Publication date: 15th December 2025
Abstract:
The increasing demand for cost-effective, high-sensitivity short-wavelength infrared (SWIR) photodetectors has driven significant research into solution-processable materials. Colloidal quantum dots (CQDs), particularly III-V semiconductors like InAs, offer a promising and RoHS-compliant alternative to traditional epitaxially grown InGaAs sensors, especially for applications in medical imaging, autonomous systems, and industrial inspection. While InAs CQDs present an attractive route to SWIR detection due to their size-tunable bandgap and non-toxic composition, the development of efficient photodiode architectures with optimized charge extraction layers remains crucial. In this work, we demonstrate a SWIR photodiode fabricated using InAs CQDs as the active absorbing layer, integrated with a carefully selected stack of solution-processed charge transport layers. The device architecture consists of ITO-coated glass as the transparent bottom contact, a hole-selective polymer layer to facilitate efficient hole extraction and block electrons, the InAs CQD active layer, a zinc oxide (ZnO) nanoparticle layer as the electron transport layer (ETL), and a top silver (Ag) metal contact. The energy level alignment between the polymer hole transport layer, the InAs CQDs, and the ZnO ETL creates a favorable cascade that drives efficient charge carrier separation and minimizes recombination losses. The device characterization reveals high photocurrent for visible (450 and 638 nm) and near infrared wavelengths (980 nm), see figure, confirming the effective function of the photodiode architecture. This study underscores the viability of combining InAs CQDs with tailored organic and metal-oxide charge transport layers to create high-performance, environmentally friendly SWIR photodetectors via low-cost, scalable fabrication methods.
Thanks to the Advanced Materials programme that was supported by MCIN with funding from NextGenerationEU and Generalitat Valenciana (project no. MFA-2022-066), and to the MCIN Project PID2023-151632OB-C21.
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