18% Efficiency organic solar cells

A new strategy of platinum(II) complexation is developed to regulate the crystallinity and molecular packing of polynitrogen heterocyclic polymers, optimize the morphology of the active blends, and improve the efficiency of the resulting nonfullerene polymer solar cells (NF-PSCs). The newly designed s-tetrazine (s-TZ)-containing copolymer of PSFTZ (4,8-bis(5-((2-butyloctyl)thio)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-alt-3,6-bis(4-octylthiophen-2-yl)-1,2,4,5-tetrazine) has a strong aggregation property, which results in serious phase separation and large domains when blending with Y6 ((2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2″,3″:4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile)), and produces a power-conversion efficiency (PCE) of 13.03%. By adding small amount of Pt(Ph)2 (DMSO)2 (Ph, phenyl and DMSO, dimethyl sulfoxide), platinum(II) complexation would occur between Pt(Ph)2 (DMSO)2 and PSFTZ. The bulky benzene ring on the platinum(II) complex increases the steric hindrance along the polymer main chain, inhibits the polymer aggregation strength, regulates the phase separation, optimizes the morphology, and thus improves the efficiency to 16.35% in the resulting devices. 16.35% is the highest efficiency for single-junction PSCs reported so far.

Single-Junction Polymer Solar Cells with 16.35% Efficiency Enabled by a Platinum(II) Complexation Strategy

All-inorganic perovskite solar cells with high efficiency and improved stability are promising for commercialization. A multistep solution-processing method was developed to fabricate high-purity inorganic CsPbBr3 perovskite films for use in efficient solar cells. By tuning the number of deposition cycles (n) of a CsBr solution, the phase conversion from CsPb2 Br5 (n ≤3), to CsPbBr3 (n=4), and Cs4 PbBr6 (n≥5) was optimized to achieve vertical- and monolayer-aligned grains. Upon interfacial modification with graphene quantum dots, the all-inorganic perovskite solar cell (without a hole-transporting layer) achieved a power conversion efficiency (PCE) as high as 9.72 % under standard solar illumination conditions. Under challenging conditions, such as 90 % relative humidity (RH) at 25 °C or 80 °C at zero humidity, the optimized device retained 87 % PCE over 130 days or 95 % over 40 days, compared to the initial efficiency.

High-Purity Inorganic Perovskite Films for Solar Cells with 9.72 % Efficiency.

The development of organic photoactive materials, especially the newly emerging non-fullerene electron acceptors (NFAs), has enabled rapid progress in organic photovoltaic (OPV) cells in recent years. Although the power conversion efficiencies (PCEs) of the top-performance OPV cells have surpassed 16%, the devices are usually fabricated via a spin-coating method and are not suitable for large-area production. Here, we demonstrate that the fine-modification of the flexible side chains of NFAs can yield 17% PCE for OPV cells. More crucially, as the optimal NFA has a suitable solubility and thus a desirable morphology, the high efficiencies of spin-coated devices can be maintained when using scalable blade-coating processing technology. Our results suggest that optimization of the chemical structures of the OPV materials can improve device performance. This has great significance in larger-area production technologies that provide important scientific insights for the commercialization of OPV cells.

Organic photovoltaic cell with 17% efficiency and superior processability

Lanthanide Ions Doped CsPbBr3 Halides for HTM-Free 10.14%-Efficiency Inorganic Perovskite Solar Cell with an Ultrahigh Open-Circuit Voltage of 1.594 V

Molecular engineering of conjugated polymers for efficient hole transport and defect passivation in perovskite solar cells

Molecular order control of non-fullerene acceptors for high-efficiency polymer solar cells

Achieving over 11% power conversion efficiency in PffBT4T-2OD-based ternary polymer solar cells with enhanced open-circuit-voltage and suppressed charge recombination

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Crystallizable, high-mobility conjugated polymers have been employed as secondary donor materials in ternary polymer solar cells in order to improve device efficiency by broadening their spectral response range and enhancing charge dissociation and transport. Here, contrasting effects of two crystallizable polymers, namely, PffBT4T-2OD and PDPP2TBT, in determining the efficiency improvements in PTB7-Th:PC 71 BM host blends are demonstrated. A notable power conversion efficiency of 11% can be obtained by introducing 10% PffBT4T-2OD (relative to PTB7-Th), while the efficiency of PDPP2TBT-incorporated ternary devices decreases dramatically despite an enhancement in hole mobility and light absorption. Blend morphology studies suggest that both PffBT4T-2OD and PDPP2TBT are well dissolved within the host PTB7-Th phase and facilitate an increased degree of phase separation between polymer and fullerene domains. While negligible charge transfer is determined in binary blends of each polymer mixture, effective energy transfer is identified from PffBT4T-2OD to PTB7-Th that contributes to an improvement in ternary blend device efficiency. In contrast, energy transfer from PTB7-Th to PDPP2TBT worsens the efficiency of the ternary device due to inefficient charge dissociation between PDPP2TBT and PC 71 BM.

Jinlong Cai

Papers

Molecular engineering of conjugated polymers for efficient hole transport and defect passivation in perovskite solar cells

Molecular order control of non-fullerene acceptors for high-efficiency polymer solar cells

Achieving over 11% power conversion efficiency in PffBT4T-2OD-based ternary polymer solar cells with enhanced open-circuit-voltage and suppressed charge recombination

Contrasting Effects of Energy Transfer in Determining Efficiency Improvements in Ternary Polymer Solar Cells

Cold-Aging and Solvent Vapor Mediated Aggregation Control toward 18% Efficiency Binary Organic Solar Cells