# A near-infrared Sn-Pb perovskite imager with monolithic integration

## TL;DR

A new Sn-Pb perovskite imager with improved performance is developed for near-infrared sensing and imaging.

## Contribution

A Sn(SCN)2 surface passivation strategy is introduced to enhance Sn-Pb perovskite photodetectors for monolithic integration.

## Key findings

- The imager achieves a dark current density of 10 nA cm−2 and a detectivity of ~1.6 × 1013 Jones.
- It features a 640 × 512 pixel array with 76% external quantum efficiency at 940 nm.
- The device demonstrates material recognition capabilities for chemical sensing and biomedical imaging.

## Abstract

Solution-processed Sn-Pb perovskites have emerged as promising candidates for near-infrared (NIR) photodetectors due to their low-cost, tunable bandgap and scalable fabrication. However, Sn2+ oxidation creates Sn vacancies and undesirable p-type doping, resulting in high dark current and limited detectivity, which hinder the practical deployment of Sn-Pb perovskite photodetectors. Herein, we propose a Sn(SCN)2 inorganic molecular surface passivation strategy to suppress Sn2+ oxidation, significantly reduce surface defect density and enhance the optoelectronic properties (a dark current density of 10 nA cm−2 at a bias of −0.1 V and a high specific detectivity of ~1.6 × 1013 Jones). Leveraging this approach, we report the monolithically integrated Sn-Pb perovskite NIR imager with a complementary metal-oxide-semiconductor readout circuit. The imager, featuring a 640 × 512 pixel array with a 15 μm pixel pitch, achieves an external quantum efficiency of 76% at 940 nm and a modulation transfer function of 206.5 LW/PH at 50%. Furthermore, the Sn-Pb perovskite imager demonstrates advanced material recognition capabilities, including liquid identification, underscoring its potential in chemical sensing, biomedical imaging and industrial inspection.

Monolithic Sn-Pb perovskite NIR imager with Sn(SCN)2 passivation achieves low dark current, high detectivity and material recognition for advanced sensing and imaging.