JIALINGBO

A diffusion-regulated ternary structure containing two narrow-bandgap non-fullerene acceptors enhances the absorption in the near-infrared region. By integration with wide-bandgap perovskite front subcells, a power conversion efficiency of 24.5% is achieved in perovskite/organic tandem solar cells.

Abstract

The compatibility of perovskite and organic photovoltaic materials in solution processing provides a significant advantage in the fabrication of high-efficiency perovskite/organic tandem solar cells. However, additional recombination losses can occur during exciton dissociation in organic materials, leading to energy losses in the near-infrared region of tandem devices. Consequently, a ternary organic rear subcell is designed containing two narrow-bandgap non-fullerene acceptors to enhance the absorption of near-infrared light. Simultaneously, a unique diffusion-controlled growth technique is adopted to optimize the morphology of the ternary active layer, thereby improving exciton dissociation efficiency. This innovation not only broadens the absorption range of near-infrared light but also facilitates the generation and effective dissociation of excitons. Owing to these technological improvements, the power conversion efficiency (PCE) of organic solar cells increased to 19.2%. Furthermore, a wide-bandgap perovskite front subcell is integrated with a narrow-bandgap organic rear subcell to develop a perovskite/organic tandem solar cell. Owing to the reduction in near-infrared energy loss, the PCE of this tandem device significantly improved, reaching 24.5%.

Publication date: 1 December 2024

Source: Nano Energy, Volume 131, Part A

Author(s): Mohammad Reza Golobostanfard, Mostafa Othman, Deniz Turkay, Kerem Artuk, Xin Yu Chin, Mounir Driss Mensi, Daniel Anthony Jacobs, Quentin Jeangros, Christian Michael Wolff, Aïcha Hessler-Wyser, Christophe Ballif

Publication date: 1 December 2024

Source: Nano Energy, Volume 131, Part B

Author(s): Ruowei He, Weichun Pan, Pengxu Chen, Qingshui Zheng, Anling Tong, Jiexi Pan, Zhihang Jin, Weihai Sun, Yunlong Li, Jihuai Wu

1D porous channels and high crystalline orientation of imidazole-linked porphyrin-based covalent organic framework (PyPor-COF) facilitate the crystallization and defect elimination of the perovskite film. The recombination of photogenerated carriers is thus reduced and the perovskite solar cells exhibit excellent efficiency and high stability.

Abstract

The low crystallinity of the perovskite layers and many defects at grain boundaries within the bulk phase and at interfaces are considered huge barriers to the attainment of high performance and stability in perovskite solar cells (PSCs). Herein, a robust photoelectric imidazole-linked porphyrin-based covalent organic framework (PyPor-COF) is introduced to precisely control the perovskite crystallization process and effectively passivate defects at grain boundaries through a sequential deposition method. The 1D porous channels, abundant active sites, and high crystallization orientation of PyPor-COF offer advantages for regulating the crystallization of PbI₂ and eliminating defects. Moreover, the intrinsic electronic characteristics of PyPor-COF endow a more closely matched energy level arrangement within the perovskite layer, which promotes charge transport and thereby suppresses the recombination of photogenerated carriers. The champion PSCs containing PyPor-COF achieved power conversion efficiencies of 24.10% (0.09 cm²) and 20.81% (1.0 cm²), respectively. The unpackaged optimized device is able to maintain its initial efficiency of 80.39% even after being exposed to air for 2000 h. The device also exhibits excellent heating stability and light stability. This work gives a new impetus to the development of highly efficient and stable PSCs via employing COFs.

Publication date: 1 December 2024

Source: Nano Energy, Volume 131, Part A

Author(s): EQ Han, Jung-Ho Yun, Inhee Maeng, Tengfei Qiu, Yurou Zhang, Eunyoung Choi, Su-Min Lee, Peng Chen, Mengmeng Hao, Yang Yang, Hongxia Wang, Bo Wei Zhang, Jae Sung Yun, Jan Seidel, Miaoqiang Lyu, Lianzhou Wang

2D perovskite passivation is a mainstream strategy to address the perovskite/C₆₀ interface problem. Organic molecules in 2D perovskites come into direct contact with C₆₀, forming π–π stacking at the perovskite/C₆₀ interface to enhance interaction. This improves the quality of the perovskite/C₆₀ interface and ultimately achieves the goal of enhancing device performance.

Abstract

Interface passivation is a key method for improving the efficiency of perovskite solar cells, and 2D/3D perovskite heterojunction is the mainstream passivation strategy. However, the passivation layer also produces a new interface between 2D perovskite and fullerene (C₆₀), and the properties of this interface have received little attention before. Here, the underlying properties of the 2D perovskite/C₆₀ interface by taking the 2D TEA₂PbX₄ (TEA = C₆H₁₀NS; X = I, Br, Cl) passivator as an example are systematically expounded. It is found that the 2D perovskite preferentially exhibits (002) orientation with the outermost surface featuring an oriented arrangement of TEACl, where the thiophene groups face outward. The outward thiophene groups further form a strong π–π stacking system with C₆₀ molecule, strengthening the interaction force with C₆₀ and facilitating the creation of a superior interface. Based on the vacuum-assisted blade coating, wide-bandgap (WBG, 1.77 eV) perovskite solar cells achieved impressive records of 19.28% (0.09 cm²) and 18.08% (1.0 cm²) inefficiency, respectively. This research not only provides a new understanding of interface processing for future perovskite solar cells but also lays a solid foundation for realizing efficient large-area devices.

A molecule-triggered strain regulation and interface passivation strategy via the [2 + 2] cycloaddition reaction of 6-bromocoumarin-3-carboxylic acid ethyl ester, which absorbs harmful UV light, is proposed to achieve strain regulation and reduce interface defects. The perovskite solar cell exhibits a champion efficiency of up to 26.32% (certified efficiency: 26.08%) with excellent long-term stability.

This work demonstrates that the capability of hole molecules to strengthen the interface bonding and interactions between molecules and interfaces is crucial to maximally passivate defects, affording robust interface, inhibition of ion migration, and photostable perovskite solar cells. Consequently, the newly developed mDPA-SFX enables cells with a PCE of 24.8 %, and an excellent T ₈₀ lifetime of 2,238 h at maximum power point tracking.

Abstract

Poor operational stability is a crucial factor limiting the further application of perovskite solar cells (PSCs). Organic semiconductor layers can be a powerful means for reinforcing interfaces and inhibiting ion migration. Herein, two hole-transporting molecules, pDPA-SFX and mDPA-SFX, are synthesized with tuned substituent connection sites. The meta-substituted mDPA-SFX results in a larger dipole moment, more ordered packing, and better charge mobility than pDPA-SFX, accompanying with strong interface bonding on perovskite surfaces and suppressed ion motion as well. Importantly, mDPA-SFX-based PSCs exhibit an efficiency that has significantly increased from 22.5 % to 24.8 % and a module-based efficiency of 19.26 % with an active area of 12.95 cm². The corresponding cell retain 94.8 % of its initial efficiency at maximum power point tracking (MPPT) after 1,000 h (T ₉₅=1,000 h). The MPPT T ₈₀ lifetime is as long as 2,238 h. This work illustrates that a small degree of structural variation in organic compounds leaves considerable room for developing new HTMs for light stable PSCs.

The molecular synergistic effect enabled by piperazine-1-carboxamide hydrochloride and 1,3-propane-diammonium iodide facilitates excellent energy level alignment and reduces non-radiative recombination losses and light-induced phase segregation. The target perovskite/perovskite/silicon triple-junction tandem solar cell obtains an open-circuit voltage of 3.07 V and a champion power conversion efficiency of 25.2% (for a 1.035 cm² aperture area).

Abstract

Perovskite/perovskite/silicon triple-junction tandem solar cells (TSCs) hold promise for high power conversion efficiencies (PCE). However, the efficiency is still relatively low due to the non-radiative recombination losses in wide-bandgap top cells. These losses, attributed to the interface defect states and energy level mismatches, present considerable challenges to realizing high-performance and stable TSCs. Here, the molecular synergistic effect (MSE) is exploited to passivate interface in 1.95 eV top cells. Piperazine-1-carboxamide hydrochloride (PCACl) is combined, which possesses strong dipole moments and passivating functional groups that can bind with two neighboring uncoordinated lead ions and form hydrogen bonds with halide atoms at perovskite surface, with 1,3-propane-diammonium iodide, which can reduce interface recombination through field-effect passivation. The MSE enabled by PCACl and PDAI₂ facilitates excellent energy level alignment and reduces non-radiative recombination losses and light-induced phase segregation. Finally, the target perovskite/perovskite/silicon triple-junction TSC obtains an open-circuit voltage of 3.07 V and a champion PCE of 25.2% (for a 1.035 cm² aperture area).

Nature Communications, Published online: 20 August 2024; doi:10.1038/s41467-024-51550-z

The defects at the perovskite/carrier transport layer interface pose significant challenges to the performance of perovskite solar cells. Here, the authors introduce a dual host-guest complexation strategy with Cs-crown-ether and ammonium salt, achieving a high PCE of 25.9% with superior stability.

Nature Energy, Published online: 07 August 2024; doi:10.1038/s41560-024-01600-z

Perovskite solar cells degrade when subjected to reverse bias. Jiang et al. show that relatively thick hole transport layers and metal back contacts with improved electrochemical stability afford better tolerance to reverse bias.

A series of tetrapodal hole-collecting monolayer materials based on a saddle-like cyclooctatetraene core were developed. These molecules were found to form monolayers on transparent electrode substrates, with some phosphonic acid anchoring groups pointing upward, resulting in hydrophilic surfaces. The perovskite solar cell devices using these hole-collecting monolayers exhibit high power conversion efficiencies of up to 21.7 % and good operational stability.

Abstract

Hole-collecting monolayers have greatly advanced the development of positive-intrinsic-negative perovskite solar cells (p-i-n PSCs). To date, however, most of the anchoring groups in the reported monolayer materials are designed to bind to the transparent conductive oxide (TCO) surface, resulting in less availability for other functions such as tuning the wettability of the monolayer surface. In this work, we developed two anchorable molecules, 4PATTI-C3 and 4PATTI-C4, by employing a saddle-like indole-fused cyclooctatetraene as a π-core with four phosphonic acid anchoring groups linked through propyl or butyl chains. Both molecules form monolayers on TCO substrates. Thanks to the saddle shape of a cyclooctatetraene skeleton, two of the four phosphonic acid anchoring groups were found to point upward, resulting in hydrophilic surfaces. Compared to the devices using 4PATTI-C4 as the hole-collecting monolayer, 4PATTI-C3-based devices exhibit a faster hole-collection process, leading to higher power conversion efficiencies of up to 21.7 % and 21.4 % for a mini-cell (0.1 cm²) and a mini-module (1.62 cm²), respectively, together with good operational stability. This work represents how structural modification of multipodal molecules could substantially modulate the functions of the hole-collecting monolayers after being adsorbed onto TCO substrates.

Two multifunctional additives of AQS : FPMA and AQS : FPEA are developed to suppress the voltage loss of inverted inorganic perovskite solar cells of 1.78 eV and construct highly efficient and durable inverted inorganic perovskite/organic tandem solar cells. The formation of AQS-involved intermediate phase regulate the crystalliztaion rate resulting in lower defects of inorganic perovskites. Moreover, the benchmark of T ₉₀ lifetime of perovskite/organic tandem solar cells under MPPT can be promoted to 1000 h, which will facilitate the real-world deployment.

Abstract

Inverted perovskite/organic tandem solar cells (P/O TSCs) suffer from poor long-term device stability due to halide segregation in organic–inorganic hybrid wide-band gap (WBG) perovskites, which hinders their practical deployment. Therefore, developing all-inorganic WBG perovskites for incorporation into P/O TSCs is a promising strategy because of their superior stability under continuous illumination. However, these inorganic WBG perovskites also face some critical issues, including rapid crystallization, phase instability, and large energy loss, etc. To tackle these issues, two multifunctional additives based on 9,10-anthraquinone-2-sulfonic acid (AQS) are developed to regulate the perovskite crystallization by mediating the intermediate phases and suppress the halide segregation through the redox-shuttle effect. By coupling with organic cations having the desirable functional groups and dipole moments, these additives can effectively passivate the defects and adjust the alignment of interface energy levels. Consequently, a record V _oc approaching 1.3 V with high power conversion efficiency (PCE) of 18.59 % could be achieved in a 1.78 eV band gap single-junction inverted all-inorganic PSC. More importantly, the P/O TSC derived from this cell demonstrates a T ₉₀ lifetime of 1000 h under continuous operation, presenting the most stable P/O TSCs reported so far.

A novel fullerene derivative (denoted as C₆₀-TMA) is synthesized and employed to modify the interface between perovskite and C₆₀. C₆₀-TMA can passivate the surface defects to suppress non-radiative recombination, form a cascade energy level to facilitate electron extraction, and induce secondary growth of perovskite, contributing to a champion PCE of 24.89 % for inverted PSCs with significantly improved thermal stability.

Abstract

The electron extraction from perovskite/C₆₀ interface plays a crucial role in influencing the photovoltaic performance of inverted perovskite solar cells (PSCs). Here, we develop a one-stone-for-three-birds strategy via employing a novel fullerene derivative bearing triple methyl acrylate groups (denoted as C₆₀-TMA) as a multifunctional interfacial layer to optimize electron extraction at the perovskite/C₆₀ interface. It is found that the C₆₀-TMA not only passivates surface defects of perovskite via coordination interactions between C=O groups and Pb²⁺ cations but also bridge electron transfer between perovskite and C₆₀. Moreover, it effectively induces the secondary grain growth of the perovskite film through strong bonding effect, and this phenomenon has never been observed in prior art reports on fullerene related studies. The combination of the above three upgrades enables improved perovskite film quality with increased grain size and enhanced crystallinity. With these advantages, C₆₀-TMA treated PSC devices exhibit a much higher power conversion efficiency (PCE) of 24.89 % than the control devices (23.66 %). Besides, C₆₀-TMA benefits improved thermal stability of PSC devices, retaining over 90 % of its initial efficiency after aging at 85 °C for 1200 h, primarily due to the reinforced interfacial interactions and improved perovskite film quality.

A novel fullerene-based hole transport material (FHTM) has been designed and synthesized, exhibiting high hole mobility through intramolecular electron transfer. Incorporating FHTM at the NiO_x/perovskite interface optimizes the energy level alignment and improves the quality of the perovskite layer. This integration results in an inverted perovskite solar cell with a champion efficiency of 25.58 % (certified:25.04 %) and enhanced stability.

Abstract

Designing an efficient modification molecule to mitigate non-radiative recombination at the NiO_x/perovskite interface and improve perovskite quality represents a challenging yet crucial endeavor for achieving high-performance inverted perovskite solar cells (PSCs). Herein, we synthesized a novel fullerene-based hole transport molecule, designated as FHTM, by integrating C₆₀ with 12 carbazole-based moieties, and applied it as a modification molecule at the NiO_x/perovskite interface. The in situ self-doping effect, triggered by electron transfer between carbazole-based moiety and C₆₀ within the FHTM molecule, along with the extended π conjugated moiety of carbazole groups, significantly enhances FHTM's hole mobility. Coupled with optimized energy level alignment and enhanced interface interactions, the FHTM significantly enhances hole extraction and transport in corresponding devices. Additionally, the introduced FHTM efficiently promotes homogeneous nucleation of perovskite, resulting in high-quality perovskite films. These combined improvements led to the FHTM-based PSCs yielding a champion efficiency of 25.58 % (Certified: 25.04 %), notably surpassing that of the control device (20.91 %). Furthermore, the unencapsulated device maintained 93 % of its initial efficiency after 1000 hours of maximum power point tracking under continuous one-sun illumination. This study highlights the potential of functionalized fullerenes as hole transport materials, opening up new avenues for their application in the field of PSCs.

Pseudo-halide anion formate has been widely employed in perovskite solar cells (PSCs) due to its passivation effect. This work unveils the distinguishable crystallization behavior and different passivation mechanisms by comparing various formate salts. Notably, sodium-based formate salt exhibited bi-directional behavior of cation and anion in the device, distinguishing it from other formate salts. The device with bi-directional behavior of cation and anion exhibited an enhanced power conversion efficiency (PCE) of over 25% and improved operational stability.

The (N,N,N′,N′-tetramethyl-1,4-butanediammonium (TMBD))²⁺ spacer, adopting alternating alignment, directs a near linear 1D bismuth bromide perovskite lattice structure with relaxed microstrain, enhanced electron coupling, and reduced electron–phonon interaction as well. These merits contribute to facilitated charge transport and inhibited ion migration. As a result, the (TMBD)BiBr₅ single crystal delivers superior photoconductivity performance.

Abstract

Bismuth halide hybrid perovskites have emerged as promising alternatives to their lead halide homologs because of high chemical stability, low toxicity, and structural diversity. However, their advancements in optoelectronic field are plagued with poor charge transport, due to considerable microstrain triggered by bulky spacer. Herein, the di-tertiary ammonium spacer (N,N,N′,N′-tetramethyl-1,4-butanediammonium, TMBD) is explored to direct stable 1D bismuth bromide lattice structure with relaxed microstrain. Compared to the primary pentamethylenediamine (PD)²⁺, the (TMBD)²⁺ adopting alternating alignment enables a unique H-bonds mode to distort the configuration of inorganic layers to form corner-sharing [BiBr₅] near-regular chains with narrower bandgap, lower exciton binding energy, and reduced carrier–lattice interactions, thereby facilitating charge-carrier transport. Moreover, the (TMBD)²⁺ spacers largely suppress ion migration in perovskite lattice, as substantiated by the experimental and theoretical investigations. Consequently, (TMBD)BiBr₅ single crystal photodetector delivers a 185-fold increase in current on/off ratio with respect to (PD)BiBr₅ under white light irradiation, considerable responsivity (≈82.97 mA W⁻¹), detectivity (≈8.06 ×10¹¹ Jones) under weak light (0.02 mW cm⁻²) irradiation, in the top rank of the reported hybrid bismuth halide perovskites. This finding offers novel design criterion for high-performance lead-free perovskites.

CBD-SnO₂ buried interface has been modified by a multifunctional molecule, MES-K, to passivate interfacial defects, tailor perovskite crystallization, release residual stress, and tune energy bands as well. A high PCE of 25.14% on 0.09 cm² device and 24.45% on 1 cm² device, with negligible hysteresis, are achieved with excellent storage and light illumination stability.

Abstract

Tin oxide (SnO₂) based on chemical bath deposition method (CBD-SnO₂) is considered as an ideal electron transporting layer for perovskite solar cells (PSCs), however, the research on precise regulation toward CBD-SnO₂ layer is lacking. Here, the study introduces a multifunctional molecule, potassium 2-(N-morpholino)ethanesulfonate (MES-K), on the surface of CBD-SnO₂ layer to synergistically modify the buried interface between the SnO₂ and perovskite. It is found that MES-K introduction can passivate interfacial defects, favor the perovskite crystal growth, and improve carrier transportation. 25.14% efficiency of small-size perovskite solar cells has been achieved with 24.45% efficiency of 1 cm² perovskite devices, with negligible hysteresis. Besides, unencapsulated devices based on CBD-SnO₂ can maintain > 95% of its initial efficiency after 2000 h storage at ambient environment, and > 90% after 1000 h LED illumination.

Functionalized 2D/3D heterojunction is constructed through reversible iodine-alkenes reaction in 3-butenylamine (BEA) based 2D perovskite (BEA)₂[PbBr₄]. (BEA)₂[PbBr₄] can adsorb photo-generated iodine species during perovskite degradation, inhibiting the iodine loss issue in PSCs. These adsorbed iodine can still react with Pb⁰, eliminating related defects. The resulting PSCs exhibit good operational stability without encapsulation, retaining ≈94% of initial efficiency after MPP tracking for 2000 h at 65 °C with ISOS-L-2 protocol.

Abstract

Long-term operational stability remains a big challenge for perovskite solar cells (PSCs), especially under ISOS protocol with high temperature. One key reason lies in the iodine loss issue during PSCs aging. Motived by the reversible iodine-alkenes reaction, 3-butenylamine (BEA) based 2D perovskite (BEA)₂[PbBr₄] is used to construct a functionalized 2D/3D heterojunction in PSCs. (BEA)₂[PbBr₄] can chemically adsorb photo-generated iodine species during perovskite degradation through a typical reaction between neutral iodine and terminal alkenes, thus inhibiting iodine loss or diffusion in PSCs. Besides, owing to the reversible reaction nature, these adsorbed iodine species can be partially released slowly under heat conditions, further reacting with and eliminating potential metallic Pb⁰ defects. The resulting PSCs exhibit a high efficiency of 24.5% with good operational stability even without encapsulation, retaining ≈94% of initial efficiency after MPP tracking for 2000 h at 65 °C with ISOS-L-2 protocol.

Recent research of narrow bandgap and wide bandgap PSCs to overcome the stability issue and achieve ameliorated performance. Optimization of both range of PSCs paved the way to all-perovskite tandem solar cell, which will be required with various strategies to overcome the confronting issues. In other word, optimizing both narrow and wide bandgap perovskite solar cell would ultimately contribute to higher achievement of all-perovskite tandem solar cell.

Abstract

As perovskite solar device is burgeoning photoelectronic device, numerous studies to optimize perovskite solar device have been demonstrated. Amongst various advantages from perovskite light absorbing layer, attractive property of tunable bandgap allowed perovskite to be adopted in many different fields. Easily tunable bandgap property of perovskite opened the wide application and to get the most out of its potential, many researchers contributed as well. By precursor composition engineering, narrow bandgap with bandgap of less than 1.4 eV and wide bandgap with bandgap of more than 1.7 eV were achieved. Optimization of both narrow and wide bandgap perovskite solar cell could pave the way to all-perovskite tandem solar cell which is combination of top cell with wide bandgap and bottom cell with narrow bandgap. This review highlights numerous efforts to advance device performance of both narrow and wide bandgap perovskite solar cell and how they challenged the issues. And finally, efforts to operate and utilize all-tandem perovskite device in real world will be discussed.

Most tandem cells reported to date have been realized on Si wafers with polished or nano-textured front surfaces to accommodate the perovskite film deposition by standard solution-based processes. To guarantee compatibility with the industrial Si wafers featuring micrometer pyramids, the main hurdle has been preparing high-quality perovskite film with minimized residual stresses. Here, a vertically 3D/3D strained heterostructure at the buried interface allows effective strain management, which improves film quality by promoting the desired crystal growth and suppressing defect formation.

The supersaturated point defects in perovskite films will generate during cooling process after annealing and its concentration improves as the cooling rate increases. These defects can be minimized through slowing the cooling rate. The resultant PSCs deliver a 25.47% PCE (certified 24.7%) and retain >90% of their initial value after >1100 h of operation at the maximum power point.

Abstract

Numerous efforts are devoted to reducing the defects at perovskite surface and/or grain boundary; however, the grown-in defects inside grain is rarely studied. Here, the influence of cooling rate on the point defects concentration in polycrystalline perovskite film during heat treatment processing is investigated. With the combination of theoretical and experimental studies, this work reveals that the supersaturated point defects in perovskite films generate during the cooling process and its concentration improves as the cooling rate increases. The supersaturated point defects can be minimized through slowing the cooling rate. As a result, the optimized FAPbI₃ polycrystalline films achieve a superior carrier lifetime of up to 12.6 µs and improved stability. The champion device delivers a 25.47% PCE (certified 24.7%) and retain 90% of their initial value after >1100 h of operation at the maximum power point. These results provide a fundamental understanding of the mechanisms of grown-in defects formation in polycrystalline perovskite film.

A framework based on thickness-dependent time-resolved photoluminescence spectroscopy is provided that allows bulk and surface lifetimes to be separated. The analysis is extended to calculate the surface recombination velocities of 18 contacts under standard and inverted configurations. The resolved implied open-circuit voltages of three devices are predicted using this framework, and compared with fully fabricated cells. With this analysis, it is shown that C₆₀ accounts for ≈90% of all recombination, while bulk losses are minimal in perovskite solar cells.

Abstract

Perovskite solar cells have reached an impressive certified efficiency of 26.1%, with a considerable fraction of the remaining losses attributed to carrier recombination at perovskite interfaces. This work demonstrates how time-resolved photoluminescence spectroscopy (TRPL) can be utilized to locate and quantify remaining recombination losses in perovskite solar cells, analogous to methods established to improve silicon solar cell passivation and contact layers. It is shown how TRPL analysis can be extended to determine the bulk and surface lifetimes, surface recombination velocity, the recombination parameter, J₀ , and the implied open-circuit voltage (iV_oc ) of any perovskite device configuration. This framework is used to compare 18 carrier-selective and passivating contacts commonly used or emerging for perovskite photovoltaics. Furthermore, the iV_oc values calculated from the TRPL-based framework are directly compared to those calculated from photoluminescence quantum yields and the measured solar cell V_oc . This simple technique serves as a practical guide for screening and selecting multifunctional, passivating perovskite contact layers. As with silicon solar cells, most of the material and interface analysis can be done without fabricating full devices or measuring efficiency. These purely optical measurements are even preferable when studying bulk and interfacial passivation approaches, since they remove complicating effects from poor carrier extraction.

The P3HT hole transport layer (HTL) featuring preferable three-dimension molecular orientation is realized via optimizing its preparation process. The preferable molecular orientation of P3HT HTL imparts improved electronic properties, enhanced moisture-repelling capability, intensified defect passivation, and matched energy level. The small-area (0.04 cm²) and large-area (1 cm²) carbon-electrode devices deliver notable efficiency of 20.55% and 18.32% with desirable stability.

Abstract

Carbon-based perovskite solar cells (PSCs) coupled with solution-processed hole transport layers (HTLs) have shown potential owing to their combination of low cost and high performance. However, the commonly used poly(3-hexylthiophene) (P3HT) semicrystalline-polymer HTL dominantly shows edge-on molecular orientation, in which the alkyl side chains directly contact the perovskite layer, resulting in an electronically poor contact at the perovskite/P3HT interface. The study adopts a synergetic strategy comprising of additive and solvent engineering to transfer the edge-on molecular orientation of P3HT HTL into 3D molecular orientation. The target P3HT HTL possesses improved charge transport as well as enhanced moisture-repelling capability. Moreover, energy level alignment between target P3HT HTL and perovskite layer is realized. As a result, the champion devices with small (0.04 cm²) and larger areas (1 cm²) deliver notable efficiencies of 20.55% and 18.32%, respectively, which are among the highest efficiency of carbon-electrode PSCs.

Publication date: September 2024

Source: Nano Energy, Volume 128, Part B

Author(s): Xin Meng, Xiaoxuan Liu, Qisen Zhou, Zonghao Liu, Wei Chen