Efficient Quantum Dot Solar Cells with Sustainable Oxide Thin Films

Thin-film solar cells provide promising solutions for low-cost, large-area photovoltaic

applications. While cadmium telluride (CdTe), copper indium gallium selenide (CIGS), and

perovskite materials have dominated research on thin-film solar cells, concerns about material

stability, scarcity of rare elements, and environmental impact motivate the search for more

sustainable alternatives. Zinc oxide (ZnO) and molybdenum trioxide (MoO₃) are attractive

options due to their abundance, environmental stability, and compatibility with scalable thin-film

processes.

Here, we demonstrate highly efficient quantum dot solar cells (QDSCs) using sustainable ZnO

and MoO₃ thin films as electron and hole transport layers, respectively. Our approach

strategically optimizes film quality and thickness to reduce interface defects that often affect

nanostructured counterparts. Using deep UV pulsed laser deposition (PLD) at 266 nm, we

produce high-quality ZnO films with minimal oxygen vacancies and transparent MoO₃ films

under ambient oxygen conditions at room temperature.

The optimized device structure includes ITO/ZnO (80 nm)/CdSe-ZnS quantum dots (various

volumes)/MoO₃ (20 nm)/Au, achieving an impressive power conversion efficiency of 11.4%.

This marks a significant improvement over previous ZnO nanostructure-based QDSCs, which

ranged from 3.45 to 4.68%. Our systematic optimization shows that 80 nm ZnO films provide

ideal semiconducting properties, while 20 nm MoO₃ films ensure effective hole transport with

minimal series resistance.

The presentation covers thin-film synthesis, structural and optical characterization via FESEM,

UV-vis spectroscopy, and photoluminescence measurements, along with a comprehensive

analysis of device performance, including current-voltage characteristics and impedance

studies. We will highlight the critical role of interface quality in maximizing charge separation

and transport efficiency.

This work illustrates the potential of sustainable oxide thin films for high-performance QDSCs

and offers a scalable pathway for earth-abundant solar energy harvesting technologies.