TY - JOUR
T1 - Carrier lifetime and charge separation in K+-doped CZTS nanocrystals
AU - Mondal, Animesh
AU - Scheinert, Christopher
AU - Radich, James G.
N1 - Funding Information:
The authors acknowledge Dr. Carlos Carrero and Jorge Moncada for their assistance in collecting and interpreting Raman spectra, Dr. Bruce Tatarchuk and Mingyang Chi for the XPS spectra, Dr. Mehmet Zeki Billor for the XRF spectra on CZTS nanocrystals, and the Auburn University Undergraduate Fellowship Program for supporting work done by C.S. We acknowledge the support by the Auburn University Department of Chemical Engineering for A.M. and the necessary equipment and supplies through J.G.R.’s lab startup funds.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2019/1/28
Y1 - 2019/1/28
N2 - Cu2ZnSnS4 (CZTS) nanocrystals are important materials for next generation solar energy capture and conversion strategies. CZTS contains earth-abundant materials and has optimum band gap energy and high absorption coefficient. However, progress in utilizing CZTS nanocrystals is impeded by the numerous crystal and morphological defects present without high-temperature annealing. These defects commonly result in reduced carrier diffusion length and carrier lifetime. One recent and promising direction for employing CZTS nanocrystals in solar energy capture and conversion strategies is through remediation of defects by doping with alkali earth metal ions such as Li+, Na+, and/or K+. Here we focus on the K+ cationic doping since it has demonstrated the highest efficiencies but without a fundamental investigation into the underlying drivers. We first developed a flexible and reproducible synthesis route to prepare K+-doped CZTS nanocrystals with low polydispersity. We employed undoped and K+-doped nanocrystals to fabricate CZTS photocathodes and evaluated their photoresponsiveness in a photoelectrochemical cell. K+-doped CZTS nanocrystals show the previously reported trend of improved photocurrent density. We obtained further insight into the role of K+ dopant using Raman spectroscopy, X-ray photoelectron spectroscopy, and transient absorption spectroscopy. K+-doping of CZTS nanocrystals boosts charge carrier lifetime and enables better charge extraction efficiency to boost photocurrent. Improved carrier lifetime is attributed to remediation of binary/tertiary impurity phases and surface anion vacancies to yield a higher degree of phase purity and a lower degree of surface electron traps in CZTS.
AB - Cu2ZnSnS4 (CZTS) nanocrystals are important materials for next generation solar energy capture and conversion strategies. CZTS contains earth-abundant materials and has optimum band gap energy and high absorption coefficient. However, progress in utilizing CZTS nanocrystals is impeded by the numerous crystal and morphological defects present without high-temperature annealing. These defects commonly result in reduced carrier diffusion length and carrier lifetime. One recent and promising direction for employing CZTS nanocrystals in solar energy capture and conversion strategies is through remediation of defects by doping with alkali earth metal ions such as Li+, Na+, and/or K+. Here we focus on the K+ cationic doping since it has demonstrated the highest efficiencies but without a fundamental investigation into the underlying drivers. We first developed a flexible and reproducible synthesis route to prepare K+-doped CZTS nanocrystals with low polydispersity. We employed undoped and K+-doped nanocrystals to fabricate CZTS photocathodes and evaluated their photoresponsiveness in a photoelectrochemical cell. K+-doped CZTS nanocrystals show the previously reported trend of improved photocurrent density. We obtained further insight into the role of K+ dopant using Raman spectroscopy, X-ray photoelectron spectroscopy, and transient absorption spectroscopy. K+-doping of CZTS nanocrystals boosts charge carrier lifetime and enables better charge extraction efficiency to boost photocurrent. Improved carrier lifetime is attributed to remediation of binary/tertiary impurity phases and surface anion vacancies to yield a higher degree of phase purity and a lower degree of surface electron traps in CZTS.
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U2 - 10.1021/acsaem.8b01168
DO - 10.1021/acsaem.8b01168
M3 - Article
AN - SCOPUS:85065259079
VL - 2
SP - 250
EP - 259
JO - ACS Applied Energy Materials
JF - ACS Applied Energy Materials
SN - 2574-0962
IS - 1
ER -