Indoor energy harvesting with perovskite solar cells for IoT a pplications - a full year monitoring study

Indoor photovoltaics (IPV) hold enormous market potential driven by the rising demand for perpetual energy sources to power various small electrical devices and especially Internet of things (IoT) devices. Perovskite solar cells (PSCs) offer exciting prospects for this role. This study sets out to deepen our knowledge of PSC performance under realistic indoor conditions. For this purpose, we designed an indoor monitoring system that maintains four solar cells at their maximum power points and simultaneously logs their performance and environmental conditions. Throughout a 12-month period, we monitored the behavior of three PSCs and one crystalline silicon solar cell (c-Si SC), all with an active area of approximately 1 cm2. Measured daily energy yields in conjunction with a comparative overview of minimum energy requirements of different wireless technologies indicate that a single 1 cm2 PSC should be enough to power an IoT device with one of the available short-range, low-power wireless technologies on most days of the year, a fact confirmed by a prototype device. There are, however, a few days every year when the available energy would not be enough to even power the maximum power point tracking, highlighting the need for at least some energy storage capacity. Solar cell orientation dependence measurements demonstrated a 36% advantage for optimal orientation and a 72% performance drop for the worst orientation compared to horizontal orientation. A one-year energy yield results show a remarkable three-to-one advantage in favor of the best PSC (148.8 mWh/cm2) over the c-Si SC (46.0 mWh/cm2). The best of the three PSCs also retained most of its initial performance throughout the year with a simple edge-sealing encapsulation.