Title :
Optical study of carrier transport in InAs/GaAs quantum dots solar cell
Author :
Yushuai Dai ; Hellstroem, Staffan ; Polly, Stephen ; Hatakeyama, John ; Forbes, David ; Hubbard, Seth
Author_Institution :
NanoPower Res. Lab., Rochester Inst. of Technol., Rochester, NY, USA
Abstract :
Optical transitions and carrier transport in InAs/GaAs self-assembled quantum dots solar cells (QDSC) were investigated via temperature dependent photoluminescence (TDPL) spectroscopy, charge collection efficiency calculated from bias dependent spectral response, and low temperature photo-current measurements. Band structure simulations were used to calculate the tunneling rate and thermal escape rate of electrons in quantum dots under different bias conditions. It is found that, tunneling rate and thermal escape rate of electrons in the quantum dots increase along p-n direction. From TDPL, compared to test structures, ground state electron activation energy decrease 60 meV in QDSC. TDPL also indicates that electrons are the main carriers escaping from the QD confinement if temperature higher than 120K, while holes are the rate limiting carrier if temperature lower than 120K. Charge collection efficiency is greatly improved above the bulk GaAs absorption edge (870nm) under large reverse bias (-4.5V). Low temperature (20K) bias photocurrent shows that ground state carrier can be collected even at 0.7V forward bias. This indicates that hole tunneling may be dominant at low temperature, or electron experiences tunneling then thermal escape.
Keywords :
III-V semiconductors; gallium arsenide; indium compounds; photoconductivity; photoemission; photoluminescence; self-assembly; semiconductor quantum dots; solar cells; spectroscopy; tunnelling; InAs-GaAs; QD confinement; QDSC; TDPL; band structure simulations; bias dependent spectral response; bulk GaAs absorption edge; carrier transport; charge collection efficiency; electron thermal escape rate; ground state carrier; ground state electron activation energy; hole tunneling; low temperature bias photocurrent; low temperature photocurrent measurements; optical study; optical transitions; p-n direction; self-assembled quantum dot solar cells; size 870 nm; structure simulations; temperature 20 K; temperature dependent photoluminescence spectroscopy; test structures; tunneling rate; voltage -4.5 V; voltage 0.7 V; Gallium arsenide; Land surface temperature; Photovoltaic cells; Quantum dots; Temperature dependence; Temperature measurement; Tunneling; Carrier collection efficiency; InAs/GaAs quantum dots; Photoluminescence; Thermal escape rate; Tunneling rate; photovoltaic cells;
Conference_Titel :
Photovoltaic Specialists Conference (PVSC), 2013 IEEE 39th
Conference_Location :
Tampa, FL
DOI :
10.1109/PVSC.2013.6744145