A Alice Furlan

Efficient tandem and triple-junction polymer solar cells.

We demonstrate tandem and triple-junction polymer solar cells with power conversion efficiencies of 8.9% and 9.6% that use a newly designed, high molecular weight, small band gap semiconducting polymer and a matching wide band gap polymer.

High Quantum Efficiencies in Polymer Solar Cells at Energy Losses below 0.6 eV

Diketopyrrolopyrrole-based conjugated polymers bridged with thiazole units and different donors have been designed for polymer solar cells. Quantum efficiencies above 50% have been achieved with energy loss between optical band gap and open-circuit voltage below 0.6 eV.

Solution Processed Polymer Tandem Solar Cell Using Efficient Small and Wide bandgap Polymer:Fullerene Blends

Solution processed polymer tandem solar cells that combine wide and small bandgap absorber layers reach a power conversion efficiency of 7% in a series configuration. This represents a 20% increase compared to the best single junction cells made with the individual active layers and shows that the tandem configuration reduces transmission and thermalization losses in converting sunlight.

Effect of the Fibrillar Microstructure on the Efficiency of High Molecular Weight Diketopyrrolopyrrole‐Based Polymer Solar Cells

The nature of the solubilizing alkyl side chains has a strong effect on the performance of semiconducting diketopyrrolopyrrole polymers in organic solar cells with fullerene acceptors. The effect relates to the width of semicrystalline polymer fibrils that form in these blends. If the width of the fibril is wider than the exciton diffusion length, fewer charges form and the efficiency drops.

Wide-Bandgap Benzodithiophene-Benzothiadiazole Copolymers for Highly Efficient Multijunction Polymer Solar Cells.

Novel wide-bandgap semiconducting polymers are designed and synthesized for multijunction polymer solar cell (PSC) applications. In single-junction PSCs, BDT-FBT-2T exhibits efficiencies exceeding 6.5% for active layer thicknesses between 90 and 250 nm, with the highest efficiency of 7.7% at 100 and 250 nm. This enables tandem PSCs to be created with an efficiency of 8.9%.

Highly Efficient Hybrid Polymer and Amorphous Silicon Multijunction Solar Cells with Effective Optical Management

Highly efficient hybrid multijunction solar cells are constructed with a wide-bandgap amorphous silicon for the front subcell and a low-bandgap polymer for the back subcell. Power conversion efficiencies of 11.6% and 13.2% are achieved in tandem and triple-junction configurations, respectively. The high efficiencies are enabled by deploying effective optical management and by using photoactive materials with complementary absorption.

Photoelectrochemical water splitting in an organic artificial leaf

Photoelectrochemical water splitting is demonstrated in an organic artificial leaf composed of a triple junction polymer solar cell for light absorption and charge generation and low-overpotential catalytic electrodes for hydrogen and oxygen evolution. For small area solar cells (<0.1 cm2), a solar to hydrogen conversion efficiency of 5.4% is obtained using RuO2 catalysts. Using earth-abundant NiMoZn and Co3O4 catalysts for hydrogen and oxygen evolution, the efficiency is 4.9%. For larger area (1.7 cm2) solar cell devices the solar to hydrogen efficiency with RuO2 catalysts reduces to 3.6% as a consequence of an increased overpotential for water splitting. This shifts the operating point of the water splitting device beyond the maximum power point of the solar cell and reduces the photocurrent.

CHAPTER 11:Multi-Junction Polymer Solar Cells

We discuss the materials challenges for increasing cell efficiencies of polymer solar cells via the route of stacking several cells on top of each other in multi-junction solar cells. For such cells, the recombination layer between the two sub cells is crucial. Typically, the recombination layer consists of a semi-transparent n- and p-type semiconductor bilayer. Several options for the recombination layer will be discussed. Furthermore, we discuss how the workfunction and the conductivity of the semi-transparent semiconductors may influence the performance of the cells. We also discuss requirements for accurate measurements of spectral response and efficiency. Keywords: tandem, polymer film, multi-junction solar cell