Kangqiao Ma

Bio: Kangqiao Ma is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topics: Materials science & Polymer solar cell. The author has an hindex of 6, co-authored 8 publications receiving 741 citations. Previous affiliations of Kangqiao Ma include Northwest Normal University & Zhengzhou University.

Single-Junction Organic Photovoltaic Cells with Approaching 18% Efficiency.

Abstract: Optimizing the molecular structures of organic photovoltaic (OPV) materials is one of the most effective methods to boost power conversion efficiencies (PCEs). For an excellent molecular system with a certain conjugated skeleton, fine tuning the alky chains is of considerable significance to fully explore its photovoltaic potential. In this work, the optimization of alkyl chains is performed on a chlorinated nonfullerene acceptor (NFA) named BTP-4Cl-BO (a Y6 derivative) and very impressive photovoltaic parameters in OPV cells are obtained. To get more ordered intermolecular packing, the n-undecyl is shortened at the edge of BTP-eC11 to n-nonyl and n-heptyl. As a result, the NFAs of BTP-eC9 and BTP-eC7 are synthesized. The BTP-eC7 shows relatively poor solubility and thus limits its application in device fabrication. Fortunately, the BTP-eC9 possesses good solubility and, at the same time, enhanced electron transport property than BTP-eC11. Significantly, due to the simultaneously enhanced short-circuit current density and fill factor, the BTP-eC9-based single-junction OPV cells record a maximum PCE of 17.8% and get a certified value of 17.3%. These results demonstrate that minimizing the alkyl chains to get suitable solubility and enhanced intermolecular packing has a great potential in further improving its photovoltaic performance.

Study of photovoltaic performances for asymmetrical and symmetrical chlorinated thiophene-bridge-based conjugated polymers

Abstract: Two conjugated donor polymers (PB2F-Cl and PB2F-2Cl) based on benzo[1,2-b:4,5-b′]dithiophene and benzo[1,2-c:4,5-c′]dithiophene-4,8-dione with asymmetrical and symmetrical chlorinated thiophene-bridges were designed and synthesized. Both polymers exhibited extremely deep HOMO levels of −5.50 and −5.56 eV for PB2F-Cl and PB2F-2Cl, respectively. Although PB2F-Cl had a more planar conjugated backbone, PB2F-Cl exhibited a weaker aggregation behaviour than PB2F-2Cl in chlorobenzene solution due to its regioirregular conjugated backbone. After blending with an IT-4F acceptor, the PB2F-Cl:IT-4F film exhibited a slightly stronger lamellar stacking and a weaker π stacking compared to the PB2F-2Cl:IT-4F film as confirmed by grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements. In PSCs, the power conversion efficiency (PCE) of the PB2F-Cl:IT-4F-based PSC was 10.81%, while the PCE of the PB2F-2Cl:IT-4F-based PSC reached 12.79%.

Enhanced photovoltaic effect from naphtho[2,3-c]thiophene-4,9-dione-based polymers through alkyl side chain induced backbone distortion

Abstract: The innovation of photoactive layer materials is crucial for improving the power conversion efficiency (PCE) of polymer solar cells (PSCs) Herein, we report two polymer donors (PBTN-o and PBTN-p), which only differ in alkyl chains substituted at sites (6,7- or 5,8-) of the naphtho[2,3-c]thiophene-4,9-dione (NTD) unit The single crystals of both NTD monomers demonstrate that NTD with alkyl chains at the 6,7-sites has a planar NTD skeleton, and surprisingly, NTD with alkyl chains at the 5,8-sites produces a bent NTD skeleton The bent NTD-based polymer (PBTN-p) exhibits a more twisted conjugated backbone than PBTN-o Our comparative studies show that PBTN-p possesses suitable aggregation properties that can optimize the photoactive layer morphology in NF PSCs In PSCs, the optimal PBTN-o:BO-4Cl-based device shows a PCE of 1185% with a VOC of 084 V, JSC of 2241 mA cm−2, and FF of 063 In contrast, the optimal PBTN-p:BO-4Cl-based device exhibits a better PCE of 1410% with the same VOC of 084 V, and an enhanced JSC of 2467 mA cm−2 and FF of 068 This work provides a new insight into BHJ morphology optimization by side chain induced polymer main chain twisting in PSCs

Effect of linear side-chain length on the photovoltaic performance of benzodithiophene-alt-dicarboxylic ester terthiophene polymers

Abstract: Conjugated polymers (P3TE-C8 and P3TE-C12) with two different side chains based on thienyl-substituted benzodithiophene and dicarboxylic ester terthiophene were synthesized and applied in non-fullerene polymer solar cells (PSCs). Detailed studies revealed that the length of side chains in conjugated polymers showed a weak influence on their optical bandgaps and electrochemical properties, but a strong influence on their aggregation behaviors in solution, films, bulk heterojunction morphologies and photovoltaic performances. Among PSC devices, the P3TE-C8:ITIC-based device showed a PCE of 5.49%, a VOC of 0.814 V, JSC of 12.86 mA cm−2 and FF of 52.48%, while the P3TE-C12:ITIC-based device exhibited a higher PCE of 7.64%, with simultaneously improved photovoltaic parameters of VOC of 0.906 V, JSC of 14.20 mA cm−2 and FF of 59.36%. This work demonstrates that the reduction aggregation in conjugated polymers via changing the length of side chains is an effective method to improve PSC performances.

Single-Junction Organic Photovoltaic Cell with 19% Efficiency

Abstract: Improving power conversion efficiency (PCE) is important for broadening the applications of organic photovoltaic (OPV) cells. Here, a maximum PCE of 19.0% (certified value of 18.7%) is achieved in single-junction OPV cells by combining material design with a ternary blending strategy. An active layer comprising a new wide-bandgap polymer donor named PBQx-TF and a new low-bandgap non-fullerene acceptor (NFA) named eC9-2Cl is rationally designed. With optimized light utilization, the resulting binary cell exhibits a good PCE of 17.7%. An NFA F-BTA3 is then added to the active layer as a third component to simultaneously improve the photovoltaic parameters. The improved light unitization, cascaded energy level alignment, and enhanced intermolecular packing result in open-circuit voltage of 0.879 V, short-circuit current density of 26.7 mA cm-2 , and fill factor of 0.809. This study demonstrates that further improvement of PCEs of high-performance OPV cells requires fine tuning of the electronic structures and morphologies of the active layers.

New Phase for Organic Solar Cell Research: Emergence of Y-Series Electron Acceptors and Their Perspectives

Abstract: With the recent emergence of a new class of high-performance nonfullerene acceptors (NFAs), organic solar cells (OSCs) have entered a new phase of research featuring high power conversion efficienc...

Layer-by-Layer Processed Ternary Organic Photovoltaics with Efficiency over 18.

Abstract: Obtaining a finely tuned morphology of the active layer to facilitate both charge generation and charge extraction has long been the goal in the field of organic photovoltaics (OPVs). Here, a solution to resolve the above challenge via synergistically combining the layer-by-layer (LbL) procedure and the ternary strategy is proposed and demonstrated. By adding an asymmetric electron acceptor, BTP-S2, with lower miscibility to the binary donor:acceptor host of PM6:BO-4Cl, vertical phase distribution can be formed with donor-enrichment at the anode and acceptor-enrichment at the cathode in OPV devices during the LbL processing. In contrast, LbL-type binary OPVs based on PM6:BO-4Cl still show bulk-heterojunction like morphology. The formation of the vertical phase distribution can not only reduce charge recombination but also promote charge collection, thus enhancing the photocurrent and fill factor in LbL-type ternary OPVs. Consequently, LbL-type ternary OPVs exhibit the best efficiency of 18.16% (certified: 17.8%), which is among the highest values reported to date for OPVs. The work provides a facile and effective approach for achieving high-efficiency OPVs with expected morphologies, and demonstrates the LbL-type ternary strategy as being a promising procedure in fabricating OPV devices from the present laboratory study to future industrial production.

Self-assembled Monolayer Enables HTL-free Organic Solar Cells with 18% Efficiency and Improved Operational Stability

Abstract: We report on bulk-heterojunction (BHJ) organic photovoltaics (OPVs) based on the self-assembled monolayer (SAM) 2PACz as a hole-selective interlayer functionalized directly onto the indium tin oxid

A Well-Mixed Phase Formed by Two Compatible Non-Fullerene Acceptors Enables Ternary Organic Solar Cells with Efficiency over 18.6%

Abstract: The ternary strategy, introducing a third component into a binary blend, opens a simple and promising avenue to improve the power conversion efficiency (PCE) of organic solar cells (OSCs). The judicious selection of an appropriate third component, without sacrificing the photocurrent and voltage output of the OSC, is of significant importance in ternary devices. Herein, highly efficient OSCs fabricated using a ternary approach are demonstrated, wherein a novel non-fullerene acceptor L8-BO-F is designed and incorporated into the PM6:BTP-eC9 blend. The three components show complementary absorption spectra and cascade energy alignment. L8-BO-F and BTP-eC9 are found to form a homogeneous mixed phase, which improves the molecular packing of both the donor and acceptor materials, and optimizes the ternary blend morphology. Moreover, the addition of L8-BO-F into the binary blend suppresses the non-radiative recombination, thus leading to a reduced voltage loss. Consequently, concurrent increases in open-circuit voltage, short-circuit current, and fill factor are realized, resulting in an unprecedented PCE of 18.66% (certified value of 18.2%), which represents the highest efficiency values reported for both single-junction and tandem OSCs so far.