TY - JOUR
T1 - Trapping and Detrapping in Colloidal Perovskite Nanoplatelets
T2 - Elucidation and Prevention of Nonradiative Processes through Chemical Treatment
AU - Vonk, Sander J.W.
AU - Fridriksson, Magnus B.
AU - Hinterding, Stijn O.M.
AU - Mangnus, Mark J.J.
AU - Van Swieten, Thomas P.
AU - Grozema, Ferdinand C.
AU - Rabouw, Freddy T.
AU - Van Der Stam, Ward
PY - 2020
Y1 - 2020
N2 - Metal-halide perovskite nanocrystals show promise as the future active material in photovoltaics, lighting, and other optoelectronic applications. The appeal of these materials is largely due to the robustness of the optoelectronic properties to structural defects. The photoluminescence quantum yield (PLQY) of most types of perovskite nanocrystals is nevertheless below unity, evidencing the existence of nonradiative charge-carrier decay channels. In this work, we experimentally elucidate the nonradiative pathways in CsPbBr3 nanoplatelets, before and after chemical treatment with PbBr2 that improves the PLQY. A combination of picosecond streak camera and nanosecond time-correlated single-photon counting measurements is used to probe the excited-state dynamics over 6 orders of magnitude in time. We find that up to 40% of the nanoplatelets from a synthesis batch are entirely nonfluorescent and cannot be turned fluorescent through chemical treatment. The other nanoplatelets show fluorescence, but charge-carrier trapping leads to losses that are prevented by chemical treatment. Interestingly, even without chemical treatment, some losses due to trapping are mitigated because trapped carriers spontaneously detrap on nanosecond-to-microsecond timescales. Our analysis shows that multiple nonradiative pathways are active in perovskite nanoplatelets, which are affected differently by chemical treatment with PbBr2. More generally, our work highlights that in-depth studies using a combination of techniques are necessary to understand nonradiative pathways in fluorescent nanocrystals. Such understanding is essential to optimize synthesis and treatment procedures.
AB - Metal-halide perovskite nanocrystals show promise as the future active material in photovoltaics, lighting, and other optoelectronic applications. The appeal of these materials is largely due to the robustness of the optoelectronic properties to structural defects. The photoluminescence quantum yield (PLQY) of most types of perovskite nanocrystals is nevertheless below unity, evidencing the existence of nonradiative charge-carrier decay channels. In this work, we experimentally elucidate the nonradiative pathways in CsPbBr3 nanoplatelets, before and after chemical treatment with PbBr2 that improves the PLQY. A combination of picosecond streak camera and nanosecond time-correlated single-photon counting measurements is used to probe the excited-state dynamics over 6 orders of magnitude in time. We find that up to 40% of the nanoplatelets from a synthesis batch are entirely nonfluorescent and cannot be turned fluorescent through chemical treatment. The other nanoplatelets show fluorescence, but charge-carrier trapping leads to losses that are prevented by chemical treatment. Interestingly, even without chemical treatment, some losses due to trapping are mitigated because trapped carriers spontaneously detrap on nanosecond-to-microsecond timescales. Our analysis shows that multiple nonradiative pathways are active in perovskite nanoplatelets, which are affected differently by chemical treatment with PbBr2. More generally, our work highlights that in-depth studies using a combination of techniques are necessary to understand nonradiative pathways in fluorescent nanocrystals. Such understanding is essential to optimize synthesis and treatment procedures.
KW - Quantum yield
KW - Excitons
KW - Physical chemical processes
KW - Electrical conductivity
KW - Recombination
UR - http://www.scopus.com/inward/record.url?scp=85084036259&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.0c02287
DO - 10.1021/acs.jpcc.0c02287
M3 - Article
AN - SCOPUS:85084036259
SN - 1932-7447
VL - 124
SP - 8047
EP - 8054
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 14
ER -