Solar diode sensor: Sensing mechanism and applications

A Highly Selective and Self‐Powered Gas Sensor Via Organic Surface Functionalization of p‐Si/n‐ZnO Diodes

“…Under illumination with solar light (AM1. 5), an open circuit voltage (Voc) is induced by the build-in potential at the p-n heterojunction [2,13,14] that is used as a self-generated signal for the sensor. To ensure a strong and measurable Voc signal even under low illumination conditions, every device contained several diodes connected in series by evaporated gold contacts (9, 16 or 26 diodes; see Figure 1c).…”

“…The fact that no response towards NO2 was observed for devices without SAM modification further indicates that the gas-sensor interaction is solely subsiding by gas-SAM interactions in case of modified samples (see Figure S6), as the incident light (out of the UV range) is not activating direct interaction between ZnO and the surrounding gas atmosphere. [2] Since the illumination with light in the visible range (e.g. natural sunlight) is sufficient to facilitate gas desorption processes for fast response and recovery processes of SAM modified gas sensors, [7] the organic groups furthermore ensure a sensing operation without the need of external thermal or UV light energy that is usually required for the activation of the inorganic surface of traditional gas sensor systems and consume a major fraction of the total required energy in conventional sensor systems.…”

“…To ensure a strong and measurable Voc signal even under low illumination conditions, every device contained several diodes connected in series by evaporated gold contacts (9, 16 or 26 diodes; see Figure 1c). This configuration resulted in a linear increase of the measured Voc signal proportional with the number of diodes in series under light, with an average contribution of Voc,exp = 72 ± 6 mV/diode (typical value for p-Si/n-ZnO diodes) [2] and leads to measured values of 0.65 V (9 diodes), 1.35 V (16 diodes) and 1.84 V (26 diodes) respectively (see Figure 1c and Figure S2 in supporting information). Figure 1d shows the band diagram of the Au/p-Si/n-ZnO/Au system in equilibrium (see supporting information for further details).…”

“…Recent works have shown promising concepts to realize selfpowered gas sensors that are capable of detecting gases without the need of external power sources to Submitted to 2 activate the sensor-gas interaction or to actively generate a read out signal. [2,3] These sensors drastically reduce power consumption compared to conventional semiconductor gas sensors and additionally reduce the required space for integration. All these attempts so far were based on purely nano structured inorganic metal oxide sensor materials that provide a good sensitivity towards different gases due to their high surface-to-volume ratio.…”

“…[2,3] These sensors drastically reduce power consumption compared to conventional semiconductor gas sensors and additionally reduce the required space for integration. All these attempts so far were based on purely nano structured inorganic metal oxide sensor materials that provide a good sensitivity towards different gases due to their high surface-to-volume ratio.…”