Two-Dimensional Nanocrystal Assemblies for Photocapacitive Devices

• Published in: ACS applied electronic materials Vol. 5; no. 3; pp. 1770 - 1777
• Main Authors: Mahadevu, Rekha, Pandit, Triloki, Samuel, Jibin J., Ghosh, Uddipan, Jana, Biman, Gupta, Hridesh Kumar, Aetukuri, Nagaphani, Pandey, Anshu
• Format: Journal Article
• Language: English
• Published: American Chemical Society 28.03.2023
• Subjects: quantum dots; assemblies; 2D; negative capacitance; nanocrystals; photodetector
• ISSN: 2637-6113; 2637-6113
• DOI: 10.1021/acsaelm.2c01785

We describe the emergence of photocapacitance in two-dimensional layered nanocrystal assemblies. Devices are electrically probed by the application of a lateral bias across interdigitated electrodes. We observe capacitive current–voltage characteristics that are individually absent in the nanocrystals. Besides the occurrence of a large zero-bias capacitance, the assemblies further show a transient negative capacitive behavior where the small signal capacitance is found to attain values over a ±100 nF range. We show that this system behaves as a damped anharmonic oscillator. Further, the bias dependence of capacitance, characteristics under asymmetric cycling, as well as its relationship with shunt resistance are consistent with the system attaining a transient negative capacitance while migrating around a single energy minimum. We show modulation of the capacitive behavior by incident light enabling the usage of these materials in a photocapacitive detector device.