Characterization of two-step photon absorption current in ZnTeO-based intermediate band solar cell

Abstract Two-step photon absorption (TSPA) currents in ZnTeO-based intermediate band solar cell (IBSC) have been investigated experimentally in detail using a red and an infrared laser with wavelengths of 662 nm and 1306 nm as the excitation lights from VB to IB (VB→IB) and from IB to CB (IB→CB), respectively. From the red laser irradiation density dependence of photocurrent, the existence of two current paths is demonstrated. Temperature dependences of photocurrent and TSPA current have revealed the increase of TSPA at <50 K and 100–150 K due to the decrease of direct escape current through the blocking layer and increased electron concentration in IB by Cl donor activation, respectively. This study demonstrates experimentally the importance of the suppression of direct escape of electrons from IB for further improvement.