Photoconduction - Hikaridendo (English spelling) photoconduction

Japanese: 光伝導 - ひかりでんどう（英語表記）photoconduction

This is a phenomenon in which electrical conductivity increases when light is shone on a semiconductor or insulator. It is also called the internal photoelectric effect to distinguish it from photoemission. The irradiated light excites electrons in the valence band or impurity level in the sample, generating free electrons and holes, which move within the crystal due to the external electric field, causing an electric current to flow. The magnitude of the photocurrent is proportional to the number of electrons or holes generated by the irradiation and the electric field within a certain range, but it is also related to the lifetime and mobility of the free electrons or holes in the crystal. For example, unlike the case of ohmic contact, where electrons and holes can move without any obstruction at the interface between the sample and the electrode, when the sample is in contact with the electrode through an insulating layer, the photocurrent often does not increase and saturates even if the electric field is strengthened. In general, the saturation current value decreases as the distance between the electrodes decreases. Cadmium sulfide and lead sulfide have strong photoconductivity, and are used in photoconductive (photoconductive) cells to measure light intensity and for camera exposure meters.

Photoconductive

Please see the "Photoconductivity" page.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

半導体や絶縁体に光を当てたとき，電気伝導度が増加する現象で，光電子放射と区別して内部光電効果とも呼ばれる。照射した光が，試料中の価電子帯または不純物準位にある電子を励起して，自由な電子や正孔を生じ，外部から加えた電場によってそれらが結晶中で移動するために電流が流れる。光電流の大きさは，照射によって発生した電子または正孔の数や電場に一定の範囲内で比例するが，結晶中での自由電子または自由正孔の寿命や移動度にも関係する。たとえば，電子や正孔が試料と電極の境界面でなんらの障害も受けずに移動できるオーミックコンタクトの場合と違って，試料が絶縁層を介して電極と接触している場合には電場を強くしても，光電流は増加せずに飽和することが多い。一般に飽和電流値は電極間の距離が小さいほど小さくなる。硫化カドミウムや硫化鉛は光伝導性が強く，光伝導 (光導電) セルの名で光の強度測定やカメラの露出計などに応用されている。