[16p-304-1~13] Photovoltaic 4.0 －高効率・低コスト太陽光発電がもたらす次世代再生可能エネルギーシステム－

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

〇岡田 至崇^1,2、庄司 靖¹、吉田 勝尚¹、内藤 駿弥²、玉置 亮^1,2 (1.東大先端研、2.東大院工)

キーワード：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.