Study of interface engineering on perovskite-based indoor photovoltaics for powering Internet-of-Things

•Halide perovskites have an ideal bandgap for low-intensity indoor light, making them promising for indoor photovoltaics (IPVs).•Trap-assisted recombination is an important charge recombination mechanism in perovskite-based IPVs (PeIPVs) under low-intensity conditions.•Interface engineering is key to the performance of PeIPVs, since recombination-causing defects are primarily located at interfaces.•We have categorized interface studies in PeIPVs into surface, transport layer, and precursor engineering, focusing on their main effects.•This review also included the discussion of flexible PeIPVs, modularization, and IoT applications through interface engineering, and suggested future research directions. Research on perovskite-based indoor photovoltaics (PeIPVs) has attracted significant interest in Internet of Things (IoT) sensors owing to their potential use as power sources. This interest stems from the fact that PeIPVs offer advantages such as a suitable bandgap for indoor light sources, light-emitting diode (LED), and excellent defect tolerance. However, because the intensity of indoor LED light sources is 333 times weaker than that of 1 sun (AM1.5G, 100 mW cm−2), charge recombination in PeIPVs changes compared with that in conventional solar cells, shifting from bimolecular recombination to trap-assisted recombination. Given these differences, the research methodology for PeIPVs requires a focus on controlling the interfacial defects, diverging from conventional solar cell research approaches. In general, the interfaces between the perovskite and other layers in perovskite-based photovoltaic devices have a relatively high trap density compared to the interior of the perovskite, owing to incomplete reactions or non-ideal heterojunctions. The interfacial defect-sensitive property of IPV has prompted researchers to address these challenges through various interface engineering techniques such as surface treatment, electron transport layer (ETL)/hole transport layer (HTL) engineering, and precursor engineering, significantly improving efficiency. In this review, we discuss the research outlook by analyzing the trends and critical factors in PeIPVs and research based on interface engineering around perovskite interfaces. Furthermore, the potential applications of PeIPV research are outlined through examples such as flexible configurations and modularization for powering real-world Internet of Things sensors.