Wafer-Scale, Thickness-Controlled <i>p</i>‑CuInSe₂/n-Si Heterojunction for Self-Biased, Highly Sensitive, and Broadband Photodetectors

The fabrication of wafer-scale, ultrathin, and highly sensitive p-CuInSe2/n-Si heterojunction photodetectors is demonstrated. CuInSe2 has been extensively utilized for photovoltaic applications owing to its excellent optoelectronic properties. Although the wafer-scale CuInSe2 photodetector fabrication and device-level demonstration are not well explored, it is of utmost importance to unveil the beneficial aspects of CuInSe2 by fabricating its wafer-scale heterojunction photodetectors. The wafer-scale CuInSe2 photodetectors are still underway, and the possible light management mechanism for various CuInSe2 thicknesses is underexplored. As a result, it is demanded to discover minimum and optimum CuInSe2 thickness for highly efficient wafer-scale photodetection. To serve this purpose, a strategy is projected to greatly increase the photodetection performance, possessing excellent sensitivity, broad spectral responsivity, and stability along with high speed. Our understanding demonstrates the capability to control the thickness parameter (from 436 to 43 nm) and alter the structural, optical, chemical, and optoelectronic characteristics of the p-CuInSe2 semiconductors in an unprecedented manner to attain the desired characteristics of photodetection performance. The maximum sensitivity, detectivity, and LDR, that is, 3.7 × 103, 0.61 × 1011 Jones, and 72 dB, respectively, are obtained under the halogen light for self-biased conditions. The highly efficient NIR response has been attained, and maximum sensitivity, responsivity, detectivity, and LDR, that is, 2.2 × 103, 158 A/W, 1.3 × 1012 Jones, and 79 dB at 980 nm, respectively, are obtained. The present work offers a sustainable approach for the wafer-scale uniform synthesis of ultrathin CuInSe2 (58 nm) for the development of self-biased, highly efficient, and broadband photodetectors

Plasmon Field Effect Transistor for Plasmon to Electric Conversion and Amplification

Direct coupling of electronic excitations of optical energy via plasmon resonances opens the door to improving gain and selectivity in various optoelectronic applications. We report a new device structure and working mechanisms for plasmon resonance energy detection and electric conversion based on a thin film transistor device with a metal nanostructure incorporated in it. This plasmon field effect transistor collects the plasmonically induced hot electrons from the physically isolated metal nanostructures. These hot electrons contribute to the amplification of the drain current. The internal electric field and quantum tunneling effect at the metal–semiconductor junction enable highly efficient hot electron collection and amplification. Combined with the versatility of plasmonic nanostructures in wavelength tunability, this device architecture offers an ultrawide spectral range that can be used in various applications

Ultrawide Spectral Response of CIGS Solar Cells Integrated with Luminescent Down-Shifting Quantum Dots

Conventional Cu­(In_1–<i>x</i>,Ga<i>_x</i>)­Se₂ (CIGS) solar cells exhibit poor spectral response due to parasitic light absorption in the window and buffer layers at the short wavelength range between 300 and 520 nm. In this study, the CdSe/CdZnS core/shell quantum dots (QDs) acting as a luminescent down-shifting (LDS) layer were inserted between the MgF₂ antireflection coating and the window layer of the CIGS solar cell to improve light harvesting in the short wavelength range. The LDS layer absorbs photons in the short wavelength range and re-emits photons in the 609 nm range, which are transmitted through the window and buffer layer and absorbed in the CIGS layer. The average external quantum efficiency in the parasitic light absorption region (300–520 nm) was enhanced by 51%. The resulting short circuit current density of 34.04 mA/cm² and power conversion efficiency of 14.29% of the CIGS solar cell with the CdSe/CdZnS QDs were improved by 4.35 and 3.85%, respectively, compared with those of the conventional solar cells without QDs