Infrared Cavity-Enhanced Colloidal Quantum Dot Photovoltaics Employing Asymmetric Multilayer Electrodes

Efficient infrared (IR) optoelectronic devices, crucial for emerging sensing applications and also for solar energy harvesting, demand high-conductivity IR-transparent electrodes. Here we present a new strategy, one based on oxide/metal/oxide multilayers, that enables highly transparent IR electrodes. Symmetry breaking in the oxide stack leads to broad and high transmittance from visible to IR wavelengths, while a low refractive index doped oxide as a front layer boosts IR transmittance. The combination of doped oxide and ultrathin metal film allows for low sheet resistance while maintaining IR transparency. We engineer the IR microcavity effect using the asymmetric multilayer approach to tailor the distribution of incident radiation to maximize IR absorption in the colloidal quantum dot (CQD) layer. As a result, the absorption-enhanced IR CQD solar cells exhibit a photoelectric conversion efficiency of 70% at a wavelength of 1.25 μm, i.e., well within the spectral range in which silicon is blind.