Heavy-metal-free solution-processed nanoparticle-based photodetectors: doping of intrinsic vacancies enables engineering of sensitivity and speed.

Photodetection in semiconductors enables digital imaging, spectroscopy, and optical communications. Integration of solution-processed light-sensing materials with a range of substrates offers access to new spectral regimes, the prospect of enhanced sensitivity, and compatibility with flexible electronics. Photoconductive photodetectors based on solution-cast nanocrystals have shown tremendous progress in recent years; however, high-performance reports to date have employed Pb- and Cd-containing materials. Here we report a high-sensitivity (photon-to-electron gain >40), high-speed (video-frame-rate-compatible) photoconductive photodetector based on In(2)S(3). Only by decreasing the energetic depth of hole traps associated with intrinsic vacancies in beta-phase In(2)S(3) were we able to achieve this needed combination of sensitivity and speed. Our incorporation of Cu(+) cations into beta-In(2)S(3)'s spinel vacancies that led to acceptable temporal response in the devices showcases the practicality of incorporating dopants into nanoparticles. The devices are stable in air and under heating to 215 degrees C, advantages rooted in the reliance on the stable inclusion of dopants into available sites instead of surface oxide species.