Abstract
By harvesting low-intensity ambient light, indoor photovoltaics (PVs) could soon power countless internet-of-things (IoT) devices and sensors. However, indoor illumination conditions vary from room to room and even hour to hour, leading to inconsistent PV power generation. To overcome this, energy-harvesting circuitry can be used alongside indoor PV modules to recharge batteries or capacitors, forming energy-harvesting systems that enable consistent discharge into IoT devices. The optimisation of such systems is a topic of intense research. In this work, we use thermodynamic principles to model power generation in indoor PV modules based on inorganic, perovskite, and organic semiconductors, before evaluating the efficiency of the whole energy-harvesting system. In these investigations, we account for detailed device physics, including sub-gap absorption, band-filling effects, point defects, and parasitic resistances, while also considering performance under several different light sources. Ultimately, we find that the maximum power point voltage ( V mpp ) is pivotal in determining the optimal number of cells for an indoor PV module. Despite some PV materials having a lower V mpp due to narrower bandgaps or increased voltage losses, we find that this can be compensated for by increasing the number of cells; though too many cells can actually lead to inefficient energy harvesting. As a final case study, we evaluate the power generated and stored in a typical day (where an interplay between daylight and artificial light is present) to determine how stored energy translates to measurements made with an IoT device.
| Original language | English |
|---|---|
| Article number | 035019 |
| Journal | Journal of Physics: Energy |
| Volume | 7 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - 31 Jul 2025 |
| MoE publication type | A1 Journal article-refereed |
Funding
We kindly acknowledge Cati Steed and Professor Trystan Watson (SPECIFIC, Swansea University) for fruitful discussions on the singulation of solution-processed PV modules. This work was funded by the UKRI through the EPSRC Program Grant EP/T028513/1 ‘Application Targeted and Integrated Photovoltaics’. This work was also supported through the Welsh Government’s Sêr Cymru II Program ‘Sustainable Advanced Materials’ (European Regional Development Fund, Welsh European Funding Office and Swansea University Strategic Initiative). O J S acknowledges funding from the Research Council of Finland through Project No. 357196. P M is a Sêr Cymru II Research Chair and A A was a Rising Star Fellow. G B was supported through the EPSRC Program Grant EP/Y024060/1 ‘Switch to Net Zero Buildings: Place-Based Impact Acceleration Account’.