High-performance, mini modules (∼1 cm²) of halide perovskite indoor photovoltaics with carbon counter electrode and sensor powering

Halide perovskite indoor photovoltaics present a promising pathway for sustainably powering the rapidly growing network of wireless sensors in the Internet of Things. However, the widespread adoption of these devices is hindered by the use of costly and unstable metal back electrodes such as gold (Au) and silver (Ag). In this study, we demonstrate a scalable, single-step blade-coating method for depositing carbon back electrodes and investigate their performance in conjunction with various hole-selective layers (HSLs). Among the various HSLs tested, Spiro-OMeTAD and CuSCN, when paired with the carbon electrode, showed the best performance, achieving power conversion efficiencies (PCEs) of up to 17.2% under 1000 lux indoor illumination for 1 cm² devices. In comparison, their Au-based counterparts reached a higher PCE of 29.3%. Shelf-life stability studies on unencapsulated devices revealed that the extent of J–V hysteresis and PCE degradation strongly depends on the choice of HSL/electrode combination. However, for all devices, regardless of the selected HSL, a gradual increase in hysteresis was observed over time. Finally, mini-modules of carbon-based halide perovskite indoor PV devices were successfully used to power a temperature sensor for indoor temperature monitoring.