Integration of Solar Cells on Top of CMOS Chips Part I: a-Si Solar Cells

Development of an Indoor Photovoltaic Energy Harvesting Module for Autonomous Sensors in Building Air Quality Applications

“…The simplified IPEHPM power model shown in formula (9) links all application parameters such as illumination condition (ie_c), measurement period (T), current pulse amplitude (i0) and duration (t0), and the sleep mode current (isleep). Therefore the powering capability of the IPEHPM for a specific IoT node can be directly evaluated using formula (9).…”

“…The simplified IPEHPM power model shown in formula (9) links all application parameters such as illumination condition (ie_c), measurement period (T), current pulse amplitude (i0) and duration (t0), and the sleep mode current (isleep). Therefore the powering capability of the IPEHPM for a specific IoT node can be directly evaluated using formula (9). Since the total discharge is a known value for a specific application, the lowest illumination condition for an IoT application can be determined by calculating ie-c using formula (10) and then using ie-c to determine a suitable illumination condition.…”

“…Therefore formula (10) can be easily explained as the effective charge current of the IPEHPM should not be less than the average load current of the IoT node. Similarly, for a specific illumination condition, the minimum available measurement period can be calculated via formula (9) as well,…”

“…The long lifetime of energy harvesting and storage components (such as millions of recharge circles for a supercapacitor) enables the IoT-based sensor node to be powered using energy harvesting in a "fit and forget" manner without worrying about battery replacement. Attempts at integrating PV cells, power management circuits and even storage together to provide a fully integrated PV energy harvesting power chip which finally leads to selfpowered IoT systems have been reported [9][10][11]. However due to the chip size restriction, the total harvested energy is limited so it is suitable for some ultra-low power applications but is not generic for powering a low-power IoT-based sensor node.…”

State of the art in Microfabrication

“…Various groups investigate photovoltaic systems-on-foil, a technology that could offer extremely low-radiation length semiconductor junctions, an attractive feature for particle tracking. Alternatively, the photovoltaic technology may be transferable directly to a CMOS pixel readout chip, as has been shown for a-Si and CIGS [33][34][35][36].…”