Transport parameters of perovskite solar cells

30 01 2015

This paper reports an excellent characterization of different tarnsport and recombination parameters of organolead trihalide MAPbX3 (MA = CH3NH3+; X = Br– or I–) single crystals. One important result is the very low density of traps that is infered from space charge limited current measurements

Science 30 January 2015:
Vol. 347 no. 6221 pp. 519-522
DOI: 10.1126/science.aaa2725

Low trap-state density and long carrier diffusion in organolead trihalide perovskite single crystals

  1. Dong Shi1,*,
  2. Valerio Adinolfi2,*,
  3. Riccardo Comin2,
  4. Mingjian Yuan2,
  5. Erkki Alarousu1,
  6. Andrei Buin2,
  7. Yin Chen1,
  8. Sjoerd Hoogland2,
  9. Alexander Rothenberger1,
  10. Khabiboulakh Katsiev1,
  11. Yaroslav Losovyj3,
  12. Xin Zhang4,
  13. Peter A. Dowben4,
  14. Omar F. Mohammed1,
  15. Edward H. Sargent2,
  16. Osman M. Bakr1,

 

The fundamental properties and ultimate performance limits of organolead trihalide MAPbX3 (MA = CH3NH3+; X = Br or I) perovskites remain obscured by extensive disorder in polycrystalline MAPbX3 films. We report an antisolvent vapor-assisted crystallization approach that enables us to create sizable crack-free MAPbX3single crystals with volumes exceeding 100 cubic millimeters. These large single crystals enabled a detailed characterization of their optical and charge transport characteristics. We observed exceptionally low trap-state densities on the order of 109 to 1010 per cubic centimeter in MAPbX3 single crystals (comparable to the best photovoltaic-quality silicon) and charge carrier diffusion lengths exceeding 10 micrometers. These results were validated with density functional theory calculations.

See also>

Electron-hole diffusion lengths >175 μm in solution grown CH3NH3PbI3 single crystals

Qingfeng Dong,

Yanjun Fang,

Yuchuan Shao,

Pahraic Mulligan,

Jie Qiu,

Lei Cao,

and Jinsong Huang

Science aaa5760Published online 29 January 2015

Long, balanced electron and hole diffusion lengths greater than 100 nanometers in polycrystalline CH3NH3PbI3 are critical for highly efficient perovskite solar cells. We report that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 μm under 1 sun illumination and exceed 3 mm under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3 mm-thick single crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, lifetime and dramatically smaller trap densities in the single crystals than polycrystalline thin-films. The long carrier diffusion lengths enabled the use of CH3NH3PbI3 in radiation sensing and energy-harvesting through gammavoltaic effect with an efficiency of 3.9% measured with an intense cesium-137 source.

High-efficiency solution-processed perovskite solar cells with millimeter-scale grains

Wanyi Nie,

 

 





Introducing Perovskite Solar Cells to Undergraduates

16 01 2015

In this Viewpoint, the authors show that it is sufficiently easy and cheap to fabricate a perovskite solar cell that this can be done as an undergraduate laboratory experiment.

Introducing Perovskite Solar Cells to Undergraduates

Sameer Patwardhan , Duyen H. Cao , Shelby Hatch, Omar K. Farha , Joseph T. Hupp , Mercouri G. Kanatzidis , and George C. Schatz

J. Phys. Chem. Lett., 2015, 6, pp 251–255

DOI: 10.1021/jz502648y





Classification of solar cells according to mechanisms of charge separation and charge collection

15 01 2015

Classification of solar cells according to mechanisms of charge separation and charge collection

Thomas Kirchartz,  Juan Bisquert,   Ivan Mora-Sero and  Germà Garcia-Belmonte
Phys. Chem. Chem. Phys., 2015,

DOI: 10.1039/C4CP05174B

In the last decade, photovoltaics (PV) has experienced an important transformation. Traditional solar cells formed by compact semiconductor layers have been joined by new kinds of cells that are constituted by a complex mixture of organic, inorganic and solid or liquid electrolyte materials, and rely on charge separation at the nanoscale. Recently, metal organic halide perovskites have appeared in the photovoltaic landscape showing large conversion efficiencies, and they may share characteristics of the two former types. In this paper we provide a general description of the photovoltaic mechanisms of the single absorber solar cell types, combining all-inorganic, hybrid and organic cells into a single framework. The operation of the solar cell relies on a number of internal processes that exploit internal charge separation and overall charge collection minimizing recombination. There are two main effects to achieve the required efficiency, first to exploit kinetics at interfaces, favouring the required forward process, and second to take advantage of internal electrical fields caused by a built-in voltage and by the distribution of photogenerated charges. These principles represented by selective contacts, interfaces and the main energy diagram, form a solid base for the discussion of the operation of future types of solar cells. Additional effects based on ferroelectric polarization and ionic drift provide interesting prospects for investigating new PV effects mainly in the perovskite materials.

GA




Progress in perovskite solar cells: the dance of anions and cations

7 01 2015

Read the story about the paper published in Nature by Sang Il Seok

Perovskite Solar Cell Bests Bugbears, Reaches Record Efficiency

and see in the paper how they made the 18.9 efficient perovskite solar cell

Compositional engineering of perovskite materials for high-performance solar cell

Nam Joong Jeon, Jun Hong NohWoon Seok YangYoung Chan KimSeungchan RyuJangwon Seo & Sang Il Seok, Nature 2015





Light-Induced Dipole Moment Change in Organometal Halide Perovskites

3 01 2015

The polarizability of organic-metal-halide perovskites has become a topic of great interest. In june 2014 we reported (Photoinduced Giant Dielectric Constant in Lead Halide Perovskite Solar Cells, Emilio J. Juarez-Perez et al. ) that the dielectric constant of CH3NH3PbI3 becomes enormous at very low frequencies, and the effect becomes strongly amplified when the perovskite is illuminated. This phenomenon is intriguing and very important as it indicates that there are strong changes of ionic-electronic structure when the perovskite is photoexcited. However, in general large dielectric constant can also be produced by macrosocopic polarization at interfaces. Therefore it is very important to combine capacitance measurements with determination of microscopic dipolar moments in different conditions. The paper by Ni Zhao et al presents a good contribution to this discussion by determination of photoinduced dipole moments by electroabsorption technique.

Composition-Dependent Light-Induced Dipole Moment Change in Organometal Halide Perovskites

Xiaojing Wu , Hui Yu , Linkai Li , Feng Wang ,Haihua Xu , and Ni Zhao
J. Phys. Chem. C, 2015
DOI: 10.1021/jp511314a
In this work we investigate the compositional dependence of electric dipole moment in AMX3(A: organic; M: metal; X: halogen) perovskite structures using modulation electroabsorption (EA) spectroscopy. By sampling various device structures we show that the second harmonic EA spectra reflect the intrinsic dipolar property of perovskite films in a layered configuration. A quantitative analysis of the EA spectra of CH3NH3PbI3, NH2CHNH2PbI3 and CH3NH3Sn0.4Pb0.6I3 is provided to compare the impact of the organic and metal cations on the photoinduced response of dipole moment. Based on the EA results, we propose that the A and M cations could both largely affect the dielectric and dipolar properties of the perovskite materials, but through different mechanisms, such as ionic polarization, rotation of molecular dipoles and charge migration. These processes occur at different time scales and thus result in a frequency-dependent dipole response.




5 years of JPCL

2 01 2015

The Journal of Physical Chemistry Letters (JPCL) is now 5 years old. Within this short period,JPCL has emerged as one of the eminent journals in the discipline by disseminating significant scientific advances in physical chemistry, chemical physics, and materials science.

Read the editorial by Prashant Kamat et al.