Multijunction solar cells offer a route to exceed the Shockley-Queisser limit for single-junction devices. In a few short years, silicon-perovskite tandems have significantly passed the efficiency of the best silicon single-junction cells. For scalable solution processing of silicon-perovskite tandem devices, with the avoidance of vacuum processing steps, a flat silicon sub-cell is normally required. This results in a flat top surface that can lead to higher optical reflection losses than conformal deposition on textured silicon bottom cells. To overcome this, textured anti-reflective coatings (ARCs) can be used on top of the finished cell, with textured polydimethylsiloxane (PDMS), a promising candidate. In this work, we vary the texture geometry and film thickness of PDMS anti-reflective foils to understand the effect of these parameters on reflectance of the foil. The best film is selected, and anti-reflective performance is compared with two common planar ARCs-lithium fluoride (LiF) and magnesium fluoride (MgF₂) showing considerable reduction in reflectance for a non-textured silicon-perovskite tandem cell. The application of a PDMS film is shown to give a 3-5% increase in integrated J _SC in each sub-cell of a silicon-perovskite tandem structure.

The complete interpretation of small perturbation frequency‐domain measurements on perovskite solar cells has proven to be challenging. This is particularly true in the case of intensity‐modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) measurements in which the high frequency response is obscured by instrument limitations. Herein, a new experimental methodology capable of accurately resolving the high frequency response—often observable in the second and third quadrants of the complex plane—of a range of perovskite devices is demonstrated. By combining single‐frequency IMPS/IMVS measurements, it is able to construct the time dependence of the IMPS/IMVS response of these devices during their initial response to illumination. This reveals significant negative photocurrent/photovoltage signals at high frequency while devices reach steady state, which is in keeping with observations made from comparable time‐domain transient measurements. These techniques allow the underlying interfacial recombination and ion migration processes to be assessed, which are not always evident using steady‐state measurements. The ability to study and mitigate these processes is vital in optimizing the real‐world operation of devices.

As the Internet of Things (IoT) expands, the need for energy-efficient, self-powered devices increases and so a better understanding of the available energy resource is necessary. We examine the light power resource availability for energy harvesting photovoltaics (PV) in various environments and its potential for self-powered IoT applications. We analyse light sources, considering spectral distribution, intensity, and temporal variations, and evaluate the impact of location, seasonal variation, and time of day on light power availability. Additionally, we discuss human and building design factors, such as occupancy, room aspect, sensor placement, and décor, which influence light energy availability and therefore power for IoT electronics. We propose a best-case and non-ideal scenario in terms of light resource for energy-harvesting, and using a commercially available organic PV cell, show that the energy yield generated and available to the IoT electronics, can be anywhere between 0.7 mWh and 75 mWh per day, depending on the lighting conditions.

The number of interconnected devices, often referred to as the Internet of Things (IoT), is increasing at a considerable rate. It is inevitable therefore that so too will the energy demand. IoT describes a range of technologies such as sensors, software, smart meters, wearable devices, and communication beacons for the purpose of connecting and exchanging data with other devices and systems over the internet. Often not located near a mains supply power source, these devices may be reliant on primary battery cells. To avoid the need to periodically replace these batteries, it makes sense to integrate the technologies with a photovoltaic (PV) cell to harvest ambient light, so that the technologies can be said to be self-powered. Perovskite solar cells have proven extremely efficient in low-light conditions but in the absence of ambient and low-light testing standards, or even a consensus on what is defined by “ambient light”, it is difficult to estimate the energy yield of a given PV technology in a given scenario. Ambient light harvesting is complex, subject to spectral considerations, and whether the light source is directly incident on the PV cell. Here, we present a realistic scenario-driven method for measuring the energy yield for a given PV technology in various situations in which an IoT device may be found. Furthermore, we show that laboratory-built p-i-n perovskite devices, for many scenarios, produce energy yields close to that of commercial GaAs solar cells. Finally, we demonstrate an IoT device, powered by a mesoporous carbon perovskite solar module and supercapacitor, and operating through several day–night cycles.

Implantable biomedical electronics, such as pacemakers, drug pumps, cochlear implants, cardioverter-defibrillators, and neurological stimulators, help humans to overcome various diseases. Currently, the power supply for these devices relies on small-size batteries, and replacement of the battery is required after running for a period of time. Recharging the battery could be a way to prolong the replacement cycle. Organic photovoltaics (OPVs) are a class of emerging photovoltaics, which are now becoming more practical with recently developed device and material engineering. The absorption of OPVs using a non-fullerene acceptor (NFA) could be extended to the near-infrared (NIR) region to cover the transmission window of human skin between 650 and 1000 nm. Motivated by this, we conducted a study of NFA-based OPVs under light irradiation of wavelengths of 650–1000 nm for implants. The devices using donor (PTB7-Th) and NFA (IEICO-4F) as the active material have strong absorption in the NIR region and obtained a promising power conversion efficiency (PCE) of 14.3% under the implant light illumination, compared to 8.11% when using a benchmark fullerene derivative-based acceptor (PC₇₁BM). Importantly, the PCE and power density of the NFA-based OPVs are significantly higher than the previously reported fullerene-based OPVs devices. This study shows that NFA-based OPVs have high potential for future applications in powering implants, e.g., through charging batteries.