|
更新情報
PDの張さんの論文
「Photoexcited carrier dynamics in colloidal quantum dot solar cells:
insights into individual quantum dots, quantum dot solid films and devices」
がChemical Society Reviewsの表紙に抜擢されました。
イメージがコチラ
おめでとうございます！
Fig. Photoexcited carrier
dynamics in colloidal quantum dot solar cells
|
Photoexcited carrier
dynamics in colloidal quantum dot solar cells: insights into individual quantum
dots, quantum dot solid films and devices
|
The certified power conversion efficiency (PCE) record of colloidal quantum
dot solar cells (QDSCs) has considerably improved from below 4% to 16.6% in the last few
years. However, the record PCE value of QDSCs is still substantially lower than the
theoretical efficiency. So far, there have been several reviews on recent and significant
achievements in QDSCs, but reviews on photoexcited carrier dynamics in QDSCs are scarce. The
photovoltaic performances of QDSCs are still limited by the photovoltage, photocurrent and
fill factor that are mainly determined by the photoexcited carrier dynamics, including
carrier (or exciton) generation, carrier extraction or transfer, and the carrier
recombination process, in the devices. In this review, the photoexcited carrier dynamics in
the whole QDSCs, originating from individual quantum dots (QDs) to the entire device as well
as the characterization methods used for analyzing the photoexcited carrier dynamics are
summarized and discussed. The recent research including photoexcited multiple exciton
generation (MEG), hot electron extraction, and carrier transfer between adjacent QDs, as
well as carrier injection and recombination at each interface of QDSCs are discussed in
detail herein. The influence of photoexcited carrier dynamics on the physiochemical
properties of QDs and photovoltaic performances of QDSC devices is also discussed.
[See more]
Yaohong Zhang, Guohua Wu, Feng Liu, Chao Ding, Zhigang Zou and Qing
Shen.
|
Fig. Schematic illustration of hot and cold electron and hole relaxation and transfer at the
FAPbI3 QDs/TiO2 and FAPbI3 QDs/NiOx heterojunctions.
|
Photoexcited hot and cold
electron and hole dynamics at FAPbI3 perovskite quantum dots/metal oxide
heterojunctions used for stable perovskite quantum dot solar cells
|
Highly luminescent formamidinium lead iodide (FAPbI3) quantum dots (QDs)
exhibit high stability and narrowest bandgap energy among lead halide perovskites, thus they
have become one of the most promising materials for the development of perovskite QD-based
light-harvesting and near infrared-emitting devices. However, little is known thus far about
photoexcited carrier dynamics at the interface between FAPbI3 QDs and charge transport
layers, which is very important for both fundamental studies and applications of the
QD/charge transport layer heterojunctions. Here, we systematically investigate both hot and
cold photoexcited carrier (electron and hole) dynamics including relaxation and transfer at
the heterojunction interfaces between FAPbI3 QDs and two kinds of well used charge
acceptors, i.e., TiO2 and NiOx. We find that (i) the hot carriers in the FAPbI3 QDs are
cooled to cold carriers with a cooling rate in the order of 1011 s−1, and (ii) the
cold-electron and -hole injection rates are size dependent and are 2.01–2.29 × 109 s−1 and
1.55–1.96 × 109 s−1 at the two types of FAPbI3 QD/MO (metal oxide) heterojunctions,
respectively, which are in good agreements with Marcus theory of charge transfer. In
addition, the photoexcited carrier injection efficiency at the two heterojunctions is found
to be as high as over 99%, which is the most important key for achieving high photovoltaic
performance of the FAPbI3 QD solar cells (QDSCs). Prototypes of the two types of
heterojunction-based QDSCs, i.e., normal-structure solar cells based on FAPbI3 QD/TiO2 and
inverted-structure solar cells based on FAPbI3 QD/NiOx, were developed and the power
conversion efficiencies of more than 9% and 5% were obtained, respectively. Moreover, the
photovoltaic performance showed a higher storage stability over 100 days. The photovoltaic
performance would be improved largely by optimization of each parts in the QDSCs. Our
results shed light on perovskite QD-based optoelectronic devices.
[See more]
Naoki Nakazawa, Yaohong Zhang, Feng Liu, Chao Ding, Kanae Hori, Taro
Toyoda, Yingfang Yao, Yong Zhou, Shuzi Hayase, Ruixiang Wang, Zhigang Zoub and Qing Shen
|
Fig. a)The device structure adopted in this study.
PEAI was used as the passivation layer on the perovskite surface.
b)Cross-sectional SEM images of PEAI-treated perovskite devices.
|
Growth of Amorphous
Passivation Layer Using Phenethylammonium Iodide for High‐Performance Inverted
Perovskite Solar Cells
|
Organic–inorganic lead halide perovskite solar cells have realized a rapid
increase of power conversion efficiency (PCE) in the past few years. However, their
performance still suffers trap‐assisted decline due to defects at the surface and grain
boundaries of the perovskite film. Herein, a phenethylammonium iodide‐lead iodide
(PEAI‐PbI2) passivation layer is formed on the CH3NH3PbI3 perovskite film. The
characterization results indicate that the PEAI covering layer leads to the reduction of
surface defects and suppression of nonradiative recombination. By manipulating this surface
passivation method, a remarkably improved VOC of 1.16 V and an enhanced PCE of 20.8% are
achieved.
[See more]
Fan Zhang, Qinxun Huang, Jun Song, Yaohong Zhang, Chao Ding, Feng Liu,
Dong Liu, Xiaobin Li, Hironobu Yasuda, Koji Yoshida, Junle Qu, Shuzi Hayase,
Taro Toyoda, Takashi Minemoto, and Qing Shen.
|
Fig. (A)Schematic diagram of the architecture of ZnO@SnO2NW-based CQDSCs. (B)The J-V curves of
ZnO NW CQDSCs with or without SnO2 passivation.
|
Improving Photovoltaic
Performance of ZnO Nanowires Based Colloidal Quantum Dot Solar Cells via SnO2
Passivation Strategy
|
Colloidal quantum dot solar cells (CQDSCs) based on one-dimensional metal
oxide nanowires (NWs) as the electron transport layer (ETL) have attracted much attention
due to their larger ETL/colloidal quantum dots (CQDs) contact area and longer electron
transport length than other structure CQDSCs, such as planar CQDSCs. However, it is known
that defect states in NWs would increase the recombination rate because of the high surface
area of NWs. Here, the defect species on the ZnO NWs' surface which resulted in the surface
recombination and SnO2 passivation effects were investigated. Comparing with the solar cells
using pristine ZnO NWs, the CQDSCs based on SnO2 passivated ZnO NW electrodes exhibited a
beneficial band alignment to charge separation, and the interfacial recombination at the
ZnO/CQD interface was reduced, eventually resulting in a 40% improvement of power conversion
efficiency (PCE). Overall, these findings indicate that surface passivation and the
reduction of deep level defects in ETLs could contribute to improving the PCE of CQDSCs.
[See more]
Shuhei Ozu, Yaohong Zhang, Hironobu Yasuda, Yukiko Kitabatake, Taro
Toyoda, Masayuki Hirata, Kenji Yoshino, Kenji Katayama, Shuzi Hayase, Ruixiang Wang and Qing
Shen.
|
|
|
