A Donor-Supply Electrode (DSE) for Colloidal Quantum Dot Photovoltaics
2011; American Chemical Society; Volume: 11; Issue: 12 Linguagem: Inglês
10.1021/nl202337a
ISSN1530-6992
AutoresGhada I. Koleilat, Xihua Wang, André J. Labelle, Alexander H. Ip, Graham H. Carey, A. Fischer, Larissa Levina, Lukasz Brzozowski, Edward H. Sargent,
Tópico(s)Advanced Photocatalysis Techniques
ResumoThe highest-performing colloidal quantum dot (CQD) photovoltaics (PV) reported to date have relied on high-temperature (>500°C) annealing of electron-accepting TiO2. Room-temperature processing reduces energy payback time and manufacturing cost, enables flexible substrates, and permits tandem solar cells that integrate a small-bandgap back cell atop a low-thermal-budget larger-bandgap front cell. Here we report an electrode strategy that enables a depleted-heterojunction CQD PV device to be fabricated entirely at room temperature. We find that simply replacing the high-temperature-processed TiO2 with a sputtered version of the same material leads to poor performance due to the low mobility of the sputtered oxide. We develop instead a two-layer donor-supply electrode (DSE) in which a highly doped, shallow work function layer supplies a high density of free electrons to an ultrathin TiO2 layer via charge-transfer doping. Using the DSE we build all-room-temperature-processed small-bandgap (1 eV) colloidal quantum dot solar cells having 4% solar power conversion efficiency and high fill factor. These 1 eV bandgap cells are suitable for use as the back junction in tandem solar cells. The DSE concept, combined with control over TiO2 stoichiometry in sputtering, provides a much-needed tunable electrode to pair with quantum-size-effect CQD films.
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