[16p-304-1~13] Photovoltaic 4.0 - Next-generation renewable energy systems powered by high-efficiency, low-cost photovoltaics -

▲ [16p-304-8] Recent Progress of Quantum Dot Intermediate Band Solar Cells

〇Yoshitaka Okada^1,2, Yasushi Shoji¹, Katsuhisa Yoshida¹, Syunya Naito², Ryo Tamaki^1,2 (1.RCAST, Univ. Tokyo, 2.Dept. EEIS, Univ. Tokyo)

Keywords:quantum dot solar cells, intermediate band solar cells, two-step photon absorption

On-going progress and challenges on the development of quantum dot based intermediate band solar cells (QD-IBSC) are reviewed. For QD-IBSCs reported till today, the cells suffer from small absorption and low QD densities, lead to a drop of the open-circuit voltage and hence efficiency. The areal density of QDs inevitably has a direct influence on the generation and recombination processes via IB. For a common InAs/GaAs QD system, it is calculated that the net gain of photocurrent production can be achieved with 100 suns and higher for the QDs areal density of 1×10¹² cm^-2. The carrier lifetime and occupancy rate in IB are other important parameters that directly affect the conversion efficiency of QD-IBSCs. These parameters are determined by the carrier recombination strength, and thermal and tunneling escape rates out of QDs. A long electron lifetime is obtained by controlling the recombination rate using a type-II QD heterostructure or ratchet structure.