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Title: Ab Initio Simulation of Charge Transfer at the Semiconductor Quantum Dot/TiO 2 Interface in Quantum Dot-Sensitized Solar Cells

Quantum dot-sensitized solar cells (QDSSCs) have emerged as a promising solar architecture for next-generation solar cells. The QDSSCs exhibit a remarkably fast electron transfer from the quantum dot (QD) donor to the TiO2 acceptor with size quantization properties of QDs that allows for the modulation of band energies to control photoresponse and photoconversion efficiency of solar cells. In order to understand the mechanisms that underpin this rapid charge transfer, the electronic properties of CdSe and PbSe QDs with different sizes on the TiO2 substrate are simulated using a rigorous ab initio density functional method. Our method capitalizes on localized orbital basis set, which is computationally less intensive. Quite intriguingly, a remarkable set of electron bridging states between QDs and TiO2 occurring via the strong bonding between the conduction bands of QDs and TiO2 is revealed. Such bridging states account for the fast adiabatic charge transfer from the QD donor to the TiO2 acceptor, and may be a general feature for strongly coupled donor/acceptor systems. All the QDs/TiO2 systems exhibit type II band alignments, with conduction band offsets that increase with the decrease in QD size. This facilitates the charge transfer from QDs donors to TiO2 acceptors and explains the dependencemore » of the increased charge transfer rate with the decreased QD size.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [1]
  1. Georgia Inst. of Technology, Atlanta, GA (United States)
  2. Iowa State Univ., Ames, IA (United States)
Publication Date:
OSTI Identifier:
1226915
Report Number(s):
IS--J 8567
Journal ID: ISSN 0934-0866
Grant/Contract Number:
AC02-07CH11358
Type:
Accepted Manuscript
Journal Name:
Particle & Particle Systems Characterization
Additional Journal Information:
Journal Volume: 32; Journal Issue: 1; Journal ID: ISSN 0934-0866
Publisher:
Wiley
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 25 ENERGY STORAGE quantum dot-sensitized solar cells; CdSe and PbSe quantum dots; ab initio simulation; charge transfer; bridging state