Atomically Thin-Layered Molybdenum Disulfide (MoS₂) for Bulk-Heterojunction Solar Cells

Singh, Eric,Kim, Ki Seok,Yeom, Geun Young,Nalwa, Hari Singh American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.4

<P>Transition metal dichalcogenides (TMDs) are becoming significant because of their interesting semiconducting and photonic properties. In particular, TMDs such as molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2), tungsten disulfide (WS2), tungsten diselenide (WSe2), titanium disulfide (TiS2), tantalum sulfide (TaS2), and niobium selenide (NbSe2) are increasingly attracting attention for their applications in solar cell devices. In this review, we give a brief introduction to TMDs with a focus on MoS2; and thereafter, emphasize the role of atomically thin MoS2 layers in fabricating solar cell devices, including bulk-heterojunction, organic, and perovskites-based solar cells. Layered MoS2 has been used as the hole-transport layer (HTL), electron-transport layer (ETL), interfacial layer, and protective layer in fabricating heterojunction solar cells. The trilayer graphene/MoS2/n-Si solar cell devices exhibit a power-conversion efficiency of 11.1%. The effects of plasma and chemical doping on the photovoltaic performance of MoS2 solar cells have been analyzed. After doping and electrical gating, a power-conversion efficiency (PCE) of 9.03% has been observed for the MoS2/h-BN/GaAs heterostructure solar cells. The MoSrcontaining perovskites-based solar cells show a PCE as high as 13.3%. The PCE of MoS2-based organic solar cells exceeds 8.40%. The stability of MoS2 solar cells measured under ambient conditions and light illumination has been discussed. The MoS2-based materials show a great potential for solar cell devices along with high PCE; however, in this connection, their long-term environmental stability is also of equal importance for commercial applications.</P>

Recent Advances in the Determination of Optimal Active Layer Thickness for Bulk Heterojunction Organic Solar Cells

Sakshi Koul,Najeeb-ud-din Hakim 한국전기전자재료학회 2018 Transactions on Electrical and Electronic Material Vol.19 No.5

Organic solar cells have gathered much research interest in recent years because of their advantages like low-cost, fl exibilityand light-weight. This paper presents a fi rst of its kind, critical review of the theoretical and experimental studies performedto determine the outcome of changing active layer thickness on the working of a bulk heterojunction organic solar cell. Thefunctional principles of an organic solar cell along with its typical parameters are briefl y outlined. This paper discusses thefeatures of the active layer and response of these features to changing active layer thickness which determines the deviceperformance. Subsequently we describe the changes occurring in the parameters of the solar cell, followed by a detailedaccount of the optimal thickness ranges for diff erent bulk heterojunction solar cells. A concise description of the donor andacceptor material properties is also presented. In the last section, simulations performed by changing active layer thicknessfor two diff erent active layer material combinations have been presented, wherein we used poly(3-hexylthiophene): P3HT asthe electron donor and phenyl-C 61 -butyric acid methyl ester: PCBM as the electron acceptor for one cell and the other cellhas poly(9,9-dioctylindenofl uorene- co -benzothiadiazole): PIF8BT and N ′-bis(1-ethylpropyl)-3,4,9,10-perylene tetracarboxydiimide: PDI as donor and acceptor respectively. The paper concludes with a brief discussion of the applicability of annealingprocess to improve the optimal active layer thickness ranges of organic solar cells.

Synergistic photocurrent addition in hybrid quantum dot: Bulk heterojunction solar cells

Kim, Gi-Hwan,Walker, Bright,Zhitomirsky, David,Heo, Jungwoo,Ko, Seo-Jin,Park, Jongnam,Sargent, Edward H.,Young Kim, Jin Elsevier 2015 Nano energy Vol.13 No.-

<P><B>Abstract</B></P> <P>We investigate the effect of a thin PbS quantum dot (QD) layer on the performance of hybrid quantum-dot-organic solar cells (QD-OSCs). The PbS QD layer is able to function as a photosensitizing layer to improve short circuit current density (<I>J</I> <SUB>SC</SUB>) and power conversion efficiency (PCE) by exploiting solar flux in the near infrared region up to 1100nm. The increase in <I>J</I> <SUB>SC</SUB> is well represented by changes observed in the external quantum efficiency of devices with and without the PbS QD layer, including the region of the first exciton transition where only the PbS QD layer absorbs. Remarkably, enhanced performance was observed in QD-OSCs consisting of just a 13nm thick PbS QD layer and 150nm PTB7:PC<SUB>71</SUB>BM layer, exhibiting a <I>J</I> <SUB>SC</SUB> of 17.0mAcm<SUP>−2</SUP>, and PCE of 8.30% (8.58% for champion device) compared to reference devices without PbS QD which produced a <I>J</I> <SUB>SC</SUB> of 15.4mAcm<SUP>−2</SUP> and PCE of 7.56%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We have fabricated hybrid solar cells using a PbS QD layer and PTB7/PC<SUB>71</SUB>BM layer. </LI> <LI> The device is built on PTB7:PC<SUB>71</SUB>BM bulk heterojunction and a PbS QD layer. </LI> <LI> The PbS QD layer acts as a photosensitizing layer to improve the device performance. </LI> <LI> Additional photocurrent leads to enhancement in performance in hybrid solar cells. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The effect of a thin PbS quantum dot (QD) layer on the performance of hybrid quantum-dot-organic solar cells (QD-OSCs) was investigated. The PbS QD layer is able to function as a photosensitizing layer with PTB7/PC<SUB>71</SUB>BM bulk heterojunction to improve short circuit current density from 15.4mAcm<SUP>−2</SUP> to 17.0mAcm<SUP>−2</SUP> and power conversion efficiency from 7.56% to 8.30%. </P> <P>[DISPLAY OMISSION]</P>

Enhanced performance of termary bulk heterojunction solar cells by introducing energy transfer polymer

유준영,한용운,허수원,문두경 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.1

Polymer solar cells(PSCs) have been regarded as important source of energy because of their low cost, solution processibility and possibility of flexible solar cells. However, relatively narrow absorption spectrum of donor polymer is one of the major limitations of PSCs. In this study, we introduced different band gap polymer compared with donor polymer in active layer to overcome limitation. This structure called ternary bulk heterojunction can occur energy transfer because emission spectrum of donor polymer and absorption spectrum of another polymer are overlapped. PSCs were fabricated with energy transfer polymer forming ternary bulk heterojunction structure and control device. Consequently, absorption spectrum of active layer was expended and the photovoltaic performance of ternary bulk heterojunction solar cells was enhanced.

Naphtho[2,1‐<i>b</i>:3,4‐<i>b</i>′]dithiophene‐based Bulk Heterojunction Solar Cells: How Molecular Structure Influences Nanoscale Morphology and Photovoltaic Properties

Kim, Yu Jin,Cheon, Ye Rim,Back, Jang Yeol,Kim, Yun‐,Hi,Chung, Dae Sung,Park, Chan Eon WILEY‐VCH Verlag 2014 ChemPhysChem Vol.15 No.16

<P><B>Abstract</B></P><P>Organic bulk heterojunction photovoltaic devices based on a series of three naphtho[2,1‐<I>b</I>:3,4‐<I>b</I>′]dithiophene (NDT) derivatives blended with phenyl‐C<SUB>71</SUB>‐butyric acid methyl ester were studied. These three derivatives, which have NDT units with various thiophene‐chain lengths, were employed as the donor polymers. The influence of their molecular structures on the correlation between their solar‐cell performances and their degree of crystallization was assessed. The grazing‐incidence angle X‐ray diffraction and atomic force microscopy results showed that the three derivatives exhibit three distinct nanoscale morphologies. We correlated these morphologies with the device physics by determining the <I>J</I>–<I>V</I> characteristics and the hole and electron mobilities of the devices. On the basis of our results, we propose new rules for the design of future generations of NDT‐based polymers for use in bulk heterojunction solar cells.</P>

Degradation of fill factor in P3HT:PCBM based organic solar cells

Vinamrita Singh 한국물리학회 2017 Current Applied Physics Vol.17 No.11

In this paper, the degradation of fill factor with time of organic bulk heterojunction solar cells has been investigated up to 312 h. The experimental data of P3HT:PCBM solar cells has been analyzed theoretically to determine the parameters which affect the FF. The existing empirical formula has been applied to degradation data, and it was found to deviate drastically as the cell degrades, indicating that the correct behavior of solar cell is not imitated using the current FF formula. In view of the discrepancy, the expression for fill factor has been modified taking into account the material and device properties, which directly influence the working of a solar cell. All the values can be determined experimentally. The results of the modified expression gives better theoretical fit of FF with time. The results highlight the parameters which should be targeted in order to overcome the short lifetime of organic solar cells.

Optimized phase separation in low-bandgap polymer:fullerene bulk heterojunction solar cells with criteria of solvent additives

Choi, Youna,Kim, Geunjin,Kim, Heejoo,Lee, Seoung Ho,Kwon, Sooncheol,Kim, Junghwan,Lee, Kwanghee Elsevier 2016 Nano energy Vol.30 No.-

<P><B>Abstract</B></P> <P>We investigate a correlation between the type of solvent additives (SAs) with specific criteria such as aromatic additives (AAs) and non-aromatic additives (NAAs) and phase separation in the bulk heterojunction (BHJ) films comprising low-band gap polymer and fullerene derivatives. When AAs are used as SAs, the geometrical structures (π-π and lamellar stacking) of aggregated polymer chains do not significantly change. However, NAAs increase the lamellar stacking distance through a strong interaction with non-aromatic segments of polymers. Therefore, a well-phase separated BHJ morphology with the finer fibrils is developed, thereby leading to balanced charge mobilities and a reduced charge recombination in BHJ solar cells. Finally, the optimized solar cell exhibits a high power conversion efficiency of 7.9%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We investigated the correlation between the phase separation in BHJ films and SA types with specific criteria (AAs and NAAs). </LI> <LI> A well-phase separated nano-morphology with balanced charge mobilities was obtained in the BHJ films processed with NAAs. </LI> <LI> This result would be helpful in determining suitable SAs for newly synthesized π-CP systems. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The correlation between the type of solvent additives with specific criteria such as aromatic additives (AAs) and non-aromatic additives (NAAs) and phase separation in the bulk heterojunction (BHJ) films is investigated. By strong interaction between NAAs and non-aromatic segment of polymers, a well-phase separated BHJ morphology with the finer fibrils is developed, thereby leading to balanced charge mobilities and a reduced charge recombination in BHJ solar cells.</P> <P>[DISPLAY OMISSION]</P>

Ternary Blend Composed of Two Organic Donors and One Acceptor for Active Layer of High-Performance Organic Solar Cells

Lee, Jong Won,Choi, Yoon Suk,Ahn, Hyungju,Jo, Won Ho American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.17

<P>Ternary blends composed of two donor absorbers with complementary absorptions provide an opportunity to enhance the short-circuit current and thus the power conversion efficiency (PCE) of organic solar cells. In addition to complementary absorption of two donors, ternary blends may exhibit favorable morphology for high-performance solar cells when one chooses properly the donor pair. For this purpose, we develop a ternary blend with two donors (diketopyrrolopyrrole-based polymer (PTDPP2T) and small molecule ((TDPP)(2)Ph)) and one acceptor (PC71BM). The solar cell made of a ternary blend with 10 wt % (TDPP)(2)Ph exhibits higher PCE of 7.49% as compared with the solar cells with binary blends, PTDPP2T:PC71BM (6.58%) and (TDPP)(2)Ph:PC71BM (3.21%). The higher PCE of the ternary blend solar cell is attributed mainly to complementary absorption of two donors. However, a further increase in (TDPP)(2)Ph content in the ternary blend (>10 wt %) decreases the PCE. The ternary blend with 10 wt % (TDPP)(2)Ph exhibits well-developed morphology with narrow-sized fibrils while the blend with 15 wt % (TDPP)(2)Ph shows phase separation with large-sized domains, demonstrating that the phase morphology and compatibility of ternary blend are important factors to achieve a high-performance solar cell made of ternary blends.</P>

Tailored Morphology Control of Rapid Drying Blade-coated Organic Solar Cells

정요섭,정재웅 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

The printable solar cells are the most attracting photovoltaic technologies suitable for large area and low-temperature processing. The state-of-the-art organic solar cells achieve power conversion efficiency higher than 16% via spin coating of a polymer donor and a nonfullerene acceptor. However, the spin coating is an uneconomical process because the amount of solution used is very large compared to the coating area. In addition, the uniform film area from spin coating is limited. In this regard, we herein investigate uniform film coating of a blend of polymer donor and non-fullerene acceptor via blade coating with controlled solution temperature. We demonstrate that the chilled solution of a polymer donor and a non-fullerene acceptor facilitates self-assembly of the conjugated molecules, which significantly improves optoelectronic properties of the blend film. The optimized bulk heterojunction morphology led to promising power conversion efficiency of 11.22% of organic solar cells.

Organic solar cells based on conjugated polymers : History and recent advances

김화정,김영규,남성호,정재훈,이수용,서주역,한혜미 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.7

Organic solar cells have attracted huge attention because of their potential in the low-cost manufacturingof plastic solar modules featuring flexible, lightweight, ultrathin, rollable and bendable shapes. The power conversionefficiency of organic solar cells is now passing ~10%, which is a critical sign toward commercialization becauseorganic solar cells surpass any other types of solar cells in terms of development speed. The encouraging efficiencyenhancement could be realized by introducing a ‘bulk heterojunction’ concept that overcomes the weakness of organicsemiconductors by minimizing their charge transport paths through making effective p-n junctions inside bulk organicfilms. However, there are several hurdles for commercialization, including stability and lifetime issues, owing to thebulk heterojunction concept. This review summarizes the important aspects of organic solar cells, particularly focusingon conjugated polymers as an active layer component.