The organic-inorganic hybrid perovskite CH3NH3PbI3 has attracted significant interest for its high performance in converting solar light into electrical power with an efficiency exceeding 20%. Unfortunately, chemical ...The organic-inorganic hybrid perovskite CH3NH3PbI3 has attracted significant interest for its high performance in converting solar light into electrical power with an efficiency exceeding 20%. Unfortunately, chemical stability is one major challenge in the development of CH3NH3PbI3 solar cells. It was commonly assumed that moisture or oxygen in the environment causes the poor stability of hybrid halide perovskites, however, here we show from the first-principles calculations that the room-temperature tetragonal phase of CH3NH3PbI3 is thermodynamically unstable with respect to the phase separation into CH3NH3I ＋ PbI2, i.e., the disproportionation is exothermic, independent of the humidity or oxygen in the atmosphere. When the structure is distorted to the low-temperature orthorhombie phase, the energetic cost of separation increases, but remains small. Contributions from vibrational and configurational entropy at room temperature have been considered, but the instability of CH3NH3PbI3 is unchanged. When I is replaced by Br or CI, Pb by Sn, or the organic cation CH3NH3 by inorganic Cs, the perovskites become more stable and do not phase-separate spontaneously. Our study highlights that the poor chemical stability is intrinsic to CH3NH3PbI3 and suggests that element-substitution may solve the chemical stability problem in hybrid halide perovskite solar cells.展开更多
We fabricate nano-structural metal films to improve photoluminescence of perovskite films. When the perovskite film is placed on an ammonia-treated alumina film, stronger photoluminescence is found due to local field ...We fabricate nano-structural metal films to improve photoluminescence of perovskite films. When the perovskite film is placed on an ammonia-treated alumina film, stronger photoluminescence is found due to local field en- hancement effects. In addition, the oxide spacer layer between the metal （e.g., AI, Ag and Au） substrate and the perovskite film plays an important role. The simulations and experiments imply that the enhancement is related to surface plasmons of nano-structural metals.展开更多
The effect of the distribution of organic cations CH3NH3^＋（MA^＋） on the stability,electronic structures and optical properties of CH3NH3 Pb I3 perovskite have been investigated using the plane-wave ultrasoft pseuu...The effect of the distribution of organic cations CH3NH3^＋（MA^＋） on the stability,electronic structures and optical properties of CH3NH3 Pb I3 perovskite have been investigated using the plane-wave ultrasoft pseuudopotentials. Generalized gradient approximation and local density approximation are used to optimize the geometries of six models, which are different in the orientation of organic cations. The results show that model C is more stable than others, and the main contribution to the top of valence band is from I 5p states. In the bottom of conduction bands, the main components are Pb 6s states with an overlapping of I 5p states. When the orientation of organic group is transforming, the Pb I6 octahedra will distort and the band structure will alter with it, which affect the generation and migration of photon-generated carriers and optical properties.展开更多
Organic-inorganic hybrid perovskite materials have been receiving considerable attention due to their promising applications in many optoelectronic fields. However, the optical bandgap of CH3NH3PbI3 perovskite is stil...Organic-inorganic hybrid perovskite materials have been receiving considerable attention due to their promising applications in many optoelectronic fields. However, the optical bandgap of CH3NH3PbI3 perovskite is still disputed. In order to comprehend the intrinsic characteristics of these materials, we study the near-band-edge optical responses of the solution-processed CH3NH3PbI3 perovskite crystals by photoconductivity and reflectance spectroscopy at room temperature. All these spectra of the CH3NH3PbI3 polycrystals show only one significant absorption edge at 1.58 eV. However, we observe an extra absorption edge at 1.47 eV in CH3NH3PbI3 single crystal. We establish a simple kinetic model of charge annihilation processes to explain why the low-energy structure of the photoconductivity and diffuse reflectance spectra of CH3NH3PbI3 polyerystals disappear, which provides another possibility for understanding the difference in absorption edge. It is noteworthy that this low-energy absorption edge of CH3NH3PbI3 single crystal has, to the best of our knowledge, seldom been reported on organic-inorganic hybrid perovskites. Therefore, the CH3NH3PbI3 single crystal exhibits a relatively wide absorption which makes it a promising candidate for photoelectric applications.展开更多
Both of planar and mesoporous architectures prevail for perovskite solar cells(PSCs).However,it is still an open question how the architecture affects the performance of PSCs.The inconsistent results in the references...Both of planar and mesoporous architectures prevail for perovskite solar cells(PSCs).However,it is still an open question how the architecture affects the performance of PSCs.The inconsistent results in the references often create confusion.In particular,the specific roles of mesoporous frameworks are yet to be well elaborated and require further clarification.In this study,we carefully compared the properties of perovskite films and the device performances for both architectures to unravel the roles of mesoporous TiO2 framworks in CH3NH3PbI3 PSCs.The detailed characterizations of structural,microscopic,optical and electrical properties revealed that the presence of mesoporous TiO2 framework contributed to enlarged perovskite crystal sizes,enhanced light harvesting,efficient electron extration and suppressed charge recombination.As a result,compared with the planar device,the mesoporous device yielded an improved power conversion efficiency of 18.18%,coupled with a reduced hystersis.This study reveals the benefits of mesoporous TiO2 framework in PSCs and provides the guidance for the design and optimization of architectures for high-performance devices.展开更多
This work explores the use of poly（3- hexylthiophene） （P3HT） modified carbon nanotubes （CNTs@P3HT） for the cathodes of hole transporter free, mesoscopic perovskite （CH3NH3PbI3） solar cells （PSCs）, simultaneo...This work explores the use of poly（3- hexylthiophene） （P3HT） modified carbon nanotubes （CNTs@P3HT） for the cathodes of hole transporter free, mesoscopic perovskite （CH3NH3PbI3） solar cells （PSCs）, simultaneously achieving high-performance, high stability and low-cost PSCs. Here the thin P3HT modifier acts as an electron blocker to inhibit electron transfer into CNTs and a hydrophobic polymer binder to tightly cross-link the CNTs together to compact the carbon electrode film and greatly stabilize the solar cell. On the other hand, the presence of CNTs greatly improve the conductivity of P3HT. By optimizing the concentration of the P3HT modifier （2 mg/mL）, we have improved the power conversion efficiencies （PCEs） of CNTs@P3HT based PSCs up to 13.43% with an average efficiency of 12.54%, which is much higher than the pure CNTs based PSCs （best PCE 10.59%） and the sandwich-type P3HT/CNTs based PSCs （best PCE 9.50%）. In addition, the hysteresis of the CNTs@P3HT based PSCs is remarkably reduced due to the intimate interface between the perovskite and CNTs@P3HT electrodes. Degradation of the CNTs@ P3HT based PSCs is also strongly retarded as compared to cells employing the pure CNTs electrode when exposed to the ambient condition of 20%- 40% humidity.展开更多
基金supported by the Special Funds for Major State Basic ResearchNational Natural Science Foundation of China(NSFC)+6 种基金Project of Shanghai Municipality(16520721600)supported by NSFC under Grant No 91233121Shanghai Rising-Star Program(14QA1401500)CC of ECNUsupported by the Royal Society,the ERC and EPSRC under Grant Nos EP/M009580/1 and EP/K016288/1supported by the National Key Research and Development Program of China under Grant No 2016YFB0700700the National Natural Science Foundation of China under Grant Nos 51672023,11634003 and U1530401
文摘The organic-inorganic hybrid perovskite CH3NH3PbI3 has attracted significant interest for its high performance in converting solar light into electrical power with an efficiency exceeding 20%. Unfortunately, chemical stability is one major challenge in the development of CH3NH3PbI3 solar cells. It was commonly assumed that moisture or oxygen in the environment causes the poor stability of hybrid halide perovskites, however, here we show from the first-principles calculations that the room-temperature tetragonal phase of CH3NH3PbI3 is thermodynamically unstable with respect to the phase separation into CH3NH3I ＋ PbI2, i.e., the disproportionation is exothermic, independent of the humidity or oxygen in the atmosphere. When the structure is distorted to the low-temperature orthorhombie phase, the energetic cost of separation increases, but remains small. Contributions from vibrational and configurational entropy at room temperature have been considered, but the instability of CH3NH3PbI3 is unchanged. When I is replaced by Br or CI, Pb by Sn, or the organic cation CH3NH3 by inorganic Cs, the perovskites become more stable and do not phase-separate spontaneously. Our study highlights that the poor chemical stability is intrinsic to CH3NH3PbI3 and suggests that element-substitution may solve the chemical stability problem in hybrid halide perovskite solar cells.
基金Supported by the Ministry of Science and Technology of China under Grant No 2016YFA0202201the National Natural Science Foundation of China under Grant Nos 61290304,11574335 and 61376016+1 种基金the Youth Innovation Promotion Association of the Chinese Academy of Sciencesthe 333 Project of Jiangsu province under Grant No BRA2017352
文摘We fabricate nano-structural metal films to improve photoluminescence of perovskite films. When the perovskite film is placed on an ammonia-treated alumina film, stronger photoluminescence is found due to local field en- hancement effects. In addition, the oxide spacer layer between the metal （e.g., AI, Ag and Au） substrate and the perovskite film plays an important role. The simulations and experiments imply that the enhancement is related to surface plasmons of nano-structural metals.
基金Supported by the program for National Natural Science Foundation of China(51102150,51472081)Foundation of Hubei University of Technology for High-level Talents(GCRC13014)Development Founds of Hubei Collaborative Innovation Center(HBSKFZD2014003,HBSKFZD2014011,HBSKFZD2015004)
文摘The effect of the distribution of organic cations CH3NH3^＋（MA^＋） on the stability,electronic structures and optical properties of CH3NH3 Pb I3 perovskite have been investigated using the plane-wave ultrasoft pseuudopotentials. Generalized gradient approximation and local density approximation are used to optimize the geometries of six models, which are different in the orientation of organic cations. The results show that model C is more stable than others, and the main contribution to the top of valence band is from I 5p states. In the bottom of conduction bands, the main components are Pb 6s states with an overlapping of I 5p states. When the orientation of organic group is transforming, the Pb I6 octahedra will distort and the band structure will alter with it, which affect the generation and migration of photon-generated carriers and optical properties.
基金supported by the National Natural Science Foundation of China(Grant Nos.11574302,61474114,61674141,61504134,21503209&11704032)the National Basic Research Program of China(Grant Nos.2015CB921503,2014CB643503&2013CB632805)+1 种基金National Key Research and Development Program(Grant Nos.2016YFB0402303&2016YFB0400101)Key Research Program of Frontier Science,Chinese Academy of Sciences(Grant No.QYZDB-SSW-SLH006)
文摘Organic-inorganic hybrid perovskite materials have been receiving considerable attention due to their promising applications in many optoelectronic fields. However, the optical bandgap of CH3NH3PbI3 perovskite is still disputed. In order to comprehend the intrinsic characteristics of these materials, we study the near-band-edge optical responses of the solution-processed CH3NH3PbI3 perovskite crystals by photoconductivity and reflectance spectroscopy at room temperature. All these spectra of the CH3NH3PbI3 polycrystals show only one significant absorption edge at 1.58 eV. However, we observe an extra absorption edge at 1.47 eV in CH3NH3PbI3 single crystal. We establish a simple kinetic model of charge annihilation processes to explain why the low-energy structure of the photoconductivity and diffuse reflectance spectra of CH3NH3PbI3 polyerystals disappear, which provides another possibility for understanding the difference in absorption edge. It is noteworthy that this low-energy absorption edge of CH3NH3PbI3 single crystal has, to the best of our knowledge, seldom been reported on organic-inorganic hybrid perovskites. Therefore, the CH3NH3PbI3 single crystal exhibits a relatively wide absorption which makes it a promising candidate for photoelectric applications.
基金financially supported by the National Natural Science Foundation of China(51602088)the Open Fund of the Key Laboratory of Photovoltaic and Energy Conservation Materials,Chinese Academy of Sciences(PECL2019KF007)and China Postdoctoral Science Foundation(2017T100313)。
文摘Both of planar and mesoporous architectures prevail for perovskite solar cells(PSCs).However,it is still an open question how the architecture affects the performance of PSCs.The inconsistent results in the references often create confusion.In particular,the specific roles of mesoporous frameworks are yet to be well elaborated and require further clarification.In this study,we carefully compared the properties of perovskite films and the device performances for both architectures to unravel the roles of mesoporous TiO2 framworks in CH3NH3PbI3 PSCs.The detailed characterizations of structural,microscopic,optical and electrical properties revealed that the presence of mesoporous TiO2 framework contributed to enlarged perovskite crystal sizes,enhanced light harvesting,efficient electron extration and suppressed charge recombination.As a result,compared with the planar device,the mesoporous device yielded an improved power conversion efficiency of 18.18%,coupled with a reduced hystersis.This study reveals the benefits of mesoporous TiO2 framework in PSCs and provides the guidance for the design and optimization of architectures for high-performance devices.
文摘This work explores the use of poly（3- hexylthiophene） （P3HT） modified carbon nanotubes （CNTs@P3HT） for the cathodes of hole transporter free, mesoscopic perovskite （CH3NH3PbI3） solar cells （PSCs）, simultaneously achieving high-performance, high stability and low-cost PSCs. Here the thin P3HT modifier acts as an electron blocker to inhibit electron transfer into CNTs and a hydrophobic polymer binder to tightly cross-link the CNTs together to compact the carbon electrode film and greatly stabilize the solar cell. On the other hand, the presence of CNTs greatly improve the conductivity of P3HT. By optimizing the concentration of the P3HT modifier （2 mg/mL）, we have improved the power conversion efficiencies （PCEs） of CNTs@P3HT based PSCs up to 13.43% with an average efficiency of 12.54%, which is much higher than the pure CNTs based PSCs （best PCE 10.59%） and the sandwich-type P3HT/CNTs based PSCs （best PCE 9.50%）. In addition, the hysteresis of the CNTs@P3HT based PSCs is remarkably reduced due to the intimate interface between the perovskite and CNTs@P3HT electrodes. Degradation of the CNTs@ P3HT based PSCs is also strongly retarded as compared to cells employing the pure CNTs electrode when exposed to the ambient condition of 20%- 40% humidity.
