The global transition toward renewable energy requires technologies that combine high efficiency, low cost, and environmental sustainability. Among emerging photovoltaic (PV) options, perovskite solar cells (PSCs) stand out due to their excellent optoelectronic properties, solution-processability, and rapid increase in power conversion efficiencies (PCEs), now surpassing 25%. However, large-scale commercialization remains hindered by two major challenges: the environmental risks associated with lead content and the high cost of critical raw materials, particularly indium, tin, silver, and gold. These elements, widely used in transparent conductive oxides (TCOs) and metallic electrodes, represent a significant fraction of device cost and face increasing supply risks. Recycling and reusing these components is therefore essential to enable sustainable deployment of PSC technology.

In this work, we present two environmentally benign chemical routes for recovering indium tin oxide (ITO)-coated glass substrates from decommissioned PSCs. Devices were immersed in diluted citric acid or potassium hydroxide (KOH) solutions to dissolve the functional layers. The resulting substrates were analyzed and compared with pristine ITO in terms of structural, optical, and electrical properties.

Comprehensive characterization revealed that KOH treatment is the most effective recycling route. X-ray diffraction (XRD) confirmed that the ITO crystalline structure was preserved, while atomic force microscopy (AFM) showed a uniform surface morphology comparable to reference samples. UV–vis spectroscopy demonstrated that the optical transmittance of KOH-recycled substrates closely matched that of pristine ITO, whereas citric acid induced partial lixiviation, reducing thickness and transparency. Four-point probe measurements confirmed that KOH-treated substrates retained low sheet resistance and high conductivity, while citric acid significantly degraded the electrical performance.  The figure of merit (FOM), combining transmittance and sheet resistance, further validated the superior performance of KOH-recycled ITO, which exhibited values nearly identical to pristine references. To demonstrate practical feasibility, new PSCs employing wide bandgap absorbers were fabricated on the recovered substrates. Remarkably, these devices delivered average PCEs of 18%, indistinguishable from those obtained with virgin ITO. Key photovoltaic parameters—including short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF)—remained stable, and no hysteresis was detected.

These findings highlight that KOH-based recycling enables efficient recovery of ITO-coated glass substrates under mild, room-temperature conditions without the need for aggressive solvents. By contrast, citric acid, while also benign, promotes corrosion that compromises substrate integrity.

In summary we demonstrate a robust and scalable strategy to recycle and reuse ITO substrates from PSCs, preserving their functional properties and enabling their integration into new high-performance devices. This approach reduces production costs, mitigates electronic waste, and addresses the scarcity of indium, a critical raw material. The proposed method thus represents a practical and sustainable pathway toward circularity in perovskite solar cell technology, supporting the broader deployment of renewable energy solutions with reduced environmental impact.