High-Efficiency All Polymer Solar Cell with a Low Voltage Loss of 0.56 V

Reducing voltage loss, namely, <i>V</i>_loss, has been demonstrated to be an effective way to improve the efficiencies of photovoltaic devices, and power conversion efficiencies (PCEs) exceeding 10% have been reported in non-fullerene based polymer solar cells (PSCs) with <i>V</i>_loss value lower than 0.6 V. However, for all polymer solar cells (APSCs), the PCEs lag far behind the non-fullerene PSCs with organic small molecular acceptors. And there have been no successful examples of high-efficiency APSCs along with low <i>V</i>_loss values so far. Here, we reported APSCs that demonstrated a high efficiency of 6.66% simultaneously with a small voltage loss of 0.56 V by using a new polymer PBDT-DFQX1 as donor and N2200 as acceptor. Notably, when PBDT-DFQX1 is combined with a small molecular acceptor (SMA) O-IDTBR, the relative SMA based PSC exhibited a higher PCE of 8.76% also with a low voltage loss of 0.56 V. These results indicated that PBDT-DFQX1 would be a promising polymer donor material in photovoltaic device application, and the strategy by minimizing the voltage loss to improve the photovoltaic efficiencies is still valid for APSCs

Effect of Fluorine Substitution on Photovoltaic Properties of Alkoxyphenyl Substituted Benzo[1,2-b:4,5-b′]dithiophene-Based Small Molecules

Two new small molecules, C3T-BDTP and C3T-BDTP-F with alkoxyphenyl-substituted benzo­[1,2-b:4,5-b′]­dithiophene (BDT) and <i>meta</i>-fluorinated-alkoxyphenyl-substituted BDT as the central donor blocks, respectively, have been synthesized and used as donor materials in organic solar cells (OSCs). With the addition of 0.4% v/v 1,8-diiodooctane (DIO), the blend of C3T-BDTP-F/PC₇₁BM showed a higher hole mobility of 8.67 × 10^–4 cm² V^–1 s^–1 compared to that of the blend of C3T-BDTP/PC₇₁BM. Two types of interlayers, zirconium acetylacetonate (ZrAcac) and perylene diimide (PDI) derivatives (PDINO and PDIN), were used to further optimize the performance of OSCs. With a device structure of ITO/PEDOT:PSS/donor:PC₇₁BM/PDIN/Al, the OSCs based on C3T-BDTP delivered a satisfying power conversion efficiency (PCE) of 5.27% with an open circuit voltage (<i>V</i>_oc) of 0.91 V, whereas the devices based on C3T-BDTP-F showed an enhanced PCE of 5.42% with a higher <i>V</i>_oc of 0.97 V

High Performance Nanostructured Silicon–Organic Quasi <i>p</i>–<i>n</i> Junction Solar Cells <i>via</i> Low-Temperature Deposited Hole and Electron Selective Layer

Silicon–organic solar cells based on conjugated polymers such as poly­(3,4-ethylene­dioxy­thiophene):poly­(styrene­sulfonate) (PEDOT:PSS) on <i>n</i>-type silicon (<i>n</i>-Si) attract wide interest because of their potential for cost-effectiveness and high-efficiency. However, a lower barrier height (Φ_b) and a shallow built in potential (<i>V</i>_bi) of Schottky junction between <i>n</i>-Si and PEDOT:PSS hinders the power conversion efficiency (PCE) in comparison with those of traditional <i>p</i>–<i>n</i> junction. Here, a strong inversion layer was formed on <i>n</i>-Si surface by inserting a layer of 1, 4, 5, 8, 9, 11-hexaazatriphenylene hexacarbonitrile (HAT-CN), resulting in a quasi <i>p</i>–<i>n</i> junction. External quantum efficiency spectra, capacitance–voltage, transient photovoltage decay and minority charge carriers life mapping measurements indicated that a quasi <i>p</i>–<i>n</i> junction was built due to the strong inversion effect, resulting in a high Φ_b and <i>V</i>_bi. The quasi <i>p</i>–<i>n</i> junction located on the front surface region of silicon substrates improved the short wavelength light conversion into photocurrent. In addition, a derivative perylene diimide (PDIN) layer between rear side of silicon and aluminum cathodes was used to block the holes from flowing to cathodes. As a result, the device with PDIN layer also improved photoresponse at longer wavelength. A champion PCE of 14.14% was achieved for the nanostructured silicon–organic device by combining HAT-CN and PDIN layers. The low temperature and simple device structure with quasi <i>p</i>–<i>n</i> junction promises cost-effective high performance photovoltaic techniques