Search

We report a 47.1% efficiency improvement resulting from the combination of device-architecture modification and inclusion of poly(3-hexylthiophene-2,5-diyl) nanowires (P3HT NWs) in bulk heterojunction (BHJ) active layers (ALs). Modelling of ellipsometry spectra shows substantial changes in inhomogeneity and optical constants of BHJ ALs with P3HT-NW inclusion. Furthermore, finite-difference time-domain simulation results based on actual device structures with inhomogeneous AL models indicate that enhanced light harvesting is a main contributing factor to efficiency improvement. On the contrary, P3HT-NW inclusion has no significant effect on charge carrier collection, other than suppressing occurrence of cul-de-sac in hole-transport pathways and unfavourable indene-C60 bisadduct domains near top anodes.

With poly(3-hexylthiophene) (P3HT) nanowire (NW) inclusion in active layers (ALs), organic solar cells (OSCs) based on P3HT donor and indene-C60 bisadduct (ICBA) acceptor showed power conversion efficiency (PCE) improvements for both bulk heterojunction (BHJ)- and bilayer (BL)-structure AL devices. The PCE increase was approximately 14 % for both types of P3HT:ICBA OSCs. However, improvements in short-circuit current density (Jsc ) were about 4.4 and 6.4 % for BHJ- and BL-type AL devices, respectively. A systematic study showed that the addition of P3HT NWs did not result in enhanced internal quantum efficiencies for either type of device. However, the difference in light-harvesting efficiency was important in accounting for Jsc variations. Interestingly, there was no correlation between Jsc and PCE variations, whereas the open-circuit voltage (Voc ) and fill factor (FF) showed correlations with the PCE. The variation in FF is discussed in terms of Voc and equivalent-circuit parameters based on a nonideal diode model.

We report the fabrication of efficient indium-tin-oxide-free organic solar cells based on poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM). All layers of the devices from the lowermost silver nanowire cathode to the uppermost conducting polymer anode are deposited from solution and processed at plastic-compatible temperatures

Three planar CH3NH3PbI3 (MAPbI3) solar cells having the same structure except a hole-extraction layer (HEL) showed distinctive difference in operation characteristics. Analysis of frequency-dependent capacitance and dielectric-loss spectra of the three MAPbI3 devices showed two types of recombination-loss channels with different time constants that we attributed respectively to interface and bulk defects. Discrepancy in defect formation among the three devices with a HEL of PEDOT:PSS, NiOx, or Cu-doped NiOx was not surprising because grain-size distribution and crystalline quality of MAPbI3 can be affected by surface energy and morphology of underlying HELs. We were able to quantify interface and bulk defects in these MAPbI3solar cells based on systematic and simultaneous simulations of capacitance and dielectric-loss spectra, and current–voltage characteristics by using the device simulator SCAPS. Defect density reduction is essential for efficient planar solar cells. Defect density in MAPbI3 layers, with respect to which an open-cell voltage and a fill factor vary, can be investigated by using capacitance–frequency spectra.

The operation characteristics of nominal bilayer (BL) organic solar cells (OSCs), the active layers (ALs) of which consisted of sequentially casted bottom P3HT donor and top ICBA acceptor layers, resembled those of OSCs with bulk heterojunction (BHJ) ALs. Optical analysis and device simulations showed that such resemblance can be attributed to a similarity in the micromorphology of ALs; as-deposited BL-type ALs transformed spontaneously into BHJ-type ALs. The inclusion of P3HT nanowires (NWs) in the donor layers resulted in different AL micromorphology and consequently a larger power conversion efficiency. Separate assessment of the exciton generation and charge–carrier transport and/or extraction showed that the contribution of P3HT NWs was more prominent in optical effects. Transformation of sequentially casted P3HT and ICBA layers into a bulk heterojunction layer accounts for good agreement between measured and simulated J–V curves.