TY  - JOUR
A1  - García-Benito, Inés
A1  - Quarti, Claudio
A1  - Queloz, Valentin I. E.
A1  - Hofstetter, Yvonne J.
A1  - Becker-Koch, David
A1  - Caprioglio, Pietro
A1  - Neher, Dieter
A1  - Orlandi, Simonetta
A1  - Cavazzini, Marco
A1  - Pozzi, Gianluca
A1  - Even, Jacky
A1  - Nazeeruddin, Mohammad Khaja
A1  - Vaynzof, Yana
A1  - Grancini, Giulia
T1  - Fluorination of organic spacer impacts on the structural and optical response of 2D perovskites
JF  - Frontiers in Chemistry
N2  - Low-dimensional hybrid perovskites have triggered significant research interest due to their intrinsically tunable optoelectronic properties and technologically relevant material stability. In particular, the role of the organic spacer on the inherent structural and optical features in two-dimensional (2D) perovskites is paramount for material optimization. To obtain a deeper understanding of the relationship between spacers and the corresponding 2D perovskite film properties, we explore the influence of the partial substitution of hydrogen atoms by fluorine in an alkylammonium organic cation, resulting in (Lc)(2)PbI4 and (Lf)(2)PbI4 2D perovskites, respectively. Consequently, optical analysis reveals a clear 0.2 eV blue-shift in the excitonic position at room temperature. This result can be mainly attributed to a band gap opening, with negligible effects on the exciton binding energy. According to Density Functional Theory (DFT) calculations, the band gap increases due to a larger distortion of the structure that decreases the atomic overlap of the wavefunctions and correspondingly bandwidth of the valence and conduction bands. In addition, fluorination impacts the structural rigidity of the 2D perovskite, resulting in a stable structure at room temperature and the absence of phase transitions at a low temperature, in contrast to the widely reported polymorphism in some non-fluorinated materials that exhibit such a phase transition. This indicates that a small perturbation in the material structure can strongly influence the overall structural stability and related phase transition of 2D perovskites, making them more robust to any phase change. This work provides key information on how the fluorine content in organic spacer influence the structural distortion of 2D perovskites and their optical properties which possess remarkable importance for future optoelectronic applications, for instance in the field of light-emitting devices or sensors.
KW  - fluorinated organic spacer
KW  - 2D perovskites
KW  - phase transition
KW  - temperature dependence
KW  - excitonic materials
Y1  - 2020
U6  - https://doi.org/10.3389/fchem.2019.00946
SN  - 2296-2646
VL  - 7
SP  - 1
EP  - 11
PB  - Frontiers Media
CY  - Lausanne
ER  - 
TY  - GEN
A1  - García-Benito, Inés
A1  - Quarti, Claudio
A1  - Queloz, Valentin I. E.
A1  - Hofstetter, Yvonne J.
A1  - Becker-Koch, David
A1  - Caprioglio, Pietro
A1  - Neher, Dieter
A1  - Orlandi, Simonetta
A1  - Cavazzini, Marco
A1  - Pozzi, Gianluca
A1  - Even, Jacky
A1  - Nazeeruddin, Mohammad Khaja
A1  - Vaynzof, Yana
A1  - Grancini, Giulia
T1  - Fluorination of organic spacer impacts on the structural and optical response of 2D perovskites
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Low-dimensional hybrid perovskites have triggered significant research interest due to their intrinsically tunable optoelectronic properties and technologically relevant material stability. In particular, the role of the organic spacer on the inherent structural and optical features in two-dimensional (2D) perovskites is paramount for material optimization. To obtain a deeper understanding of the relationship between spacers and the corresponding 2D perovskite film properties, we explore the influence of the partial substitution of hydrogen atoms by fluorine in an alkylammonium organic cation, resulting in (Lc)(2)PbI4 and (Lf)(2)PbI4 2D perovskites, respectively. Consequently, optical analysis reveals a clear 0.2 eV blue-shift in the excitonic position at room temperature. This result can be mainly attributed to a band gap opening, with negligible effects on the exciton binding energy. According to Density Functional Theory (DFT) calculations, the band gap increases due to a larger distortion of the structure that decreases the atomic overlap of the wavefunctions and correspondingly bandwidth of the valence and conduction bands. In addition, fluorination impacts the structural rigidity of the 2D perovskite, resulting in a stable structure at room temperature and the absence of phase transitions at a low temperature, in contrast to the widely reported polymorphism in some non-fluorinated materials that exhibit such a phase transition. This indicates that a small perturbation in the material structure can strongly influence the overall structural stability and related phase transition of 2D perovskites, making them more robust to any phase change. This work provides key information on how the fluorine content in organic spacer influence the structural distortion of 2D perovskites and their optical properties which possess remarkable importance for future optoelectronic applications, for instance in the field of light-emitting devices or sensors.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1421 
KW  - fluorinated organic spacer
KW  - 2D perovskites
KW  - phase transition
KW  - temperature dependence
KW  - excitonic materials
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-512420
SN  - 1866-8372
ER  - 
TY  - GEN
A1  - Wolff, Christian Michael
A1  - Canil, Laura
A1  - Rehermann, Carolin
A1  - Nguyen, Ngoc Linh
A1  - Zu, Fengshuo
A1  - Ralaiarisoa, Maryline
A1  - Caprioglio, Pietro
A1  - Fiedler, Lukas
A1  - Stolterfoht, Martin
A1  - Kogikoski, Junior, Sergio
A1  - Bald, Ilko
A1  - Koch, Norbert
A1  - Unger, Eva L.
A1  - Dittrich, Thomas
A1  - Abate, Antonio
A1  - Neher, Dieter
T1  - Correction to 'Perfluorinated self-assembled monolayers enhance the stability and efficiency of inverted perovskite solar cells' (2020, 14 (2), 1445−1456)
T2  - ACS nano
Y1  - 2020
U6  - https://doi.org/10.1021/acsnano.0c08081
SN  - 1936-0851
SN  - 1936-086X
VL  - 14
IS  - 11
SP  - 16156
EP  - 16156
PB  - American Chemical Society
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Wang, Qiong
A1  - Smith, Joel A.
A1  - Skroblin, Dieter
A1  - Steele, Julian A.
A1  - Wolff, Christian Michael
A1  - Caprioglio, Pietro
A1  - Stolterfoht, Martin
A1  - Köbler, Hans
A1  - Turren-Cruz, Silver-Hamill
A1  - Li, Meng
A1  - Gollwitzer, Christian
A1  - Neher, Dieter
A1  - Abate, Antonio
T1  - Managing phase purities and crystal orientation for high-performance and photostable cesium lead halide perovskite solar cells
JF  - Solar RRL
N2  - Inorganic perovskites with cesium (Cs+) as the cation have great potential as photovoltaic materials if their phase purity and stability can be addressed. Herein, a series of inorganic perovskites is studied, and it is found that the power conversion efficiency of solar cells with compositions CsPbI1.8Br1.2, CsPbI2.0Br1.0, and CsPbI2.2Br0.8 exhibits a high dependence on the initial annealing step that is found to significantly affect the crystallization and texture behavior of the final perovskite film. At its optimized annealing temperature, CsPbI1.8Br1.2 exhibits a pure orthorhombic phase and only one crystal orientation of the (110) plane. Consequently, this allows for the best efficiency of up to 14.6% and the longest operational lifetime, T-S80, of approximate to 300 h, averaged of over six solar cells, during the maximum power point tracking measurement under continuous light illumination and nitrogen atmosphere. This work provides essential progress on the enhancement of photovoltaic performance and stability of CsPbI3 - xBrx perovskite solar cells.
KW  - cesium lead halides
KW  - crystal orientation
KW  - inorganic perovskites
KW  - ISOS-L-1I protocol
KW  - phase purity
KW  - photostability
Y1  - 2020
VL  - 4
IS  - 9
PB  - WILEY-VCH
CY  - Weinheim
ER  - 
TY  - GEN
A1  - Schulze, Patricia S. C.
A1  - Bett, Alexander J.
A1  - Bivour, Martin
A1  - Caprioglio, Pietro
A1  - Gerspacher, Fabian M.
A1  - Kabaklı, Özde Ş.
A1  - Richter, Armin
A1  - Stolterfoht, Martin
A1  - Zhang, Qinxin
A1  - Neher, Dieter
A1  - Hermle, Martin
A1  - Hillebrecht, Harald
A1  - Glunz, Stefan W.
A1  - Goldschmidt, Jan Christoph
T1  - 25.1% high-efficiency monolithic perovskite silicon tandem solar cell with a high bandgap perovskite absorber
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 eV in planar p-i-n tandem configuration. A methylammonium-free FA(0.75)Cs(0.25)Pb(I0.8Br0.2)(3) perovskite with high Cs content is investigated for improved stability. A 10% molarity increase to 1.1 m of the perovskite precursor solution results in approximate to 75 nm thicker absorber layers and 0.7 mA cm(-2) higher short-circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80% and up to 25.1% certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3% (absolute) over 5 months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30% tandem efficiency in the near future.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1197 
KW  - heterojunction silicon solar cells
KW  - interfaces
KW  - perovskite solar cells
KW  - tandem solar cells
KW  - thin films
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-525668
SN  - 1866-8372
IS  - 7
ER  - 
TY  - JOUR
A1  - Schulze, Patricia S. C.
A1  - Bett, Alexander J.
A1  - Bivour, Martin
A1  - Caprioglio, Pietro
A1  - Gerspacher, Fabian M.
A1  - Kabaklı, Özde Ş.
A1  - Richter, Armin
A1  - Stolterfoht, Martin
A1  - Zhang, Qinxin
A1  - Neher, Dieter
A1  - Hermle, Martin
A1  - Hillebrecht, Harald
A1  - Glunz, Stefan W.
A1  - Goldschmidt, Jan Christoph
T1  - 25.1% high-efficiency monolithic perovskite silicon tandem solar cell with a high bandgap perovskite absorber
JF  - Solar RRL
N2  - Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 eV in planar p-i-n tandem configuration. A methylammonium-free FA(0.75)Cs(0.25)Pb(I0.8Br0.2)(3) perovskite with high Cs content is investigated for improved stability. A 10% molarity increase to 1.1 m of the perovskite precursor solution results in approximate to 75 nm thicker absorber layers and 0.7 mA cm(-2) higher short-circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80% and up to 25.1% certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3% (absolute) over 5 months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30% tandem efficiency in the near future.
KW  - heterojunction silicon solar cells
KW  - interfaces
KW  - perovskite solar cells
KW  - tandem solar cells
KW  - thin films
Y1  - 2020
VL  - 4
IS  - 7
PB  - John Wiley & Sons, Inc.
CY  - New Jersey
ER  - 
TY  - GEN
A1  - Stolterfoht, Martin
A1  - Grischek, Max
A1  - Caprioglio, Pietro
A1  - Wolff, Christian Michael
A1  - Gutierrez-Partida, Emilio
A1  - Peña-Camargo, Francisco
A1  - Rothhardt, Daniel
A1  - Zhang, Shanshan
A1  - Raoufi, Meysam
A1  - Wolansky, Jakob
A1  - Abdi-Jalebi, Mojtaba
A1  - Stranks, Samuel D.
A1  - Albrecht, Steve
A1  - Kirchartz, Thomas
A1  - Neher, Dieter
T1  - How to quantify the efficiency potential of neat perovskite films
BT  - Perovskite semiconductors with an implied efficiency exceeding 28%
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Perovskite photovoltaic (PV) cells have demonstrated power conversion efficiencies (PCE) that are close to those of monocrystalline silicon cells; however, in contrast to silicon PV, perovskites are not limited by Auger recombination under 1-sun illumination. Nevertheless, compared to GaAs and monocrystalline silicon PV, perovskite cells have significantly lower fill factors due to a combination of resistive and non-radiative recombination losses. This necessitates a deeper understanding of the underlying loss mechanisms and in particular the ideality factor of the cell. By measuring the intensity dependence of the external open-circuit voltage and the internal quasi-Fermi level splitting (QFLS), the transport resistance-free efficiency of the complete cell as well as the efficiency potential of any neat perovskite film with or without attached transport layers are quantified. Moreover, intensity-dependent QFLS measurements on different perovskite compositions allows for disentangling of the impact of the interfaces and the perovskite surface on the non-radiative fill factor and open-circuit voltage loss. It is found that potassium-passivated triple cation perovskite films stand out by their exceptionally high implied PCEs > 28%, which could be achieved with ideal transport layers. Finally, strategies are presented to reduce both the ideality factor and transport losses to push the efficiency to the thermodynamic limit.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1434 
KW  - non-radiative interface recombination
KW  - perovskite solar cells
KW  - photoluminescence
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-516622
SN  - 1866-8372
IS  - 17
ER  - 
TY  - JOUR
A1  - Stolterfoht, Martin
A1  - Grischek, Max
A1  - Caprioglio, Pietro
A1  - Wolff, Christian Michael
A1  - Gutierrez-Partida, Emilio
A1  - Peña-Camargo, Francisco
A1  - Rothhardt, Daniel
A1  - Zhang, Shanshan
A1  - Raoufi, Meysam
A1  - Wolansky, Jakob
A1  - Abdi-Jalebi, Mojtaba
A1  - Stranks, Samuel D.
A1  - Albrecht, Steve
A1  - Kirchartz, Thomas
A1  - Neher, Dieter
T1  - How to quantify the efficiency potential of neat perovskite films
BT  - Perovskite semiconductors with an implied efficiency exceeding 28%
JF  - Advanced Materials
N2  - Perovskite photovoltaic (PV) cells have demonstrated power conversion efficiencies (PCE) that are close to those of monocrystalline silicon cells; however, in contrast to silicon PV, perovskites are not limited by Auger recombination under 1-sun illumination. Nevertheless, compared to GaAs and monocrystalline silicon PV, perovskite cells have significantly lower fill factors due to a combination of resistive and non-radiative recombination losses. This necessitates a deeper understanding of the underlying loss mechanisms and in particular the ideality factor of the cell. By measuring the intensity dependence of the external open-circuit voltage and the internal quasi-Fermi level splitting (QFLS), the transport resistance-free efficiency of the complete cell as well as the efficiency potential of any neat perovskite film with or without attached transport layers are quantified. Moreover, intensity-dependent QFLS measurements on different perovskite compositions allows for disentangling of the impact of the interfaces and the perovskite surface on the non-radiative fill factor and open-circuit voltage loss. It is found that potassium-passivated triple cation perovskite films stand out by their exceptionally high implied PCEs > 28%, which could be achieved with ideal transport layers. Finally, strategies are presented to reduce both the ideality factor and transport losses to push the efficiency to the thermodynamic limit.
KW  - non-radiative interface recombination
KW  - perovskite solar cells
KW  - photoluminescence
Y1  - 2020
U6  - https://doi.org/10.1002/adma.202000080
SN  - 0935-9648
SN  - 1521-4095
VL  - 32
IS  - 17
SP  - 1
EP  - 10
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - GEN
A1  - Wang, Qiong
A1  - Smith, Joel A.
A1  - Skroblin, Dieter
A1  - Steele, Julian A.
A1  - Wolff, Christian Michael
A1  - Caprioglio, Pietro
A1  - Stolterfoht, Martin
A1  - Köbler, Hans
A1  - Turren-Cruz, Silver-Hamill
A1  - Li, Meng
A1  - Gollwitzer, Christian
A1  - Neher, Dieter
A1  - Abate, Antonio
T1  - Managing phase purities and crystal orientation for high-performance and photostable cesium lead halide perovskite solar cells
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Inorganic perovskites with cesium (Cs+) as the cation have great potential as photovoltaic materials if their phase purity and stability can be addressed. Herein, a series of inorganic perovskites is studied, and it is found that the power conversion efficiency of solar cells with compositions CsPbI1.8Br1.2, CsPbI2.0Br1.0, and CsPbI2.2Br0.8 exhibits a high dependence on the initial annealing step that is found to significantly affect the crystallization and texture behavior of the final perovskite film. At its optimized annealing temperature, CsPbI1.8Br1.2 exhibits a pure orthorhombic phase and only one crystal orientation of the (110) plane. Consequently, this allows for the best efficiency of up to 14.6% and the longest operational lifetime, T-S80, of approximate to 300 h, averaged of over six solar cells, during the maximum power point tracking measurement under continuous light illumination and nitrogen atmosphere. This work provides essential progress on the enhancement of photovoltaic performance and stability of CsPbI3 - xBrx perovskite solar cells.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1210 
KW  - cesium lead halides
KW  - crystal orientation
KW  - inorganic perovskites
KW  - ISOS-L-1I protocol
KW  - phase purity
KW  - photostability
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-525374
SN  - 1866-8372
IS  - 9
ER  -