A Breakthrough Efficiency of 19.9% Obtained in Inverted Perovskite Solar Cells by Using an Efficient Trap State Passivator Cu(thiourea)I

Meng

2017

374

265

Organic‐inorganic halide perovskite materials have become a shining star in the photovoltaic field due to their unique properties, such as high absorption coefficient, optimal bandgap, and high defect tolerance, which also lead to the breathtaking increase in power conversion efficiency from 3.8% to over 22% in just seven years. Although the highest efficiency was obtained from the TiO2 mesoporous structure, there are increasing studies focusing on the planar structure device due to its processibility for large‐scale production. In particular, the planar p‐i‐n structure has attracted increasing attention on account of its tremendous advantages in, among other things, eliminating hysteresis alongside a competitive certified efficiency of over 20%. Crucial for the device performance enhancement has been the interface engineering for the past few years, especially for such planar p‐i‐n devices. The interface engineering aims to optimize device properties, such as charge transfer, defect passivation, band alignment, etc. Herein, recent progress on the interface engineering of planar p‐i‐n structure devices is reviewed. This review is mainly focused on the interface design between each layer in p‐i‐n structure devices, as well as grain boundaries, which are the interfaces between polycrystalline perovskite domains. Promising research directions are also suggested for further improvements.

Section: Grain Boundaries In the Perovskite Active Layermentioning

confidence: 99%

Section: Wwwadvenergymatdementioning

confidence: 99%

Interface Engineering for Highly Efficient and Stable Planar p‐i‐n Perovskite Solar Cells

Meng

2017

374

265

“…[1][2][3][4][5][6][7][8] Although the highest certified PCE of PSCs is comparable to that of commercialized silicon photovoltaic devices, the poor long-term stability of PSCs is an unavoidable hurdle to widespread application. The power conversion efficiency (PCE) of PSCs has exhibited an unprecedented rise from the initial 3.8% to over 22% in the past few years.…”

mentioning

confidence: 99%

Morphology Controlling of All‐Inorganic Perovskite at Low Temperature for Efficient Rigid and Flexible Solar Cells

Rao

et al. 2018

Self Cite

127

109

organic components with inorganic cations such as cesium (Cs + ) and rubidium (Rb + ) ions can effectively improve the thermal stability. Recently, all-inorganic cesium lead halide perovskites (CsPbX 3 , X = I, Br, Cl, or mixed halides), which have higher melting points (in excess of 460 °C), [10] have been investigated as thermal stable photoabsorption materials. The CsPbI 2 Br perovskites, which possess a reasonable bandgap of 1.9 eV and considerable phase stability, were emphasized as the main research subject in previous work. [24][25][26][27][28][29][30] To improve the performance of CsPbX 3 -based PSCs, a series of work on composition [18,19] and fabrication [20][21][22][23][24] engineerings have been intensely carried out. Unfortunately, the CsPbX 3 perovskites generally require high-temperature annealing (>250 °C) to form black photovoltaic-active cubic phase, [27][28][29][30] which is energy-consuming and undesirable for multijunction tandem and flexible solar cells. Up to now, it is still challenging to obtain uniform and void-free CsPbX 3 perovskite films via low-temperature solution-processed methods, let alone room temperature (RT) based technologies.In this work, we demonstrate that coordinated solvent dimethylsulphoxide (DMSO) can effectively induce the RT formation of photovoltaic-active CsPbX 3 perovskites, and a simple RT solvent (DMSO) annealing (RTSA) treatment can controllably remove the high boiling point DMSO and result in highly uniform and void-free CsPbX 3 perovskite films, as well as a postannealing treatment at the moderate temperature of 120 °C can further improve the perovskite grain size and crystallinity. These results provide an approach to prepare high quality allinorganic CsPbX 3 perovskite films at RT or a relatively low temperature (<120 °C). Consequently, efficient inverted CsPbI 2 Brbased PSCs were achieved on both glass and flexible substrates.As previously reported, [27] the CsPbI 2 Br perovskite precursor solution in N,N-dimethylformamide (DMF) suffers from a low concentration (≈0.43 m) due to the solubility limitation of bromide. While for the perovskite precursor solution with DMSO as solvent, the stronger coordination interaction between DMSO and the perovskite precursor enables the concentration exceeding 2 m ( Figure S1, Supporting Information), resulting in thicker perovskite films with sufficient light absorption ( Figure S2, Supporting Information). Furthermore, All-inorganic cesium lead halide (CsPbX 3 ) perovskites have emerged as promising photovoltaic materials owing to their superior thermal stability compared to traditional organic-inorganic hybrid counterparts. However, the CsPbX 3 perovskites generally need to be prepared at high-temperature, which restricts their application in multilayer or flexible solar cells. Herein, the formation of CsPbX 3 perovskites at room-temperature (RT) induced by dimethylsulphoxide (DMSO) coordination is reported. It is further found that a RT solvent (DMSO) annealing (RTSA) treatment is valid to control the perovskite cryst...

“…The CuI@TiO 2 devices showed trap densities of 5.76 × 10 15 , 5.49 × 10 15 , and 3.45 × 10 15 cm −3 , and the TiO 2 device showed a trap density of 1.52 × 10 16 cm −3 . [32] Since the recombination rate (hundreds nanosecond scale) is much slower than the extraction rate (tenths nanosecond scale), [43] even if a part of the generated holes moves to CuI, positive CuI can pull the electron to the interface between TiO 2 and perovskite layer with very low recombination. Moreover, the electron mobility of bare TiO 2 and CuI@TiO 2 device is calculated by the SCLC method in Figure 4d.…”

mentioning

confidence: 99%

p‐Type CuI Islands on TiO₂ Electron Transport Layer for a Highly Efficient Planar‐Perovskite Solar Cell with Negligible Hysteresis

Byranvand

Kim

Song

et al. 2017

130

Perovskite solar cells (PSCs) have attracted much attention owing to their high power conversion efficiencies (PCEs) and relatively low fabrication costs compared with conventional silicon-based solar cells. [1,2] In a planar n-i-p-type PSC, a perovskite layer is sandwiched between a fluorine-doped tin oxide (FTO) glass substrate with an electron transport layer (ETL) and a hole transport layer (HTL) with metal electrode, respectively. The ETL plays an important role in electron extraction and hole blocking. A compact TiO 2 layer is widely used [3] as the ETL in PSCs owing to its excellent optical transmittance and superior chemical stability at high temperatures in air, although various ETL materials including metallic salts, [4] transition metal oxides, [5,6] or organic materials [7,8] have been reported. In addition, the TiO 2 compact layer can be easily prepared from its precursor solution via a sol-gel process. By employing such Compact TiO 2 is widely used as an electron transport material in planarperov skite solar cells. However, TiO 2 -based planar-perovskite solar cells exhibit low efficiencies due to intrinsic problems such as the unsuitable conduction band energy and low electron extraction ability of TiO 2 . Herein, the planar TiO 2 electron transport layer (ETL) of perovskite solar cells is modified with ionic salt CuI via a simple one-step spin-coating process. The p-type nature of the CuI islands on the TiO 2 surface leads to modification of the TiO 2 band alignment, resulting in barrier-free contacts and increased open-circuit voltage. It is found that the polarity of the CuI-modified TiO 2 surface can pull electrons to the interface between the perovskite and the TiO 2 , which improves electron extraction and reduces nonradiative recombination. The CuI solution concentration is varied to control the electron extraction of the modified TiO 2 ETL, and the optimized device shows a high efficiency of 19.0%. In addition, the optimized device shows negligible hysteresis, which is believed to be due to the removal of trap sites and effective electron extraction by CuI-modified TiO 2 . These results demonstrate the hitherto unknown effect of p-type ionic salts on electron transport material.