Near infrared photodetectors based on sub‐gap absorption in organohalide perovskite single crystals

Organohalide perovskite optoelectronics based upon large (mm‐sized) single crystals present exciting opportunities for new device platforms and fundamental studies. Herein, we report CH 3 NH 3 PbBr 3 and CH 3 NH 3 PbI 3 single crystals prepared via an inverse temperature crystallization method with strong near infrared photoresponses significantly below the optical gap. Light intensity dependent photocurrent measurements reveal the photoresponse is not a two‐photon phenomenon, but rather is derived from a linear mechanism. The effect (including responsivity and speed) is enhanced in a photoresistor architecture, indicating that the photoresponse is due to absorption into surface trap states in the crystal. Without any optimisation, respectable NIR responsivities at room temperature of ∼10 ‐2 A W −1 at a low 1V bias operating voltage are achieved. These results again demonstrate the remarkable potential of organohalide perovskites as light sensing materials, and the possibilities for engineering a new class of single crystal‐based optoelectronics.