Programmable semiconductor switches its electronic properties under UV light

A research team from PDI and Leibniz Universität Hannover has developed a new class of programmable semiconducting material by integrating light-responsive molecular switches directly into the bulk of a crystalline semiconductor. The study, published in Advanced Functional Materials, opens pathways toward all-optical computing, adaptive electronics, and energy-efficient information processing.

The research focuses on a layered hybrid perovskite material in which organic coumarin-based photoswitch molecules are interleaved between inorganic lead-bromide semiconductor layers. Unlike traditional semiconductors such as silicon or common III–V and II–VI compounds, whose electronic and optical properties are fixed after fabrication, this hybrid system can reversibly change its optical and electronic behaviour in response to light.

At the heart of this functionality is a photo-induced chemical reaction known as a [2 + 2] cycloaddition: when illuminated with UV-A light (~365 nm), the organic spacers dimerize, transforming their molecular structure. This change induces local distortions in the inorganic lattice, modifying the band structure of the semiconductor and shifting its bandgap and photoluminescence characteristics. The reaction can be driven to about 70 % conversion and can be partially reversed with higher-energy UV-C light (~254 nm), demonstrating tunable and reversible optoelectronic switching.

Importantly, the photoswitching occurs throughout the volume of the crystals, meaning that the entire semiconductor bulk becomes programmable via light. The degree of switching directly correlates with shifts in optical absorption and emission, and the structural changes can be mapped with high spatial precision using fluorescence and Raman microscopy.

This programmable light-responsive behaviour is especially relevant for emerging technologies that merge computation and memory, such as optical neuromorphic processors, in-memory computing, and adaptive photonic devices, where materials must dynamically encode information and react to optical signals without electrical interfacing.

The study was carried out by PDI's Hans Tornatzky and Markus R. Wagner, along with collaborators Oliver Treske, Yaşar Krysiak, and Sebastian Polarz, from the Leibniz Universität Hannover.

By embedding functional molecular switches within a semiconductor’s crystal lattice, this work marks a significant advance toward adaptive and programmable materials that could transform how information is stored, processed, and controlled in next-generation electronic and photonic systems.

Title: A programmable semiconductor containing active molecular photoswitches located in the crystal's volume phase
Authors: O. Treske, Y. Krysiak, H. Tornatzky, M. R. Wagner, S. Polarz
Source: Adv. Funct. Mater., tba, e24426 (2025)
DOI: 10.1002/adfm.202524426