Fabrication of solar cells with CO₂ gas sensing capabilities based on a NiO/ZnO p-n junction for developing self-powered gas sensors

Abstract

Solar cells based on a NiO/ZnO p-n junction structure responding to CO2 gas were fabricated by conventional RF sputtering. The developed NiO/ZnO solar cells exhibited evident photovoltaic effects and response to CO2 gas when exposed to sunlight at room temperature without thermal heating or external power supply. The open-circuit voltage, generated by the solar cells absorbing only UV light, increased in a CO2 atmosphere and decreased in air. Moreover, the response mechanism of the NiO/ZnO solar cells to CO2 gas was investigated using electrochemical impedance spectroscopy. The results suggested that the depletion layer width of the NiO/ZnO interface changed under CO2 gas with light illumination. These results represent the potential application of the NiO/ZnO p-n junction structure toward self-powered gas sensors.

Investigating electrical properties and crystal growth in NiO thin films by spray pyrolysis and electrostatic spray deposition

“…10,11) From a commercial viewpoint, Ni and O are inexpensive and are able to be easily handled as semiconductor materials compared with other wide-bandgap semiconductors. Therefore, NiO is a promising candidate for several applications such as transparent diodes, [12][13][14] UV LEDs, 5) UV detectors, 15) gas sensors, [16][17][18] and visible-light-transparent solar cells. [19][20][21][22] Furthermore, NiO has been investigated as a hole-transport layer in organic solar cells [23][24][25] because its conduction band minimum is close to the vacuum level.…”

“…Dry processes, such as sputtering 5,[18][19][20][21][25][26][27][28] or pulsed laser deposition, 14,15) and wet processes, such as chemical bath deposition, 29,30) mist chemical vapor deposition, 31) and spray pyrolysis, [32][33][34] are well-known methods for NiO thin film deposition. Among these, the spray pyrolysis method has the industrial advantage of enabling large-area deposition because it is simple and easy to use, performs non-vacuum deposition, has a low cost, and allows to easily control the composition ratio and doping.…”

Design and fabrication of poly-Si/SiO2 Fabry–Perot filter for nondispersive IR CO2 sensors

“…1,2) Therefore, developing cost-effective CO 2 sensors has been attracting great interest because of the demand for real-time CO 2 monitoring [3][4][5] at critical CO 2 emission areas. CO 2 detectors can be mainly classified into metal-oxide, 6,7) acoustic, 8,9) catalytic, 10) and optical [11][12][13] sensors. Optical CO 2 sensors are among the most discussed sensor types because of their high sensitivity, selectivity, and long-term stability.…”

Effect of proton irradiation on the sensitivity of CO2 sensors based on SnO2 and SnO–SnO2 heterojunctions

“…Notably, contemporary NDIR CO 2 sensors have lower resistance to proton beams and are difficult to transport to space facilities because of their complex mechanical configuration 9) and heavy weight. More recently, resistive CO 2 sensors based on semiconductor oxides [9][10][11][12][13][14] have been found to offer various advantages, such as high proton resistance, long-term stability, simple device configuration, and low manufacturing costs. Moreover, they are now mounted onto flexible substrates 15,16) to overcome weight concerns.…”