Depleted-Heterojunction Colloidal Quantum Dot Solar Cells

Colloidal quantum dot (CQD) photovoltaics combine low-cost solution processability with quantum size-effect tunability to match absorption with the solar spectrum. Rapid recent advances in CQD photovoltaics have led to impressive 3.6% AM1.5 solar power conversion efficiencies. Two distinct device architectures and operating mechanisms have been advanced. The first-the Schottky device-was optimized and explained in terms of a depletion region driving electron-hole pair separation on the semiconductor side of a junction between an opaque low-work-function metal and a p-type CQD film. The second-the excitonic device-employed a CQD layer atop a transparent conductive oxide (TCO) and was explained in terms of diffusive exciton transport via energy transfer followed by exciton separation at the type-II heterointerface between the CQD film and the TCO. Here we fabricate CQD photovoltaic devices on TCOs and show that our devices rely on the establishment of a depletion region for field-driven charge transport and separation, and that they also exploit the large bandgap of the TCO to improve rectification and block undesired hole extraction. The resultant depletedheterojunction solar cells provide a 5.1% AM1.5 power conversion efficiency. The devices employ infrared-bandgap size-effect-tuned PbS CQDs, enabling broadband harvesting of the solar spectrum. We report the highest opencircuit voltages observed in solid-state CQD solar cells to date, as well as fill factors approaching 60%, through the combination of efficient hole blocking (heterojunction) and very small minority carrier density (depletion) in the large-bandgap moiety. © 2010 American Chemical Society.

Pattantyus-Abraham AG, Kramer IJ, Barkhouse AR, Wang X, Konstantatos G, et al. (2010) Depleted-Heterojunction Colloidal Quantum Dot Solar Cells. ACS Nano 4: 3374–3380. Available:

This research was supported by Award No. KUS-I1-009-21, made by King Abdullah University of Science and Technology (KAUST). The authors also acknowledge the assistance of L. Brzozowski, S. Huang, K. Kemp, G. Koleilat, J. Tang, E. Palmiano, R. Wolowiec, and D. Jamaskosmanovic. M.G. and M.K.N. thank the Korea Foundation for International Cooperation of Science and Technology through the Global Research Laboratory (GRL) Program funded by the Ministry of Education, Science and Technology, Republic of Korea.

American Chemical Society (ACS)

ACS Nano


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