Enhancing the grain size of organic halide perovskites by sulfonate-carbon nanotube incorporation in high performance perovskite solar cells

Son

Advanced Energy Materials

et al. 2020

Although it has been reported that grain boundaries have not to adversely affect solar cell characteristics in CIGS and halide perovskite solar cell, nevertheless, an effective strategy for efficient carrier management in a CZTS layer is to make the grain size not too small. Generally, grain boundary control is a key concern for polycrystalline thin-film solar cells. [5][6][7][8][9][10][11] A light absorber consisting of small grains can degrade the device performance due to the vertical current flow through the multiple grain boundaries. Current and voltage loss can derive from nonradiative recombination of electrons and holes and scattering at grain boundaries. In fact, CZTSSe solar cells with efficiencies above 12% have a grain size over micrometer scale. [12][13][14][15] Generally, as the annealing temperature and time increase, the grain size increases. The efficiency is expected to decrease when the temperature and annealing time are increased due to the decomposition of CZTSSe by Mo [16,17] and the increase in the MoSSe thickness [16] and Sn loss. [18] Therefore, a liquid-assisted grain growth (LGG) method could be a good method for increasing the grain size at low temperatures over a short time while suppressing the Sn loss, growth of MoSSe and CZTSSe decomposition by Mo. The liquid phase that exists during grain growth plays a role as a diffusion path necessary for material movement such that grain growth more effectively occurs. [19] To date, liquid-assisted grain growth (LGG) has been achieved by controlling the partial pressure of chalcogen vapor to form a liquid phase at the grain boundary of CZTSSe nanoparticles. [7,20] Liquid Cu-Se causes LGG in a Cu-rich composition, and the vapor-liquidsolid (VLS) model has been adopted; [21,22] similarly, LGG might occur in the GeSe 2 -Se system. [23][24][25] Additionally, LGG can occur through the eutectic reaction of the Na-Se system; [24][25][26][27] a similar eutectic reaction can occur in other alkali-chalcogen (AX) systems (AX; A = Li, Na, K, Cs, Rb; X = Se, Te). [28] In addition, LGG might occur due to liquid phase generation upon the addition of dopants, such as Sb 2 S 3 , [29] CuSbS 2 , [29] and NaSb 5 S 8 ; [29] similar eutectic reactions can occur in other similar systems (ASb 5 X 8 ; A = Li, Na, K, and Cs, Rb; X = S, Se, and Te). [28] Additionally, LGG can occur with Ag substitution due to the Ag-related alloy. [30] The similarity is the liquid phase formation due to the existence of the eutectic reaction point (Solid A + Solid B → Liquid) or the liquidus line at the process Herein, a liquid-assisted grain growth (LGG) mechanism for a vacuumprocessed Cu 2 ZnSn(S 1−x Se x ) 4 (CZTSSe) absorber that is enabled by the presence of a liquid phase containing predominantly Cu, Sn, and Se (L-CTSe) is suggested to explain the large grain size of up to ≈6 µm obtained at low temperatures, such as 480 °C. In this system, LGG plays a key role in achieving a large grain CZTSSe absorber, but the residual L-CTSe, a key factor in LGG, deteriorates the device performa...

Section: Introductionmentioning

confidence: 99%

Effect of Cu–Sn–Se Liquid Phase on Grain Growth and Efficiency of CZTSSe Solar Cells

Son

Advanced Energy Materials

et al. 2020

ECS J. Solid State Sci. Technol.

“…130 For example, fullerene derivatives, such as PCBM, were used as hole transport layers and integrative component to reduce hysteresis and charge recombination. [131][132][133][134] Furthermore, SWCNTs and MWCNTs were used as dopants for HTMs, such as Spiro-MeOTAD, 135,136 as integrative component into the perovskite layer, 137,138 and as hole extraction layer. 139,140 As such, charge recombination losses were reduced and hole collection efficiencies were increased.…”

Section: Discussionmentioning

confidence: 99%

Review—Single-Walled Carbon Nanohorn-Based Dye-Sensitized Solar Cells

Lodermeyer

Costa

Guldi

2017

Efforts in the broad field of dye-sensitized solar cells (DSSC) are governed by four key challenges: i) the development of photoelectrodes with high charge injection yields and charge collection efficiencies, ii) the development of low-cost buffer layers, which effectively reduce the back reaction of electrons from the transparent conductive oxide (TCO) to the electrolyte, iii) the design of platinum-free counter electrodes (CE), which feature good electrolyte regeneration yields, and iv) the implementation of (quasi) solid-state and iodine-free electrolytes featuring excellent ionic diffusion and conductivity.

“…Interestingly, a broad range of physical and chemical characteristics of CNT, possibly endowed by chemical modification and heteroatom doping, could provide open opportunities for the perovskite‐based hybrid structures and interfacial engineering 13b,14. Recently, CNT has been utilized as reinforcing components in the perovskite layers for optoelectronic applications, particularly motivated from their high charge carrier mobility . Nonetheless, the strong tendency for aggregation and intrinsic chemical inertness of pristine CNT makes it challenging to achieve a desired synergistic integration 15d,16.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, CNT has been utilized as reinforcing components in the perovskite layers for optoelectronic applications, particularly motivated from their high charge carrier mobility . Nonetheless, the strong tendency for aggregation and intrinsic chemical inertness of pristine CNT makes it challenging to achieve a desired synergistic integration 15d,16. Moreover, potential interaction mechanism between perovskite crystal structure and graphene plane is still unclear, which is crucial for the desirable hybrid structures.…”

Section: Introductionmentioning

confidence: 99%

Nitrogen‐Dopant‐Induced Organic–Inorganic Hybrid Perovskite Crystal Growth on Carbon Nanotubes

Lee

Yang

et al. 2019

Adv Funct Materials

Interfacial engineering of organic-inorganic halide perovskites in conjunction with different functional materials is anticipated to offer novel heterojunction structures with unique functionalities. Unfortunately, complex material compositions and structures of the organic-inorganic hybrid materials make it difficult to tailor a desirable intermolecular interaction at the interface. Spontaneous and highly specific nucleation of perovskite crystals, that is, methylammonium lead iodide perovskite (CH 3 NH 3 PbI 3 , MAPbI 3 ) at nitrogendoped carbon nanotube (NCNT) surfaces for the self-assembly of MAPbI 3 / NCNT hybrids is reported. It is demonstrated that the lone-pair electrons of pyridinic nitrogen-dopant sites at NCNTs mediate specific interactions with the cationic component in the perovskite structure and serve as the nucleation sites via coordinate bonding formation, as supported by X-ray photoelectron spectroscopy and density functional theory calculation. The potential suitability of MAPbI 3 /NCNT hybrids is presented for highly sensitive and selective NO 2 sensing layer. This work suggests a reliable self-assembly route to the molecular level hybridization of organic-inorganic halide perovskites by employing the substitutional dopant sites at graphene-based nanomaterials.