Photoconductive Materials in Solar and X-Ray Detection Systems

Photoconductive materials underpin the conversion of electromagnetic radiation into electrical signals across solar and X-ray detection platforms. In photovoltaics, these materials absorb photons to generate charge carriers, while in direct-conversion X-ray detectors they transduce high-energy photons directly into electron–hole pairs. Seminal developments have focused on chalcogenides such as selenium and lead oxide, together with cadmium telluride, to strike an optimal balance between absorption efficiency, carrier transport and fabrication simplicity. Advances in crystallinity, interface engineering and device architecture have progressively improved sensitivity, spatial resolution and temporal response. Global efforts now address scalability, environmental sustainability and multi-junction integration, driving photoconductive materials into applications from indoor energy harvesting to medical and scientific imaging.

Research from Nature Portfolio

Recent studies have advanced the performance of photoconductive layers in imaging systems. Hybrid structures integrating crystalline selenium photoconversion layers with high-resolution CMOS field-effect transistors have demonstrated avalanche multiplication of photogenerated carriers, achieving signal gain around 1.4 without elevating noise at practical bias voltages. This approach counters sensitivity loss in pixel-miniaturised sensors and suggests pathways to ultra-high-definition imaging. Separately, a bilayer device combining amorphous and polycrystalline lead oxide exploits the high X-ray stopping power of poly-PbO for charge generation while an overlying a-PbO layer suppresses signal lag. The bilayer architecture delivers real-time imaging capability with carrier transport analogous to commercial amorphous selenium detectors yet extends performance into higher-energy X-ray regimes.

Photoconductive Materials in Solar and X-Ray Detection Systems publication trend

The graph below shows the total number of articles in photoconductive materials in solar and x-ray detection systems across all publications each year (not limited to Nature Index journals).

Technical terms

Photoconductivity: Increase in electrical conductivity of a material upon absorption of photons due to generation of electron–hole pairs.

Avalanche multiplication: Process in which photogenerated carriers acquire sufficient energy under high electric field to create additional electron–hole pairs via impact ionisation, resulting in signal amplification.

Schottky diode: Metal–semiconductor junction device that rectifies current and is employed as a direct-conversion detector architecture for X-ray sensing.

Carrier mobility–lifetime product (µτ): Material parameter representing the product of carrier mobility and recombination lifetime, governing charge collection efficiency.

Direct-conversion detector: Imaging device that directly converts incident X-ray photons into electrical charge without intermediate scintillation.

Open-circuit voltage (Voc): Maximum voltage available from a photovoltaic device under illumination when no external load is connected.

Fill factor: Ratio of the actual maximum obtainable power to the product of Voc and short-circuit current, quantifying solar cell performance.

References

1. Enhanced image sensing with avalanche multiplication in hybrid structure of crystalline selenium photoconversion layer and CMOSFETs. Scientific Reports (2020).
2. Bilayer lead oxide X-ray photoconductor for lag-free operation. Scientific Reports (2020).
3. Sustainable Recycling of Selenium‐Based Optoelectronic Devices. Advanced Science (2024).
4. Monolithic Selenium/Silicon Tandem Solar Cells. PRX Energy (2024).
5. Tuning Amorphous Selenium Composition with Tellurium to Improve Quantum Efficiency at Long Wavelengths and High Applied Fields. ACS Applied Electronic Materials (2023).