Ambient processed highly stable self-powered lead-free Cs2AgBiBr6 double perovskite photodetector in HTM-free architecture with Carbon as electrode

Abstract

Conventional Lead-based hybrid perovskite photodetectors face significant challenges due to toxicity and poor ambient stability. This study contributes to the development of sustainable and efficient photodetectors by leveraging the exceptional properties of Lead-free Cs₂AgBiBr₆ double perovskite. A key feature of this work is the use of Cs₂AgBiBr₆ in a hole transport material (HTM)-free architecture with carbon electrodes, simplifying fabrication and enhancing device stability. The Cs₂AgBiBr₆ films are fabricated using a one-step spin-coating method under ambient conditions. Structural and optical analysis confirms the formation of a cubic perovskite phase with a 2.02 eV bandgap. The photodetector operates in a self-powered mode, detecting a broad spectral range from 350 to 600 nm, with impressive responsivity (50 mA/W), detectivity (5.1 × 10¹¹ Jones), and a fast rise time (160 ms). The Type-II band alignment at the Cs₂AgBiBr₆-TiO₂ interface enables the self-powered operation. The inherent structural stability of Cs₂AgBiBr₆ results in excellent durability, maintaining performance over multiple photocycles (>500), prolonged exposure to simulated sunlight (>1 h), high humidity (RH ∼ 90 % for 4 h), and elevated temperatures (80 °C for 4 h). Moreover, the device retained its responsivity for more than 60 days when stored under ambient conditions without encapsulation. With its simplified HTM-free architecture and Carbon electrode, the detector exhibits excellent photoresponse and resilience under harsh conditions, demonstrating the potential of Cs₂AgBiBr₆ in addressing the lead toxicity and stability issues in photodetectors.