Efficient semi-transparent perovskite quantum dot photovoltaics enabled by asymmetric dielectric/metal/dielectric transparent electrodes

CsPbI₃ perovskite quantum dots (CsPbI₃-PQDs) have a high potential as semi-transparent photovoltaic absorbers because of the facile control of film thicknesses, size-tunable optical band gaps, and nanometer-scale grain sizes suppressing light scattering. Conventional semi-transparent CsPbI₃-PQD solar cells showed low photovoltaic performances due to the low electrical conductivity of the graphene electrodes. Here we report that dielectric/ultra-thin metal/dielectric (DMD) electrodes with excellent optical transmittance and electrical conductivity deliver superior photovoltaic performances in the semi-transparent CsPbI₃-PQD solar cells. Particularly, the asymmetric DMD electrodes composed of MoO_x 15 nm/Au 10 nm/MoO_x 35 nm (asym-MAM) stacks exhibit higher optical transmittance than that of the symmetric MoO_x 15 nm/Au 10 nm/MoO_x 15 nm (sym-MAM) stacks. The optical simulation confirms that asym-MAM stacks reduce the parasitic absorption loss in metal interlayers. Therefore, the asym-MAM stacks with a high electrical conductivity show a higher average visible transmittance (AVT) than that of the sym-MAM. Consequently, the semi-transparent CsPbI₃-PQD solar cells fabricated using the asym-MAM transparent top electrodes show a power conversion efficiency of 11.3% with a considerable AVT values of 23.4% (400–800 nm) and 20.0% (380–780 nm), respectively, which were calculated from their transmittance spectra. This is the highest-efficiency semi-transparent PQD solar cells that can be used for solar window applications requiring an AVT value of over 20%.