Perovskite-inspired Cu2AgBiI6 for mesoscopic indoor photovoltaics under realistic low-light intensity conditions

Abstract

The considerable potential of perovskite-inspired Cu₂AgBiI₆ (CABI) photovoltaics under both solar and artificial lighting has been recently highlighted. However, to realistically ensure the suitability of CABI-based indoor photovoltaics (IPVs) to power the Internet of Things (IoT) ecosystem, it is necessary to study how the device performance is affected by very low-light intensity conditions (200–50 lux illumination). In this work, we find that the fine-tuning of the mesoporous TiO₂ (mp-TiO₂) layer thickness is crucial to maximize the performance of mesoporous CABI-based IPVs at both high and very-low artificial light intensity as it directly affects the charge extraction and non-radiative charge recombination in the devices. An optimal mp-TiO₂ thickness of ∼200 nm leads to an indoor power conversion efficiency (PCE(i)) of 5.52% and a fill factor of 69%, which are the highest values for perovskite-inspired based IPVs under 1000 lux white light-emitting diode lighting. Importantly, the devices keep a high fill factor also at very low-light intensity. This guarantees a noteworthy PCE(i) value of 4.64% at 200 lux and an open-circuit voltage (V_OC) of 0.38 V even at 50 lux. Our work suggests that, upon further improvements in the short-circuit current and V_OC values, low-toxicity mesoscopic CABI-based IPVs may approach their theoretical PCE(i) values of 50–60% even under very low-light intensity conditions.