JIANG ZHI XUAN

Publication date: January 2020

Source: Solar Energy Materials and Solar Cells, Volume 204

Author(s): Bhaskar Parida, Saemon Yoon, Sang Mun Jeong, Jung Sang Cho, Jae-Kwang Kim, Dong-Won Kang

Low‐cost n‐type goethite (FeOOH) quantum dots (QDs) are introduced into the perovskite light‐absorber layer to fabricate efficient and stable perovskite solar cells (PSCs). As a result, the PSCs with FeOOH QDs obtain a significant efficiency enhancement from 16.6% to 19.7%. Most strikingly, the long‐term stability of PSCs with FeOOH QDs is significantly enhanced.

Abstract

Minimization of defects and ion migration in organic–inorganic lead halide perovskite films is desirable for obtaining photovoltaic devices with high power conversion efficiency (PCE) and long‐term stability. However, achieving this target is still a challenge due to the lack of efficient multifunctional passivators. Herein, to address this issue, n‐type goethite (FeOOH) quantum dots (QDs) are introduced into the perovskite light‐absorption layer for achieving efficient and stable perovskite solar cells (PSCs). It is found that the iron, oxygen, and hydroxyl of FeOOH QDs can interact with iodine, lead, and methylamine, respectively. As a result, the crystallization kinetics process can be retarded, thereby resulting in high quality perovskite films with large grain size. Meanwhile, the trap states of perovskite can be effectively passivated via interaction with the under‐coordinated metal (Pb) cations, halide (I) anions on the perovskite crystal surface. Consequently, the PSCs with FeOOH QDs achieve a high efficiency close to 20% with negligible hysteresis. Most strikingly, the long‐term stability of PSCs is significantly enhanced. Furthermore, compared with the CH₃NH₃PbI₃‐based device, a higher PCE of 21.0% is achieved for the device assembled with a Cs_0.05FA_0.81MA_0.14PbBr_0.45I_2.55 perovskite layer.

Black phosphorous quantum dots are used as interlayers to modify both electron and hole transport layers in organic solar cells. The power conversion efficiencies of the nonfullerene and fullerene‐based devices are enhanced.

Abstract

Black phosphorous quantum dots (BPQDs) possess ambipolar charge transport, high mobility, and a tunable direct bandgap. Here, liquid‐exfoliated BPQDs are used as interlayers to modify both the electron transport layer and hole transport layer in organic solar cells (OSCs). The incorporation of BPQDs is beneficial to the formation of a cascade band structure and electron/hole transfer and extraction. The power conversion efficiency of the BPQDs‐incorporated OSC based on PTB7‐Th:FOIC blend is enhanced from 11.8% to 13.1%. In addition, power conversion efficiency enhancement is also achieved for other nonfullerene and fullerene‐based devices, demonstrating the universality of this interlayer methodology.

Publication date: January 2020

Source: Solar Energy Materials and Solar Cells, Volume 204

Author(s): Aleksandr Kovrov, Martin Helgesen, Christine Boeffel, Stefan Kröpke, Roar R. Søndergaard

A new doping strategy is developed for poly(3‐hexylthiophene) (P3HT) as the hole transport layer (HTL) in triple‐cation/double‐halide mesoscopic perovskite solar cells (PSCs), achieving efficiencies of 19.25% and 13.3% on lab‐scale and large‐area module, respectively. Promising stability results after 1500 h air exposure (relative humidity ≈ 60%, r.t.), more than 500 h at 85 °C, and 100 h of continuous light soaking.

Abstract

As the hole transport layer (HTL) for perovskite solar cells (PSCs), poly(3‐hexylthiophene) (P3HT) has been attracting great interest due to its low‐cost, thermal stability, oxygen impermeability, and strong hydrophobicity. In this work, a new doping strategy is developed for P3HT as the HTL in triple‐cation/double‐halide ((FA_1−x−yMA_xCs_y)Pb(I_1−xBr_x)₃) mesoscopic PSCs. Photovoltaic performance and stability of solar cells show remarkable enhancement using a composition of three dopants Li‐TFSI, TBP, and Co(III)‐TFSI reaching power conversion efficiencies of 19.25% on 0.1 cm² active area, 16.29% on 1 cm² active area, and 13.3% on a 43 cm² active area module without using any additional absorber layer or any interlayer at the PSK/P3HT interface. The results illustrate the positive effect of a cobalt dopant on the band structure of perovskite/P3HT interfaces leading to improved hole extraction and a decrease of trap‐assisted recombination. Non‐encapsulated large area devices show promising air stability through keeping more than 80% of initial efficiency after 1500 h in atmospheric conditions (relative humidity ≈ 60%, r.t.), whereas encapsulated devices show more than >500 h at 85 °C thermal stability (>80%) and 100 h stability against continuous light soaking (>90%). The boosted efficiency and the improved stability make P3HT a good candidate for low‐cost large‐scale PSCs.

CsPbI₂Br perovskite is doped by Eu(Ac)₃ to obtain high‐quality perovskite films with low defect density and long carrier lifetime. A high efficiency of 15.25%, an open‐circuit voltage of 1.25 V, a short‐circuit current density of 15.44 mA cm⁻², and a fill factor of 79.00% are realized for CsPbI₂Br solar cells. The devices with Eu(Ac)₃ doping demonstrate excellent air stability.

Abstract

All‐inorganic perovskite solar cells have developed rapidly in the last two years due to their excellent thermal and light stability. However, low efficiency and moisture instability limit their future commercial application. The mixed‐halide inorganic CsPbI₂Br perovskite with a suitable bandgap offers a good balance between phase stability and light harvesting. However, high defect density and low carrier lifetime in CsPbI₂Br perovskites limit the open‐circuit voltage (V _oc < 1.2 V), short‐circuit current density (J _sc < 15 mA cm⁻²), and fill factor (FF < 75%) of CsPbI₂Br perovskite solar cells, resulting in an efficiency below 14%. For the first time, a CsPbI₂Br perovskite is doped by Eu(Ac)₃ to obtain a high‐quality inorganic perovskite film with a low defect density and long carrier lifetime. A high efficiency of 15.25% (average efficiency of 14.88%), a respectable V _oc of 1.25 V, a reasonable J _sc of 15.44 mA cm⁻², and a high FF of 79.00% are realized for CsPbI₂Br solar cells. Moreover, the CsPbI₂Br solar cells with Eu(Ac)₃ doping demonstrate excellent air stability and maintain more than 80% of their initial power conversion efficiency (PCE) values after aging in air (relative humidity: 35–40%) for 30 days.

Nonfullerene acceptors‐based terpolymer, SMD2, is designed and synthesized to continuously fabricate high‐performance organic solar cell (OSC) modules, and multifunctional hole transport layers are developed, and applied to flexible modules via an all‐solution process. the flexible OSC modules fabricated in an industrial production line have a PCE of 5.25% (P _max = 419.6 mW) on an area of 80 cm².

Abstract

To ensure laboratory‐to‐industry transfer of next‐generation energy harvesting organic solar cells (OSCs), it is necessary to develop flexible OSC modules that can be produced on a continuous roll‐to‐roll basis and to apply an all‐solution process. In this study, nonfullerene acceptors (NFAs)‐based donor polymer, SMD2, is newly designed and synthesized to continuously fabricate high‐performance flexible OSC modules. Also, multifunctional hole transport layers (HTLs), WO₃/HTL solar bilayer HTLs, are developed and applied via an all‐solution process called “ProcessOne” into inverted structure. SMD2, the donor terpolymer, has a deep highest occupied molecular orbital (HOMO) level and can achieve a power conversion efficiency (PCE) of 11.3% with NFAs without any pre‐/post‐treatment because of its optimal balance between crystallinity and miscibility. Furthermore, the integration of multifunctional HTLs enables the recovery of the drop in open circuit voltage (V _OC) caused by a mismatch in energy levels between the deep HOMO level of the NFAs‐based bulk‐heterojunction layer and the solution‐processed HTLs. Also, the photostability under ultraviolet‐exposure necessary for “ProcessOne” is greatly improved because of the integration of multifunctional HTLs. Consequently, because of the synergistic effects of these approaches, the flexible OSC modules fabricated in an industrial production line have a PCE of 5.25% (P _max = 419.6 mW) on an active area of 80 cm².

Inorganic halide perovskite quantum dots (IHPQDs) exhibit unique photoelectric properties and have aroused great interest in a wide range of applications. This review mainly presents the recent advances of IHPQDs for photoelectrochemical applications including photocatalytic CO₂ reduction, photocatalytic degradation, photocatalytic oxidation, photocatalytic polymerization, photoelectrochemical sensing, and solar cells.

Abstract

Inorganic halide perovskite quantum dots (IHPQDs) have recently emerged as a new class of optoelectronic nanomaterials that can outperform the existing hybrid organometallic halide perovskite (OHP), II–VI and III–V groups semiconductor nanocrystals, mainly due to their relatively high stability, excellent photophysical properties, and promising applications in wide‐ranging and diverse fields. In particular, IHPQDs have attracted much recent attention in the field of photoelectrochemistry, with the potential to harness their superb optical and charge transport properties as well as spectacular characteristics of quantum confinement effect for opening up new opportunities in next‐generation photoelectrochemical (PEC) systems. Over the past few years, numerous efforts have been made to design and prepare IHPQD‐based materials for a wide range of applications in photoelectrochemistry, ranging from photocatalytic degradation, photocatalytic CO₂ reduction and PEC sensing, to photovoltaic devices. In this review, the recent advances in the development of IHPQD‐based materials are summarized from the standpoint of photoelectrochemistry. The prospects and further developments of IHPQDs in this exciting field are also discussed.

A donor derivative is incorporated in benzodithiophene terthiophene rhodanine (BTR)‐based thick‐film all‐small‐molecule (ASM) organic solar cells (OSC), which achieves power conversion efficiency of 10.14% and fill factor of 74.2%, outperforms its binary counterparts, and stands the record value for thick‐film dual‐donor ternary ASM OSCs. The results demonstrate that the donor derivative is a promising third component to boost the performance of ASM OSCs.

Abstract

Thick‐film all‐small‐molecule (ASM) organic solar cells (OSCs) are preferred for large‐scale fabrication with printing techniques due to the distinct advantages of monodispersion, easy purification, and negligible batch‐to‐batch variation. However, ASM OSCs are typically constrained by the morphology aspect to achieve high efficiency and maintain thick film simultaneously. Specifically, synchronously manipulating crystallinity, domain size, and phase segregation to a suitable level are extremely challenging. Herein, a derivative of benzodithiophene terthiophene rhodanine (BTR) (a successful small molecule donor for thick‐film OSCs), namely, BTR‐OH, is synthesized with similar chemical structure and absorption but less crystallinity relative to BTR, and is employed as a third component to construct BTR:BTR‐OH:PC₇₁BM ternary devices. The power conversion efficiency (PCE) of 10.14% and fill factor (FF) of 74.2% are successfully obtained in ≈300 nm OSC, which outperforms BTR:PC₇₁BM (9.05% and 69.6%) and BTR‐OH:PC₇₁BM (8.00% and 65.3%) counterparts, and stands among the top values for thick‐film ASM OSCs. The performance enhancement results from the enhanced absorption, suppressed bimolecular/trap–assisted recombination, improved charge extraction, optimized domain size, and suitable crystallinity. These findings demonstrate that the donor derivative featuring similar chemical structure but different crystallinity provides a promising third component guideline for high‐performance ternary ASM OSCs.

Inorganic halide perovskite quantum dots (IHPQDs) exhibit unique photoelectric properties and have aroused great interest in a wide range of applications. This review mainly presents the recent advances of IHPQDs for photoelectrochemical applications including photocatalytic CO₂ reduction, photocatalytic degradation, photocatalytic oxidation, photocatalytic polymerization, photoelectrochemical sensing, and solar cells.

Abstract

Inorganic halide perovskite quantum dots (IHPQDs) have recently emerged as a new class of optoelectronic nanomaterials that can outperform the existing hybrid organometallic halide perovskite (OHP), II–VI and III–V groups semiconductor nanocrystals, mainly due to their relatively high stability, excellent photophysical properties, and promising applications in wide‐ranging and diverse fields. In particular, IHPQDs have attracted much recent attention in the field of photoelectrochemistry, with the potential to harness their superb optical and charge transport properties as well as spectacular characteristics of quantum confinement effect for opening up new opportunities in next‐generation photoelectrochemical (PEC) systems. Over the past few years, numerous efforts have been made to design and prepare IHPQD‐based materials for a wide range of applications in photoelectrochemistry, ranging from photocatalytic degradation, photocatalytic CO₂ reduction and PEC sensing, to photovoltaic devices. In this review, the recent advances in the development of IHPQD‐based materials are summarized from the standpoint of photoelectrochemistry. The prospects and further developments of IHPQDs in this exciting field are also discussed.