In organic solar cells (OSCs), cathode interfacial materials are generally designed with highly polar groups to increase the capability of lowering the work function of cathode. However, the strong ...polar group could result in a high surface energy and poor physical contact at the active layer surface, posing a challenge for interlayer engineering to address the trade-off between device stability and efficiency. Herein, we report a hydrogen-bonding interfacial material, aliphatic amine-functionalized perylene-diimide (PDINN), which simultaneously down-shifts the work function of the air stable cathodes (silver and copper), and maintains good interfacial contact with the active layer. The OSCs based on PDINN engineered silver-cathode demonstrate a high power conversion efficiency of 17.23% (certified value 16.77% by NREL) and high stability. Our results indicate that PDINN is an effective cathode interfacial material and interlayer engineering via suitable intermolecular interactions is a feasible approach to improve device performance of OSCs.
Low bandgap n-type organic semiconductor (n-OS) ITIC has attracted great attention for the application as an acceptor with medium bandgap p-type conjugated polymer as donor in nonfullerene polymer ...solar cells (PSCs) because of its attractive photovoltaic performance. Here we report a modification on the molecular structure of ITIC by side-chain isomerization with meta-alkyl-phenyl substitution, m-ITIC, to further improve its photovoltaic performance. In a comparison with its isomeric counterpart ITIC with para-alkyl-phenyl substitution, m-ITIC shows a higher film absorption coefficient, a larger crystalline coherence, and higher electron mobility. These inherent advantages of m-ITIC resulted in a higher power conversion efficiency (PCE) of 11.77% for the nonfullerene PSCs with m-ITIC as acceptor and a medium bandgap polymer J61 as donor, which is significantly improved over that (10.57%) of the corresponding devices with ITIC as acceptor. To the best of our knowledge, the PCE of 11.77% is one of the highest values reported in the literature to date for nonfullerene PSCs. More importantly, the m-ITIC-based device shows less thickness-dependent photovoltaic behavior than ITIC-based devices in the active-layer thickness range of 80–360 nm, which is beneficial for large area device fabrication. These results indicate that m-ITIC is a promising low bandgap n-OS for the application as an acceptor in PSCs, and the side-chain isomerization could be an easy and convenient way to further improve the photovoltaic performance of the donor and acceptor materials for high efficiency PSCs.
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IJS, KILJ, NUK, PNG, UL, UM
Abstract
Considering their superior charge-transfer characteristics, easy tenability of energy levels, and low production cost, organic semiconductors are ideal for photoelectrochemical (PEC) ...hydrogen production. However, organic-semiconductor-based photoelectrodes have not been extensively explored for PEC water-splitting because of their low stability in water. Herein, we report high-performance and stable organic-semiconductors photoanodes consisting of
p
-type polymers and
n
-type non-fullerene materials, which is passivated using nickel foils, GaIn eutectic, and layered double hydroxides as model materials. We achieve a photocurrent density of 15.1 mA cm
−2
at 1.23 V vs. reversible hydrogen electrode (RHE) with an onset potential of 0.55 V vs. RHE and a record high half-cell solar-to-hydrogen conversion efficiency of 4.33% under AM 1.5 G solar simulated light. After conducting the stability test at 1.3 V vs. RHE for 10 h, 90% of the initial photocurrent density are retained, whereas the photoactive layer without passivation lost its activity within a few minutes.
Simutaneously high open circuit voltage and high short circuit current density is a big challenge for achieving high efficiency polymer solar cells due to the excitonic nature of organic ...semdonductors. Herein, we developed a trialkylsilyl substituted 2D-conjugated polymer with the highest occupied molecular orbital level down-shifted by Si-C bond interaction. The polymer solar cells obtained by pairing this polymer with a non-fullerene acceptor demonstrated a high power conversion efficiency of 11.41% with both high open circuit voltage of 0.94 V and high short circuit current density of 17.32 mA cm
benefitted from the complementary absorption of the donor and acceptor, and the high hole transfer efficiency from acceptor to donor although the highest occupied molecular orbital level difference between the donor and acceptor is only 0.11 eV. The results indicate that the alkylsilyl substitution is an effective way in designing high performance conjugated polymer photovoltaic materials.
Flexible and stretchable organic solar cells (OSCs) have attracted enormous attention due to their potential applications in wearable and portable devices. To achieve flexibility and stretchability, ...many efforts have been made with regard to mechanically robust electrodes, interface layers, and photoactive semiconductors. This has greatly improved the performance of the devices. State‐of‐the‐art flexible and stretchable OSCs have achieved a power conversion efficiency of 15.21% (16.55% for tandem flexible devices) and 13%, respectively. Here, the recent progress of flexible and stretchable OSCs in terms of their components and processing methods are summarized and discussed. The future challenges and perspectives for flexible and stretchable OSCs are also presented.
The recent progress in flexible and stretchable organic solar cells (OSCs) is discussed. For flexible OSCs, the features of the commonly used flexible transparent electrodes and the relevant performance are selectively summarized and discussed. For stretchable OSCs, both the nonintrinsic and intrinsic processing methods are presented and discussed.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
All‐polymer solar cells (all‐PSCs) offer unique morphology stability for the application as flexible devices, but the lack of high‐performance polymer acceptors limits their power conversion ...efficiency (PCE) to a value lower than those of the PSCs based on fullerene derivative or organic small molecule acceptors. We herein demonstrate a strategy to synthesize a high‐performance polymer acceptor PZ1 by embedding an acceptor–donor–acceptor building block into the polymer main chain. PZ1 possesses broad absorption with a low band gap of 1.55 eV and high absorption coefficient (1.3×105 cm−1). The all‐PSCs with the wide‐band‐gap polymer PBDB‐T as donor and PZ1 as acceptor showed a record‐high PCE of 9.19 % for the all‐PSCs. The success of our polymerization strategy can provide a new way to develop efficient polymer acceptors for all‐PSCs.
Energy conversion: Embedding an acceptor–donor–acceptor‐structured organic semiconductor building block into a polymer main chain creates an excellent low‐band‐gap polymer acceptor with red‐shifted absorption and a high absorption coefficient. The polymer acceptor provides a record‐high power conversion efficiency of 9.19 % for all‐polymer solar cells.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Finding effective molecular design strategies to enable efficient charge generation and small energy loss is among the long-standing challenges in developing high performance non-fullerene organic ...solar cells (OSCs). Recently, we reported Y-series non-fullerene acceptors with an electron-deficient-core-based fused structure (typically Y6), opening a new door to achieve high external quantum efficiency (∼80%) while maintaining low energy loss (∼0.57 eV). On this basis, further reducing the energy losses and ultimately improving the performance of OSCs has become a research hotspot. In this paper, we design and synthesize a new member of the Y-series acceptor family, Y18, which adopts a fused benzotriazole segment with unique luminescence properties as its electron-deficient core. Compared to Y6, the benzotriazole-based acceptor Y18 exhibits extended optical absorption and higher voltage. Consequently, the device delivers a promising power conversion efficiency of 16.52% with a very low energy loss of 0.53 eV. Further device optimization by exploiting a ternary blend strategy allowed us to achieve a high efficiency of 17.11% (certified as 16.76% by NREL). Y18 may become one of the most important candidate materials for its broader absorption spectra and higher voltage of Y18 (compared to Y6) in the OSCs field.
A new small molecule acceptor, Y18, was designed and synthesized. Over 17% efficiency was obtained with single junction solar cells based on Y18.
Ambipolar polymer semiconductors are highly suited for use in flexible, printable, and large-area electronics as they exhibit both n-type (electron-transporting) and p-type (hole-transporting) ...operations within a single layer. This allows for cost-effective fabrication of complementary circuits with high noise immunity and operational stability. Currently, the performance of ambipolar polymer semiconductors lags behind that of their unipolar counterparts. Here, we report on the side-chain engineering of conjugated, alternating electron donor–acceptor (D–A) polymers using diketopyrrolopyrrole-selenophene copolymers with hybrid siloxane-solubilizing groups (PTDPPSe-Si) to enhance ambipolar performance. The alkyl spacer length of the hybrid side chains was systematically tuned to boost ambipolar performance. The optimized three-dimensional (3-D) charge transport of PTDPPSe-Si with pentyl spacers yielded unprecedentedly high hole and electron mobilities of 8.84 and 4.34 cm2 V–1 s–1, respectively. These results provide guidelines for the molecular design of semiconducting polymers with hybrid side chains.
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IJS, KILJ, NUK, PNG, UL, UM
Four low‐cost copolymer donors of poly(thiophene‐quinoxaline) (PTQ) derivatives are demonstrated with different fluorine substitution forms to investigate the effect of fluorination forms on charge ...separation and voltage loss (Vloss) of the polymer solar cells (PSCs) with the PTQ derivatives as donor and a A–DA'D–A‐structured molecule Y6 as acceptor. The four PTQ derivatives are PTQ7 without fluorination, PTQ8 with bifluorine substituents on its thiophene D‐unit, PTQ9, and PTQ10 with monofluorine and bifluorine substituents on their quinoxaline A‐unit respectively. The PTQ8‐ based PSC demonstrates a low power conversion efficiency (PCE) of 0.90% due to the mismatch in the highest occupied molecular orbital (HOMO) energy levels alignment between the donor and acceptor. In contrast, the devices based on PTQ9 and PTQ10 show enhanced charge‐separation behavior and gradually reduced Vloss, due to the gradually reduced nonradiative recombination loss in comparison with the PTQ7‐based device. As a result, the PTQ10‐based PSC demonstrates an impressive PCE of 16.21% with high open‐circuit voltage and large short‐circuit current density simultaneously, and its Vloss is reduced to 0.549 V. The results indicate that rational fluorination of the polymer donors is a feasible method to achieve fast charge separation and low Vloss simultaneously in the PSCs.
Four low‐cost copolymer donors of poly(thiophene‐quinoxaline) (PTQ) derivatives are developed to investigate the effect of their fluorination forms on charge‐separation and voltage loss (Vloss) of their polymer solar cells. The device based on the PTQ derivative with a bifluorine substituent on its quinoxaline A‐unit demonstrates a high power conversion efficiency of 16.21%, benefitting from the efficient charge separation and low Vloss.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Stabilizing the best-performing state-of-the-art perovskite solar cells (PSCs) based on a spiro-OMeTAD hole transport material (HTM), without sacrificing their high power conversion efficiency (PCE) ...levels, is a challenging task. By exploiting the symmetry-tuned strategy at the molecular level, we have developed spiro-OMeTAD analogues (namely, the spiro-Naph series) with asymmetric phenylnaphthylamine edge units. The new spiro-Naph HTM-based PSC achieved a high PCE of 24.43%, higher than that achieved with spiro-OMeTAD. In addition to excellent stability when soaking the encapsulated device with continuous light, superior device stability was also obtained for the unencapsulated spiro-Naph-based PSC—a PCE of 21.12% was retained in air with ~25% relative humidity after 2,000 h and a PCE of 18.79% was retained at an elevated temperature of 60 °C after 400 h. We also constructed a spiro-Naph-based large-area module (25 cm2) with a PCE of 21.83%.The use of a new hole transport material called spiro-Naph allows the realization of efficient large-area perovskite solar cells.
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