The past three decades have witnessed extensive research in developing a range of non-metallic fused heterocyclic organic dyes for dye sensitized solar cells (DSSCs).

Deploying earth abundant copper as a redox mediator in dye-sensitized solar cells (DSCs) has been found to be a very promising strategy to achieve higher photovoltage and power conversion efficiencies in full sun (100 mW cm ⁻² ) and in low/diffuse light conditions.

Dye-sensitized solar cells (DSCs) have proven to be one of the best photovoltaic approaches for harnessing indoor/artificial light. Herein, we report two new molecularly engineered, cost-effective, metal-free, carbazole-based D–π–A sensitizers (YK 8 and YK 9) by judiciously varying their π-spacers, which are suitable for indoor photovoltaic applications. Using YK 8, we achieved an efficiency of 28.7% under standard 1000 lux Osram 14 W T2 cool day light fluorescent tube illumination with a power output of 68.88 μW cm⁻² and 30.24% with a power output of 108.85 μW cm⁻² under a higher illumination intensity of 1500 lux without co-sensitizers using iodide/triiodide electrolyte. With a small footprint/active area of 1.24 cm², we could power a temperature sensor completely autonomously at a low light intensity of 500 lux, displaying the potential of these indoor photovoltaic devices to serve as energy sources for low-power sensors and actuators on the Internet of Things (IoT) network, reducing the dependence on batteries and leading to a smaller carbon footprint. The role of the π-spacer and its influence on recombination and device performance were explored via extensive interfacial studies.

Addressing undesirable recombination in indoor light harvesting dye-sensitized solar cells using innovative dual species copper electrolyte concept realizing a record PCE of 35.6%. A sustainable alternative to primary batteries for self-powered IoTs & indoor photovoltaics.