Transient Photovoltage Measurements on Perovskite Solar Cells with Varied Defect Concentrations and Inhomogeneous Recombination Rates

Due to the low temperature fabrication process and reduced hysteresis effect, inverted p-i-n structured perovskite solar cells (PSCs) with the PEDOT:PSS as the hole transporting layer and PCBM as the electron transporting layer have attracted considerable attention. However, the energy barrier at the interface between the PCBM layer and the metal electrode, which is due to an energy level mismatch, limits the electron extraction ability. In this work, an inorganic aluminum-doped zinc oxide (AZO) interlayer is inserted between the PCBM layer and the metal electrode so that electrons can be collected efficiently by the electrode. It is shown that with the help of the PCBM/AZO bilayer, the power conversion efficiency of PSCs is significantly improved, with negligible hysteresis and improved device stability. The UPS measurement shows that the AZO interlayer can effectively decrease the energy offset between PCBM and the metal electrode. The steady state photoluminescence, time-resolved photoluminescence, transient photocurrent, and transient photovoltage measurements show that the PSCs with the AZO interlayer have a longer radiative carrier recombination lifetime and more efficient charge extraction efficiency. Moreover, the introduction of the AZO interlayer could protect the underlying perovskite, and thus, greatly improve device stability.

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Origin of Degradation in Perovskite Solar Cells by Intensity Modulated Photovoltage Spectroscopy Measurement (IMVS)

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1028.133 ◽

2021 ◽

Vol 1028 ◽

pp. 133-137

Author(s):

Adhita Asma Nurunnizar ◽

Alvin Fariz ◽

Herman ◽

Rahmat Hidayat

Keyword(s):

Solar Cells ◽

Charge Carrier ◽

Conversion Efficiency ◽

Cell Structure ◽

Perovskite Solar Cells ◽

Nyquist Plot ◽

Frequency Range ◽

Intensity Modulated ◽

Transient Photovoltage ◽

Lower Frequency Range

Perovskite solar cells (PSCs) based on lead halide perovskite have attracted much attention owing to the fast development of their power conversion efficiency (PCE) from 3.8% to 25%. Various factors play important roles in affecting the conversion efficiency of PSCs, such as charge carrier generation, transport, recombination, and collection. In addition, the presence of interfacial defects has also a crucial effect in charge carrier transfer and recombination processes. However, the origin and mechanism of interfacial charge recombinations in PSCs are still not comprehensively investigated. For that purpose, we have performed intensity-modulated photovoltage spectroscopy (IMVS) and transient photovoltage (TPV) measurements of PSCs, which were fabricated with FTO/c-TiO2/mp-TiO2/Perovskite/PTAA/Au cell structure. The solar cell (J-V) characteristics of the PSCs on the day-1, day-2, day-3, and day-6 after the cell fabrication, indicating a significant degradation of the cell with time. The Nyquist plots of IMVS measurement on the same day as the J-V measurement seem to be composed of two semicircles at a lower frequency range and a higher frequency range. The semicircle at the lower frequency range enlarged on the day-6 measurement, but the semicircle at higher frequency decreased. The change of this Nyquist plot is in agreement with a significant decrease in the J-V curves. The semicircle at lower frequency may be assigned to the ion diffusion or migration. Therefore, cell degradation may be caused by the liberation of ions (including iodide) from the surface of the perovskite crystal structure. It then increases recombination loss due to back charge transfer from TiO2 to perovskite as indicated by the changing of the semicircle at high frequency into a smaller semicircle. Therefore, the present results reemphasize that the improvement of PSC stability needs the prevention of ions liberations from the surface by introducing passivation substances. In addition, the results also show the practical usefulness of IMVS for inspecting PSC degradation due to such an ion liberation process.

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Exclusion of metal oxide by an RF sputtered Ti layer in flexible perovskite solar cells: energetic interface between a Ti layer and an organic charge transporting layer

Dalton Transactions ◽

10.1039/c4dt03920c ◽

2015 ◽

Vol 44 (14) ◽

pp. 6439-6448 ◽

Cited By ~ 24

Author(s):

Sadia Ameen ◽

M. Shaheer Akhtar ◽

Hyung-Kee Seo ◽

Mohammad Khaja Nazeeruddin ◽

Hyung-Shik Shin

Keyword(s):

Solar Cells ◽

Metal Oxide ◽

Charge Transport ◽

Perovskite Solar Cells ◽

Recombination Rates

The effects of a titanium (Ti) layer on the charge transport and recombination rates of flexible perovskite solar cells were studied.

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Interfacial recombination kinetics in aged perovskite solar cells measured using transient photovoltage techniques

Nanoscale ◽

10.1039/c9nr06278e ◽

2019 ◽

Vol 11 (42) ◽

pp. 20024-20029 ◽

Cited By ~ 3

Author(s):

Jesús Jiménez-López ◽

Emilio Palomares

Keyword(s):

Solar Cells ◽

Perovskite Solar Cells ◽

Charge Recombination ◽

Transient Photovoltage ◽

Interfacial Recombination ◽

Recombination Kinetics ◽

Interfacial Charge

The reduction of interfacial charge recombination kinetics in perovskite solar cells is key to increase device photovoltaic efficiencies.

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Developments on Perovskite Solar Cells (PSCs): A Critical Review

Applied Sciences ◽

10.3390/app12020672 ◽

2022 ◽

Vol 12 (2) ◽

pp. 672

Author(s):

Lehlohonolo P. Lekesi ◽

Lehlohonolo F. Koao ◽

Setumo V. Motloung ◽

Tshwafo E. Motaung ◽

Thembinkosi Malevu

Keyword(s):

Solar Cells ◽

Active Material ◽

Perovskite Solar Cells ◽

Environmental Concerns ◽

Solar Cell Device ◽

Recombination Rates ◽

Device Architecture ◽

Perovskite Crystal ◽

Low Charge ◽

Improve Device

This review provides detailed information on perovskite solar cell device background and monitors stepwise scientific efforts applied to improve device performance with time. The work reviews previous studies and the latest developments in the perovskite crystal structure, electronic structure, device architecture, fabrication methods, and challenges. Advantages, such as easy bandgap tunability, low charge recombination rates, and low fabrication cost, are among the topics discussed. Some of the most important elements highlighted in this review are concerns regarding commercialization and prototyping. Perovskite solar cells are generally still lab-based devices suffering from drawbacks such as device intrinsic and extrinsic instabilities and rising environmental concerns due to the use of the toxic inorganic lead (Pb) element in the perovskite (ABX3) light-active material. Some interesting recommendations and possible future perspectives are well articulated.

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Unravelling steady-state bulk recombination dynamics in thick efficient vacuum-deposited perovskite solar cells by transient methods

Journal of Materials Chemistry A ◽

10.1039/c9ta04367e ◽

2019 ◽

Vol 7 (24) ◽

pp. 14712-14722 ◽

Cited By ~ 13

Author(s):

David Kiermasch ◽

Lidón Gil-Escrig ◽

Andreas Baumann ◽

Henk J. Bolink ◽

Vladimir Dyakonov ◽

...

Keyword(s):

Solar Cells ◽

Steady State ◽

Perovskite Solar Cells ◽

Second Order ◽

Operational Conditions ◽

Transient Photovoltage ◽

Transient Methods ◽

Charge Extraction ◽

First Time ◽

Recombination Dynamics

By evaluating perovskite solar cells up to 820 nm thick using charge extraction and transient photovoltage, first and second order recombination dynamics can for the first time be identified under operational conditions in complete devices.

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Perovskite CH3NH3PbI3–XClx Solar Cells and their Degradation (Part 1: A Short Review)

Latvian Journal of Physics and Technical Sciences ◽

10.2478/lpts-2021-0005 ◽

2021 ◽

Vol 58 (1) ◽

pp. 44-52

Author(s):

I. Kaulachs ◽

A. Ivanova ◽

A. Tokmakov ◽

M. Roze ◽

I. Mihailovs ◽

...

Keyword(s):

Solar Cells ◽

Perovskite Solar Cells ◽

Life Time ◽

Short Review ◽

Binding Energies ◽

Ambient Conditions ◽

Recombination Rates ◽

High Power Conversion Efficiency ◽

And Diffusion ◽

Carrier Life Time

AbstractDevelopment of hybrid organic-inorganic perovskite solar cells (PSC) has been one of the hottest research topics since 2013. Within brief literature review, we would like to achieve two objectives. Firstly, we would like to indicate that a whole set of physical properties, such as high change carrier mobility, very low recombination rates, large carrier life time and diffusion length, large absorption coefficients and very weak exciton binding energies, are defining high power conversion efficiency (PCE) of methyl ammonium lead trihalide SC. The second objective is to draw attention to some, in our opinion, important aspects that previously have not been satisfactory addressed in literature. Although degradation of PSC is widely discussed, processes at very first exposure to ambient conditions after deposition of top electrode are uncovered.

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Revealing the charge carrier kinetics in perovskite solar cells affected by mesoscopic structures and defect states from simple transient photovoltage measurements

Scientific Reports ◽

10.1038/s41598-020-74603-x ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Rahmat Hidayat ◽

Adhita Asma Nurunnizar ◽

Alvin Fariz ◽

Herman ◽

Erlyta Septa Rosa ◽

...

Keyword(s):

Solar Cells ◽

Short Interval ◽

Perovskite Solar Cells ◽

Crystal Defects ◽

Transport Layer ◽

Time Range ◽

Trap States ◽

Defect States ◽

Perovskite Layer ◽

Transient Photovoltage

Abstract This report shows that, by using simple transient photovoltage (TPV) measurements, we can reveal a significant correlation between the TPV decay characteristics and the performance of these perovskite solar cells. TPV decay seems to be composed of a rising part in a short interval after photoexcitation and a long decaying part that extends up to tens of milliseconds. These decay behaviors look different depending on the mesoscopic structures and the perovskite morphology formed therein, as seen from their Scanning Electron Microcopy images and X-ray diffraction patterns. The decay part can be fitted with a three-exponential decay, which reflects different kinetics of electrons in the perovskite/TiO2 layer. On the other hand, the rising part must be fit by a decay equation derived by employing the convolution theorem, where the rising part can be assigned to the electron transport process inside the perovskite layer and the decaying part can be assigned to electron back-transfer. The characteristics can be then understood by considering the effect of crystal defects and trap states in the perovskite grains and perovskite interface with its transport layer, which is TiO2 in this study. Although the TPV decay occurs in a time range much longer than the primary process of photoexcitation as commonly observed in transient photoluminescence spectroscopy, the processes involved in this TPV strongly correlates with the performance of these perovskite solar cells.

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