CdSe Solar Cell With High Voltage

CdSe is an important material for making a tandem cell with Silicon as the lower gap cell. It has almost a perfect bandgap match (1.72 eV) with Si for a 2-terminal tandem cell. One major problem has ben a low open circuit voltage, being limited to ~0.8V. In this paper, we show that by changing annealing parameters during deposition of the material, we can obtain a voltage of 0.88 V in a hybrid device where the p layer is P3HT. We show that for best passivation of grain boundaries, one needs a mixture of oxygen and nitrogen during the annealing treatment. We also measure subgap quantum efficiency and show that the material has a low Urbach energy for valence band tail states, implying the potential for high voltages (>1 V) in this material.