Unraveling Sunlight by Transparent Organic Semiconductors toward Photovoltaic and Photosynthesis

Liu, Yuan; Cheng, Pei; Li, Tengfei; Wang, Rui; Li, Yaowen; Chang, Sheng Yung; Zhu, Yuan; Cheng, Hsin-Pai; Wei, Kung‐Hwa; Zhan, Xiaowei; Sun, Baoquan; Yang, Yang

doi:10.1021/acsnano.8b08577

Cited by 147 publications

(134 citation statements)

References 40 publications

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“…The careful tuning of the reflection and transmission of the selected wavelengths presents a difficult challenge in both device engineering and material design. To date, the best performing flexible semitransparent single‐junction OSCs exhibits PCE of 10% at AVT of 34% …”

Section: Device Performance Limits Of Semitransparent Oscsmentioning

confidence: 99%

Solution‐Processed Semitransparent Organic Photovoltaics: From Molecular Design to Device Performance

et al. 2019

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Recent research efforts on solution-processed semitransparent organic solar cells (OSCs) are presented. Essential properties of organic donor:acceptor bulk heterojunction blends and electrode materials, required for the combination of simultaneous high power conversion efficiency (PCE) and average visible transmittance of photovoltaic devices, are presented from the materials science and device engineering points of view. Aspects of optical perception, charge generation-recombination, and extraction processes relevant for semitransparent OSCs are also discussed in detail. Furthermore, the theoretical limits of PCE for fully transparent OSCs, compared to the performance of the best reported semitransparent OSCs, and options for further optimization are discussed. Hall of Fame ArticleAlthough the last decade has seen much progress in the field of OSC research, the development of semitransparent devices lags behind because of the lack of optimized photoactive materials. [22][23][24][25] The strong absorption of the active materials in the visible region causes difficulty when one tries to balance the power conversion efficiency (PCE) and transmittance. Encouragingly, the recent progress of fullerene-free OSCs has the potential to shed fundamental solutions to overcome these obstacles, hence becoming attractive research topics on developing narrow-bandgap nonfullerene acceptors to researchers. [26][27][28][29][30] We focus in this section on presenting recent progress in the design of narrow-bandgap organic semiconductors that have bandgaps less than 1.5 eV and have extended the boundaries of visible transparent/NIR absorbing OSC technology. Solution-Processable Organic SemiconductorsOrganic semiconductors are carbon-based materials with an electronically delocalized π-conjugated backbone. Such π-conjugated systems are created by a linear series of overlapping p z orbitals (π bonds). [31,32] As the parallel overlap of carbon p z orbitals increases with the molecular extension, the π bonds may further spread out into π bands, and this leads to a narrower energy bandgap. The energy of the highest occupied molecular orbital (HOMO) corresponds to the topmost π band, and the lowest π* band is referred to as the lowest unoccupied molecular orbital (LUMO). The energy gap between the HOMO and the LUMO dominates optical properties. Photoexcitations result in Coulombically bound excitons (electron-hole pairs) due to the low dielectric constant (ε ≈ 2−4) characteristic of organic semiconductors. [33,34] The exciton binding energy is in the range of 0.3−1 eV, thus requiring a high interfacial area between electron donor (D) and electron acceptor (A) components to promote exciton dissociation into free carriers. [35,36] This approach has led to the development of organic bulk heterojunctions (BHJs), which are cast from blend solutions of D and A components. [37][38][39] The excitonic nature of organic semiconductors offers an advantage in wavelength-specific light harvesting applications through a delicate manipulation of energy ...

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Section: Device Performance Limits Of Semitransparent Oscsmentioning

confidence: 99%

Solution‐Processed Semitransparent Organic Photovoltaics: From Molecular Design to Device Performance

et al. 2019

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“…[60] The chemical structures of the materials used in this research are depicted in Figure 1b. [62][63][64] Unfortunately, this binary system presents pronounced performance degradation (≈35%) after storing the solar cells in a N 2 -filled glovebox for 90 days. [61] This result was achieved mainly through careful molecular engineering of the IEICO-4F small molecule acceptor and morphology control, which has enabled to harvest a large portion of the near-infrared solar energy.…”

mentioning

confidence: 99%

Rational Strategy to Stabilize an Unstable High‐Efficiency Binary Nonfullerene Organic Solar Cells with a Third Component

Zhu

Gadisa

Peng

et al. 2019

Advanced Energy Materials

141

143

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decades, heuristic approaches have been successfully used to enhance the performance of OSCs, including synthesis of new donor and acceptor molecules, [5][6][7][8][9][10] optimization of the interface and morphology, [11][12][13][14][15] ternary blending, [16][17][18][19] and device engineering. [20][21][22][23] As a result, power conversion efficiency (PCE) of OSCs has surpassed 15% for single-layer bulkheterojunction systems. [24,25] As the PCE of OSCs is getting closer to the requirements for commercial applications and competing technology, the most efficient OSCs also need to perform consistently or maintain low efficiency loss throughout their lifetimes. [26][27][28] To make organic photovoltaics commercially viable and competitive, researchers have been making efforts on characterizing, understanding, and rationally engineering the long-term stability of OSC devices. [26,[29][30][31][32][33][34][35][36][37][38] Generally, the performance degradation of OSCs comes from the oxidation of electrodes, degradation of the interface layers, and changes in the morphology of the active layer. Among these factors, the oxidation of electrodes and the degradation of the interface layers are attributed to exposure to oxygen and moisture, [39,40] and these drawbacks can be largely prevented by encapsulation. [41,42] However, the intrinsic instability of active layer morphology driven by light, temperature, and thermodynamics cannot be prevented by encapsulation. In-depth studies were carried out to understand the stability of the active layers under multiple stresses. [43] For instance, McGehee and co-workers [29] reported that solar cells based on amorphous materials would suffer from open-circuit voltage (V OC ) burnin degradation resulted from the impact of light-induced traps, and this degradation can be reduced by using materials with high degree of crystallinity. Brabec group [33] demonstrated that the light-induced [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) dimerization would lead to the short-circuit current density (J SC ) loss after aging, while this dimerization can be inhibited by a high degree of polymer-fullerene mixing and it can also be reduced via increasing the crystallization of the fullerene domains. Brabec and co-workers [34] found that burnin degradation driven by low miscibility is the major short-time Long device lifetime is still a missing key requirement in the commercialization of nonfullerene acceptor (NFA) organic solar cell technology. Understanding thermodynamic factors driving morphology degradation or stabilization is correspondingly lacking. In this report, thermodynamics is combined with morphology to elucidate the instability of highly efficient PTB7-Th:IEICO-4F binary solar cells and to rationally use PC 71 BM in ternary solar cells to reduce the loss in the power conversion efficiency from ≈35% to <10% after storage for 90 days and at the same time improve performance. The hypomiscibility observed for IEICO-4F in PTB7-Th (below the percolation threshold) leads to overpurific...

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“…[ 15–18 ] To date, the highest reported PCE for flexible ST‐OSCs with average visible light transmittance (AVT) of over 20% was just over 10%. [ 19 ] Greater attentions should be focused on the development of flexible ST‐OSCs due to its promising potentials as power‐generating windows/roofs in building‐integrated photovoltaics and photovoltaic vehicles. Additionally, one needs to consider the foldability properties of flexible ST‐OSCs if advanced applications in 3D curved surfaces (e.g., future foldable roofs in multifunctional self‐powered greenhouse) are to be realized.…”

Section: Figurementioning

confidence: 99%

Foldable Semitransparent Organic Solar Cells for Photovoltaic and Photosynthesis

Song

Fanady

Peng

et al. 2020

Advanced Energy Materials

128

102

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solution-processability, and lightweight property. [1][2][3][4][5][6] Recently, the power conversion efficiency (PCE) of a single-junction device based on binary photoactive layer system had surpassed the 15-16% boundaries for opaque OSCs and 11-12% boundaries for semitransparent OSCs (ST-OSCs), all of which were fabricated on rigid glass substrates. [7][8][9][10][11][12][13][14] Though the PCE had increased remarkably on rigid glass substrates, development of OSCs on flexible substrates particularly for flexible ST-OSCs still lagged behind. [15][16][17][18] To date, the highest reported PCE for flexible ST-OSCs with average visible light transmittance (AVT) of over 20% was just over 10%. [19] Greater attentions should be focused on the development of flexible ST-OSCs due to its promising potentials as power-generating windows/roofs in building-integrated photovoltaics and photovoltaic vehicles. Additionally, one needs to consider the foldability properties of flexible ST-OSCs if advanced applications in 3D curved surfaces (e.g., future foldable roofs in multifunctional selfpowered greenhouse) are to be realized. This situation drove the current works for foldable-flexible ST-OSCs (hereafter referred to as FST-OSCs).Over the years, studies on ST-OSCs and/or FST-OSCs have centered around materials design of the photoactive layer (design of novel donor/acceptor). [6,20,21] Generally, photo active layer is designed to readily absorb solar irradiation in the nearinfrared (NIR) to infrared (IR) region while being partially transparent in the visible light region. These IR-absorbing photoactive layers are particularly favorable for agricultural applications (e.g., common greenhouse) as sunlight in the visible light region can be predominantly transmitted for plants growth. In fact, solar irradiation located in the visible light region (370-740 nm) is mostly responsible for photosynthesis processes in plants for growth. [22] Through this, ST-OSCs and/ or FST-OSCs for photovoltaic and photosynthesis can be realized, proving the future potential of semitransparent devices as windows/roofs in multifunctional self-powered greenhouse.FST-OSCs have several key parameters similar to its rigid counterparts, such as efficiency, transparency, color, and color rendering property. The main distinct feature of FST-OSCs is its mechanical stability against extreme mechanical Semitransparent organic solar cells (ST-OSCs) have attracted extensive attention for their potential greenhouse applications. Conventional ST-OSCs are typically based on indium tin oxide (ITO) electrodes which suffer from mechanical brittleness. Therefore, alternatives for ITO are required for realization of foldable-flexible ST-OSCs (FST-OSCs). Herein, flexible poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) electrodes are prepared as ITO alternatives via polyhydroxy compound (xylitol) microdoping and acid treatment. As a result, flexible opaque OSCs based on PBDB-T-2F:Y6 photoactive system yield a high efficiency of 14.20%. The desirable optic...

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Unraveling Sunlight by Transparent Organic Semiconductors toward Photovoltaic and Photosynthesis

Cited by 147 publications

References 40 publications

Solution‐Processed Semitransparent Organic Photovoltaics: From Molecular Design to Device Performance

Solution‐Processed Semitransparent Organic Photovoltaics: From Molecular Design to Device Performance

Rational Strategy to Stabilize an Unstable High‐Efficiency Binary Nonfullerene Organic Solar Cells with a Third Component

Foldable Semitransparent Organic Solar Cells for Photovoltaic and Photosynthesis

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