A Pitaya Dye-Sensitized Solar Cell Monitor for Environmental Sunlight Intensity Detection

For measuring environmental sunlight intensity, a novel pitaya dye-sensitized solar cell (DSSC) monitor was utilized in this paper. A pitaya (botanical name: Hylocereus undatus) DSSC sensor and a proposed sensor transducer are consisted together. A linear conversion of environmental sunlight intensity into a frequency output is performed. The novel voltage-to-current conversion technique has digital calibrations to completely eliminate nonlinear terms coming from the analog threshold variations of each metal-oxide-semiconductor field-effect transistor (MOSFET). Measurements showed that the operations of the pitaya DSSC sensor and the proposed sensor transducer were correctly verified. With the proposed technique, the highest sensitivity of -2.7326 MHz/V was guaranteed. The sunlight intensity ranged from 67.775 to 190.45 W/m
²
, with the corresponding frequency ranging from 2.83 to 4.49 MHz. A maximum linear error of 0.79% was obtained. Sensitivity of -10.997 (kHz/W/m
²
) was measured, and the chip area was 1.49 × 1.49 mm
²
. Eventually, an experiment was conducted for monitoring orchid environmental sunlight intensity. The results proved that the proposed chip was suitable for measuring sunlight intensity inside greenhouses.