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Advancements in Perovskite Solar Cells: Photophysics behind the Photovoltaics
Tze Chien Sum 1* and Nripan Mathews 2,3,4*
1
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang
Technological University, 21 Nanyang Link, Singapore 637371.
2
School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue,
负担英文Singapore 639798.
3
Energy Rearch Institute @NTU (ERI@N), Rearch Techno Plaza, X-Frontier Block, Level 5, 50
Nanyang Drive, Singapore 637553.
4
Singapore-Berkeley Rearch Initiative for Sustainable Energy, 1 Create Way, Singapore 138602,
Singapore.
*Correspondence to: Tzechien@ntu.edu.sg ; Nripan@ntu.edu.sg
Page 1 of 34Energy & Environmental Science
E n e r g y &E n v i r o n m e n t a l S c i e n c e A c c e p t e d M a n u s c r i p t
P u b l i s h e d o n 02 M a y 2014. D o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 28/05/2014 11:37:31.
fight的过去式View Article Online
DOI: 10.1039/C4EE00673A
Abstract
receive的用法
Solution-procesd organic-inorganic perovskite solar cells are hailed as the recent major breakthrough in low-cost photovoltaics. Power conversion efficiencies approaching that of
crystalline Si solar cells (exceeding 15%) have been reported. Remarkably, such phenomenal performances were achieved in a matter of 5 years – up from ~3.8% back in 2009. Since then, the field has expanded exponentially. In this perspective, we review the basic working mechanisms of perovskite solar cells in relation to their intrinsic properties and fundamental photophysics. The current state-of-the-art and the open questions in this maturing field are also highlighted.
Keywords: Perovskite Solar Cells, Organic-inorganic lead halides; device performance; charge dynamics and photophysics
Page 2 of 34
hey jude 歌词Energy & Environmental Science E n e r g y &E n v i r o n m e n t a l S c i e n c e A c c e p t e d M a n u s c r i p t
P u b l i s h e d o n 02 M a y 2014. D o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 28/05/2014 11:37:31.
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theDOI: 10.1039/C4EE00673A
1. Introduction
Solar power is the world's most abundant energy resource. A year's worth of sunlight contains 1.5
× 1018 kWh of energy. By comparison, the known rerves of oil, coal, and gas are 1.75 ×1015 kWh, 1.4
×1015kWh, and 5:5 ×1015 kWh, respectively. Thus, a year’s worth of sunlight provides more than a hundred times the energy of the world's entire known fossil fuel rerves. Harnessing solar power would yield a never-ending energy supply.1 The difficulty has always been converting solar energy in an efficient and cost-effective way. Photovoltaic cells are the most promising avenue, directly converting the photons to electricity. For photovoltaic energy to become competitive with fossil fuels and capture a significant share of the electricity market, it is necessary to reduce the total cost of solar energy. This can be achieved by either reducing the cost of photovoltaic cells or by increasing their power conversion efficiency.
The photovoltaic market is currently dominated by crystalline Si solar cells with efficiencies
clo to 20%. Alternative “third generation” technologies such as organic photovoltaics (OPVs), dye nsitized solar cells (DSCs) and quantum dot solar cells (QDSCs) which are fabricated through solution bad process such as blade coating, screen printing and spraying, promi low cost solar power while allowing the utilization of unconventional substrates. Although the utilization of low temperature process reduces the energetic costs and the energy payback time, the power conversion efficiencies (PCEs) of the solar cells still lag significantly behind conventional solar cells. The levelized cost of energy (LCOE) which allows for the comparison of various electricity generation sources, depends critically on the efficiency of the solar cells produced.2 A more efficient module yields more power per unit area. A significant fraction of a solar cell's cost scales proportional to the installation area, including the cost of the glass, inverter costs and installation costs, among others. A more efficient solar cell allows for a reduction in all the costs associated with installation, while requiring much lower numbers of solar panels to be installed. Thus power conversion efficiency is a primary driver of cost for solar cells.
Organic-inorganic halide perovskite solar cells has been the most significant development in the
field of photovoltaics in the prent decade and is the best bet at satisfying the need for high efficiencies while allowing for low cost solution bad manufacturing. Since the first reports of stable solid state solar cells bad on CH 3NH 3PbI 3 perovskite in mid-2012, the PCEs of the solar cells have already exceeded 15%, leapfrogging every other solution-procesd solar cell technology. The wide range of efficient perovskite solar cell device architectures demonstrated point towards a remarkable miconducting material with excellent electrical and optical properties. Early pioneering work 3, 4 in the area of organic-inorganic halides has clearly shown that this class of materials can behave as low dimensional electronic
Page 3 of 34Energy & Environmental Science
E n e r g y &E n v i r o n m e n t a l S c i e n c e A c c e p t e d M a n u s c r i p t
P u b l i s h e d o n 02 M a y 2014. D o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 28/05/2014 11:37:31.
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财务统计DOI: 10.1039/C4EE00673A
雅思预测
systems with tunable properties, allowing for the development of newer perovskite solar materials in
addition to CH 3NH 3PbI 3.
This review focus on the recent developments (i.e., up to Feb 2014) in perovskite solar cells as
well as their photophysical properties and charge dynamics. We first review the intrinsic physical and electronic properties of this class of organic-inorganic perovskites, followed by its progress as a photovoltaic material. The review then examines the recent photophysical studies on unraveling the charge dynamics and transport mechanisms in both perovskite thin films as well as in perovskite solar cells. Due to the rapid pace of rearch in this area, this review does not aim to be comprehensive but will highlight key work and findings. Lastly, we conclude the review with the open questions facing the class of solar cells and future directions of rearch.
2. Intrinsic Properties of Organic-Inorganic Perovskites (a)
Physical Structure
Perovskites is a common nomenclature for compounds with the generic chemical formula of
AMX 3. In the cubic unit cell, the A-cation resides at the eight corners of the cube, while the M-cation is located at the body center that is surrounded by 6 X-anions (located at the face centers) in an octahedral [MX 6]4- cluster. Typical inorganic perovskites include CaTiO 3 and SrTiO 3. Due to the interplay of the charge, spin and structural properties, this family of materials is known to exhibit a plethora of novel and exciting phenomena such as superconductivity, magnetoresistance, ferroelectricity, magnetoelectricity, anti-ferromagnetism, anti-ferroelectricity etc .5 In the class of compounds being discusd here, the A cations are organic (typically CH 3NH 3+,C 2H 5NH 3+, HC(NH 2)2+), the metal cations (M) are typically divalent metal ions such as Pb 2+, Sn 2+, Eu 2+, Cu 2+ etc, while the X anions are halides (Cl -, Br -, I -). CH 3NH 3PbI 3 belongs to a large family of organic-inorganic perovskites where the [PbI 6]4- octahedral can form 3-D, two-dimensional (2-D), one-dimensional (1-D) or zero-dimensional (0-D) networks, posssing the same unit structure – Figure 1. The abnce of any inhomogenous broadening (arising from size distribution of the samples) in the 3-D and their low-dimensional counterparts makes the compounds ideal for investigating quantum confinement effects in miconductor mesoscopic structures. Pioneering work in this class of compounds began as early as 1989 where the focus was on the effects of dimensionality on the excitonic, optical and electronic properties.4, 6, 7 The optoelectronic properties of layered organic-inorganic perovskites were also extensively studied becau of the novel properti
es exhibited by the crystals which include: high mobilities for thin-film transistors 8, 9; strong excitonic
clothes是什么意思Page 4 of 34
Energy & Environmental Science E n e r g y &E n v i r o n m e n t a l S c i e n c e A c c e p t e d M a n u s c r i p t
布兰妮最经典的歌
P u b l i s h e d o n 02 M a y 2014. D o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 28/05/2014 11:37:31.
viewportView Article Online
DOI: 10.1039/C4EE00673A
properties for light emitting diodes 10, 11; large nonlinearities with ultrafast respon 12, 13; and even
polariton emission in 2D perovskite-bad microcavities.14-18
In CH 3NH 3PbI 3, each [PbI 6]4- octahedron is connected with six neighbours at the iodide – forming
a 3-D network. The countercation (CH 3NH 3+) is located at the void of the network. For the 2-D ca 19 (e.g., (CH 3NH 3)2PbI 4, each [PbI 6]4- octahedron is connected with four neighbours at the halide – forming a 2-D network layer that is sandwiched between two CH 3NH 3+ layers (also not shown in figure). A multiple quantum well structure results with the stacking of the sandwiched layers via van der Waals interaction – with the 2-D [PbI 6]4- functioning as the quantum well and the CH 3NH 3+ layer as the barrier. For the 1-D ca 20 (e.g., (NH 2C(I) = NH 2)3PbI 5), each octahedron is connected at two opposite corners with its neighbour – forming parate infinite chains. Lastly, the quantum dot (0-D) analogue manifests as (CH 3NH 3)4PbI 6.2H 2O, where each [PbI 6]4- complex is neutralized by four CH 3NH 3+ ions to form a molecule. A quantum dot array results when the molecules are isolated by H 2O molecules to form a molecular crystal.
Figure 1: Crystal Structures of (a) CH 3NH 3PbI 3,21 (b) (CH 3NH 3)2PbI 4,19 (c) (C 10H 21NH 3)2PbI 4,20 and (d) (CH 3NH 3)4PbI 6.2H 2O,22 corresponding to 3D, 2D, 1D and 0D networks. The blue polyhedra reprent the MX 6 (M = Pb, Sn and Cu; X = I and Br) octahedra with the halogens reprented by orange spheres – the building block of the compounds. The blue, green and red spheres are the N, C and O respectively (the H ions were removed for clarity). The ID network extends into the plane of the document.
Page 5 of 34Energy & Environmental Science
E n e r g y &E n v i r o n m e n t a l S c i e n c e A c c e p t e d M a n u s c r i p t
P u b l i s h e d o n 02 M a y 2014. D o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 28/05/2014 11:37:31.
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DOI: 10.1039/C4EE00673A
