Patent ID: 8373359

Claim:
A light-emitting device, comprising: an emitting layer including a solution containing an emitting material and a solvent; first and second electrodes in contact with the solution; a voltage-supply circuit applying an operating voltage between the first and second electrodes; an ammeter measuring an amount of electric current flowing between the first and second electrodes; and a controller controlling an operation of the voltage-supply circuit such that a polarity of the operating voltage reverses and determining a timing of reversing the polarity based on an output of the ammeter, wherein a part of the emitting material is present as a first cation that is soluble in the solvent, and another part of the emitting material is present as a second cation that is a reduction product of the first cation and soluble in the solvent, a reduction product of the second cation being insoluble or low-soluble in the solvent, and wherein the first and second electrodes are arranged on back and front sides of the emitting layer, respectively, and the controller controls the operation of the voltage-supply circuit in a case where the electric potential of the first electrode is lower than the electric potential of the second electrode such that the polarity reverses when an absolute value of the amount of the electric current falls below a first criteria value and controls the operation of the voltage-supply circuit in a case where the electric potential of the first electrode is higher than the electric potential of the second electrode such that the polarity reverses when an absolute value of the amount of the electric current falls below a second criteria value, the second criteria value being greater than the first criteria value.