wavelength between 430 nm and 480 nm. In another embodiment, the first wavelength corresponds to green light and is between 510 nm and 570 nm. In yet another embodiment, the second wavelength corresponds to red light and is between 600 nm and 720 nm.

[0096] The aspect ratio of the blocks 82, that is to say the ratio between the height and the maximum width of the block, can be between 0.01 and 10, preferably between 0.05 and 2.

[0097] According to one embodiment, each photoluminescent block 82 comprises particles of at least one photoluminescent material, for example in a transparent matrix. An example of a photoluminescent material is yttrium aluminum garnet. (YAG) activated by the trivalent cerium ion, also called YAG:Ce or YAG:Ce3+. The average particle size of conventional photoluminescent materials is generally greater than 5 pm.

[0098] According to one embodiment, each photoluminescent block 82 comprises a matrix in which nanometer-sized single-crystal particles of a semiconductor material are dispersed, also referred to as semiconductor nanocrystals or luminescent nanoparticles in the remainder of this document. The internal quantum efficiency QYint of a photoluminescent material is equal to the ratio of the number of photons emitted to the number of photons absorbed by the photoluminescent substance. The internal quantum efficiency QYint of semiconductor nanocrystals is greater than 5%, preferably greater than 10%, and more preferably greater than 20%.

[0099] According to one embodiment, the average size of the nanocrystals is between 0.5 nm and 1000 nm, preferably between 0.5 nm and 500 nm, more preferably between 1 nm and 100 nm, and in particular between 2 nm and 30 nm. For dimensions smaller than 50 nm, the photoconversion properties of the semiconductor nanocrystals depend essentially on quantum confinement phenomena. The semiconductor nanocrystals then correspond to quantum dots.

[0100] According to one embodiment, the semiconductor material of the semiconductor crystals is selected from the group comprising cadmium selenide (CdSe), indium phosphide (InP), cadmium sulfide (CdS), zinc sulfide (ZnS), zinc selenide (ZnSe), cadmium telluride (CdTe), zinc telluride (ZnTe), cadmium oxide (CdO), cadmium zinc oxide (ZnCdO), cadmium zinc sulfide (CdZnS), cadmium zinc selenide (CdZnSe), indium silver sulfide (AgInS2), PbScX3 type perovskites where X is a halogen atom, in particular iodine (I), bromine (Br), or chlorine (Cl), and a mixture of at least two of these compounds. According to one embodiment, the semiconductor material of the semiconductor nanocrystals is chosen from the materials mentioned in the publication by Le Blevenec et al. in Physica Status Solidi (RRL) - Rapid Research Letters Volume 8, No. 4, pages 349-352, April 2014.

[0101] According to one embodiment, the dimensions of the semiconductor nanocrystals are selected according to the desired wavelength of the radiation emitted by the semiconductor nanocrystals. For example, CdSe nanocrystals with an average size of approximately 3.6 nm are capable of converting blue light into red light, and CdSe nanocrystals with an average size of approximately 1.3 nm are capable of converting blue light into green light. According to another embodiment, the composition of the semiconductor nanocrystals is chosen by function of the desired wavelength of the radiation emitted by the semiconductor nanocrystals.

[0102] The matrix is ​​at least partially transparent to the radiation emitted by photoluminescent particles and / or LEDs, preferably more than 80%. The matrix is, for example, made of silica. The matrix is, for example, made of any at least partially transparent polymer, in particular silicone, acrylic resin, or poly(methyl methacrylate) (PMMA) or polylactic acid (PLA) resin. The matrix may, in particular, be made of a polymer that is at least partially transparent and used with 3D printers. The matrix may be a photosensitive or non-photosensitive glass deposited by spin-on glass (SOG). In one embodiment, the matrix contains from 2% to 90%, preferably from 10% to 60% by weight, of nanocrystals, for example, about 30% by weight of nanocrystals.

[0103] The thickness of the photoluminescent blocks 82 depends on the concentration of nanocrystals and the type of nanocrystals used. The height of the photoluminescent blocks 82 is preferably greater than the height of the wires 71 and less than or equal to the height of the walls 88. In top view, each photoluminescent block 82 can correspond to a square, a rectangle, an "L"-shaped polygon, etc., having an area that can be equal to the area of ​​a square having a side length of 1 pm to 100 pm, preferably from 3 pm to 15 pm.

[0104] According to one embodiment, the opaque walls 88 are reflective for the radiation emitted by the light-emitting diodes (LEDs). The walls 88 are at least partially made of at least one reflective material. The reflective material may be a metallic material, in particular iron, copper, aluminum, tungsten, silver titanium, hafnium, zirconium, or a combination of at least two of these compounds. Preferably, the walls 88 are made of a material compatible with the manufacturing processes used in microelectronics. Preferably, the walls 88 are made of aluminum or silver.

[0105] The height of the walls 88, measured along a direction perpendicular to the surface 62, is between 300 nm and 200 pm, preferably between 3 pm and 15 pm. The thickness of the walls 88, measured along a direction parallel to the surface 62, is between 100 nm and 50 pm, preferably between 0.5 pm and 10 pm.

[0106] According to one embodiment, the walls 88 may be made of a reflective material or coated with a reflective material at the wavelength of the radiation emitted by the photoluminescent blocks 82 and / or the light-emitting diodes. Preferably, the walls 88 surround the photoluminescent blocks 82. The walls 88 then reduce crosstalk between adjacent photoluminescent blocks 82.

[0107] Various embodiments and variants have been described. Those familiar with the subject matter will understand that certain features of these various embodiments and variants can be combined, and that other variants will present themselves to those familiar with the subject matter.

[0108] Finally, the practical implementation of the described embodiments and their variants is within the reach of competent persons in the field, based on the functional indications given above.

Claims

Demands

1. Display pixel (1¾) comprising at least first and second light-emitting diodes (LEDs), a first controllable current source (CS_B) supplying said first light-emitting diode (LED) with a first current, a second controllable current source (CS_R) supplying said second light-emitting diode (LED) with a second current, and an electronic circuit (40) comprising a storage circuit (48) for storing at least first and second color signals (R, B) and a driver circuit (50) configured to control the first controllable current source (CS_B) to supply the first current by pulse-width modulation from the first color signal (B) and configured to control the second controllable current source (CS_R) to supply the second current by linear control from the second color signal (R),in which the second light-emitting diode (LED) is covered by a first photoluminescent block (82).

2. Display pixel according to claim 1, further comprising a third light-emitting diode (LED) and a third controllable current source (CS_G) supplying said third light-emitting diode (LED) with a third current, the storage circuit (48) being configured to store a third color signal (G) and the driver circuit (50) being configured to control the third controllable current source (CS_G) to supply the third current by a linear control based on the third color signal (G).

3. Display pixel according to claim 1 or 2, wherein the first color signal (B) is a digital signal and the storage circuit (48) includes first memory cells (RB) for storing the bits of the first color signal (B).

4. Display pixel according to any one of claims 1 to 3, wherein the second color signal (R) is a digital signal and the storage circuit (48) includes second memory cells (RR) for storing the bits of the second color signal (R).

5. Display pixel according to claim 4, wherein the driver circuit (50) comprises a digital-to-analog converter (DAC_R) configured to convert the second color signal (R) stored in the second memory cells (RR) into an analog control signal (I_red) to control the second current source (CS_R).

6. Display pixel according to claim 1 or 2, wherein the first color signal (B) is an analog signal and the storage circuit (48) includes a first capacitor (CB) for storing the first color signal (B).

7. Display pixel according to claim 1 or 2, wherein the second color signal (R) is an analog signal and the storage circuit (48) includes a second capacitor (CR) for storing the second color signal (B).

8. Display pixel according to any one of claims 1 to 7, wherein each of the first and second light-emitting diodes (LEDs) comprises several elementary light-emitting diodes each comprising an active area (94) covering a three-dimensional semiconductor element (90) corresponding to a wire, conical, frustoconical or pyramidal element on the order of a nanometer or micrometer.

9. Display pixel according to any one of claims 1 to 8, wherein the first light-emitting diode (LED) is configured to emit a first radiation at a first wavelength, wherein the second light-emitting diode (LED) is configured to emit a second radiation at a second wavelength, and wherein the first photoluminescent block (82) is configured to convert the second radiation into a third radiation at a third wavelength, different from the second wavelength.

10. Display pixel according to claim 9, wherein the first wavelength is equal to the second wavelength within 10%.

11. Display pixel according to any one of claims 1 to 10, wherein the first photoluminescent block (82) comprises first quantum dots.

12. Display pixel according to claim 2, wherein the third light-emitting diode (LED) is covered by a second photoluminescent block (82).

13. Display pixel according to claims 9 and 12, wherein the third light-emitting diode (LED) is configured to emit a fourth radiation at a fourth wavelength, and wherein the second photoluminescent block (82) is configured to convert the fourth radiation into a fifth radiation at a fifth wavelength, different from the fourth wavelength.

14. Display pixel according to claim 13, wherein the fourth wavelength is equal to the first wavelength within 10%.

15. Display pixel according to any one of claims 12 to 14, wherein the second photoluminescent block (82) comprises second quantum dots.

16. Display pixel according to any one of claims 1 to 15, comprising a single integrated circuit (30) including said electronic circuit (40) comprising said storage circuit (48) and said driver circuit (50).

17. Display pixel according to claim 16, comprising an optoelectronic circuit (32) fixed to the integrated circuit (30), said optoelectronic circuit (32) comprising the first and second light-emitting diodes (LEDs).

18. Display screen (10) comprising display pixels (1¾) according to any one of claims 1 to 17; first electrodes (180) coupled to the drive circuits (50) of the display pixels (1¾); a first circuit (22) for providing a selection signal (Com;) on each first electrode for selecting the display pixels (1¾) coupled to the first electrode; second electrodes (20j) coupled to the electronic circuits (40) of the display pixels (1¾); and a second circuit (24) for providing data signals (Dataj) on the second electrodes.

19. Display screen according to claim 18, wherein the second circuit (24) is configured to provide the data signals (Dataj) on the second electrodes (20j) in the form of analog signals.

20. Display screen according to claim 18, wherein the second circuit (24) is configured to provide the data signals (Dataj) on the second electrodes (20j) in the form of digital signals. 29

21. Display screen according to claim 18, wherein the second circuit (24) is configured to provide data signals (Data j) on the second electrodes (20j) comprising an alternation of digital and analog signals.

Images