Optocoupler comprising a transmitter unit and a receiver unit, wherein the transmitter unit and the receiver unit are electrically isolated from one another and optically coupled together and the two units (S, EM) are integrated in a common housing, and the receiver unit comprises - a number N of part voltage sources connected together in series and constructed as semiconductor diodes, wherein each of the part voltage sources comprises a semiconductor diode (D1, D2, D3, D4, D5) with a p-n transition, and the semiconductor diode (D1, D2, D3, D4, D5) has a p-doped p absorption layer and the semiconductor diode (D1, D2, D3, D4, D5) has an n-doped n absorption layer, characterised in that the n absorption layer is passivated by an n-doped passivation layer with a greater band gap than the band gap of the n absorption layer and the part source voltages of the individual part voltage sources have a difference of less than 20% relative to one another and a tunnel diode (T1, T2, T3, T4) is formed between each two successive part voltage sources, wherein the tunnel diode (T1, T2, T3, T4) comprises several semiconductor layers with a higher band gap than the band gap of the p/n absorption layers and the semiconductor layers with the higher band gap each consist of a material with changed stoichiometry or different element composition relative to the p/n absorption layers of the semiconductor diode (D1, D2, D3, D4, D5) or of a material with changed stoichiometry and different element composition relative to the p/n absorption layers and - the part voltage sources and the tunnel diodes (T1, T2, T3, T4) are monolithically integrated together and together form a first stack with an upper side and a lower side and the number N of the part voltage sources is greater than or equal to three and - at the first stack light is incident at the upper side on the surface of the first stack and the size of the illuminated surface at the stack upper side corresponds substantially or at least with the size of the area of the first stack at the upper side and the first stack has an overall thickness of less than 12 μm, and - at 300 K the first stack has a source voltage of more than 3 volts insofar as the first stack is irradiated with light, and wherein in the direction of light incidence from the upper side of the first stack towards the lower side of the stack the overall thickness of the p and n absorption layers of a semiconductor diode increases from the uppermost diode towards the lowermost diode (D3 - D5) and each p absorption layer of the semiconductor diode (D1, D2, D3, D4) is passivated by a p-doped passivation layer with a greater band gap than the band gap of the p absorption layer and the voltage source in the vicinity of the lower side of the stack has an encircling, projection-shaped edge. - a number N of part voltage sources connected together in series and constructed as semiconductor diodes, wherein each of the part voltage sources comprises a semiconductor diode (D1, D2, D3, D4, D5) with a p-n transition, and the semiconductor diode (D1, D2, D3, D4, D5) has a p-doped p absorption layer and the semiconductor diode (D1, D2, D3, D4, D5) has an n-doped n absorption layer, characterised in that the n absorption layer is passivated by an n-doped passivation layer with a greater band gap than the band gap of the n absorption layer and the part source voltages of the individual part voltage sources have a difference of less than 20% relative to one another and a tunnel diode (T1, T2, T3, T4) is formed between each two successive part voltage sources, wherein the tunnel diode (T1, T2, T3, T4) comprises several semiconductor layers with a higher band gap than the band gap of the p/n absorption layers and the semiconductor layers with the higher band gap each consist of a material with changed stoichiometry or different element composition relative to the p/n absorption layers of the semiconductor diode (D1, D2, D3, D4, D5) or of a material with changed stoichiometry and different element composition relative to the p/n absorption layers and - the part voltage sources and the tunnel diodes (T1, T2, T3, T4) are monolithically integrated together and together form a first stack with an upper side and a lower side and the number N of the part voltage sources is greater than or equal to three and - at the first stack light is incident at the upper side on the surface of the first stack and the size of the illuminated surface at the stack upper side corresponds substantially or at least with the size of the area of the first stack at the upper side and the first stack has an overall thickness of less than 12 μm, and - at 300 K the first stack has a source voltage of more than 3 volts insofar as the first stack is irradiated with light, and wherein in the direction of light incidence from the upper side of the first stack towards the lower side of the stack the overall thickness of the p and n absorption layers of a semiconductor diode increases from the uppermost diode towards the lowermost diode (D3 - D5) and each p absorption layer of the semiconductor diode (D1, D2, D3, D4) is passivated by a p-doped passivation layer with a greater band gap than the band gap of the p absorption layer and