Paul Rekemeyer - Academia.edu (original) (raw)
Papers by Paul Rekemeyer
Advanced Energy Materials, 2016
ACS applied materials & interfaces, Jan 31, 2016
As novel absorber materials are developed and screened for their photovoltaic (PV) properties, th... more As novel absorber materials are developed and screened for their photovoltaic (PV) properties, the challenge remains to reproducibly test promising candidates for high-performing PV devices. Many early-stage devices are prone to device shunting due to pinholes in the absorber layer, producing "false-negative" results. Here, we demonstrate a device engineering solution toward a robust device architecture, using a two-step absorber deposition approach. We use tin sulfide (SnS) as a test absorber material. The SnS bulk is processed at high temperature (400 °C) to stimulate grain growth, followed by a much thinner, low-temperature (200 °C) absorber deposition. At a lower process temperature, the thin absorber overlayer contains significantly smaller, densely packed grains, which are likely to provide a continuous coating and fill pinholes in the underlying absorber bulk. We compare this two-step approach to the more standard approach of using a semi-insulating buffer layer dir...
Journal of Physics D: Applied Physics, 2014
ABSTRACT We demonstrate improved photovoltaic performance of ZnO nanowire/poly(3-hexylthiophene) ... more ABSTRACT We demonstrate improved photovoltaic performance of ZnO nanowire/poly(3-hexylthiophene) (P3HT) nanofiber hybrid devices using an interfacial modification of ZnO nanowires. Formation of cascade energy levels between the ZnO nanowire and P3HT nanofiber was achieved by interfacial modification of ZnO nanowires using small molecules tetraphenyldibenzoperiflanthene (DBP) and 3,4,9,10-perylenetetracarboxylic bisbenzimidazole (PTCBI). The successful demonstration of improved device performance owing to the cascade energy levels by small molecule modification is a promising approach toward highly efficient organic/inorganic hybrid solar cells.
Nature Communications, 2013
The ability to produce small scale, crystalline silicon spheres is of significant technological a... more The ability to produce small scale, crystalline silicon spheres is of significant technological and scientific importance, yet scalable methods for doing so have remained elusive. Here we demonstrate a silicon nanosphere fabrication process based on an optical fibre drawing technique. A silica-cladded silicon-core fibre with diameters down to 340 nm is continuously fed into a flame defining an axial thermal gradient and the continuous formation of spheres whose size is controlled by the feed speed is demonstrated. In particular, spheres of diameter <500 nm smaller than those produced under isothermal heating conditions are shown and analysed. A fibre with dual cores, p-type and n-type silicon, is drawn and processed into spheres. Spatially coherent break-up leads to the joining of the spheres into a bispherical silicon 'p-n…
Advanced Materials, 2013
Solar cells employing colloidal quantum dots (QDs) have in recent years emerged as a promising th... more Solar cells employing colloidal quantum dots (QDs) have in recent years emerged as a promising third-generation photovoltaic technology. Quantum dot photovoltaic (QDPV) devices share many of the advantages of organic photovoltaics (OPVs), including low-temperature solution processing, environmentally abundant active materials, and compatibility with inexpensive and fl exible substrates. Although they remain less effi cient than OPVs, solid-state QDPVs have advanced faster, with AM1.5G power conversion effi ciencies climbing from 1.8% in 2008 to over 7% in 2012. A recent theoretical analysis of nanostructured thin-fi lm photovoltaics has suggested that single-junction QDPV effi ciencies of up to 15% may be practically achievable. Lead chalcogenide nanocrystals in particular could enhance the performance and practicality of QDPV devices, enabling bandgap tunability from the near infrared through the visible and, with lead sulfi de (PbS) QDs, stability in ambient atmosphere. Most recent high-performing QDPVs have paired PbS QDs with a wide-bandgap metal oxide window layer (i.e., ZnO or TiO 2 ) in an inverted np-heterojunction architecture (see a,b), [ 5 , 11 ] although Schottky junction devices with comparable performance have also been demonstrated using PbS and PbSe [ 12 , 13 ] QDs.
Journal of Applied Physics, 2011
HgTe colloidal quantum dot films are studied for photodetection over the 3-5 lm atmospheric trans... more HgTe colloidal quantum dot films are studied for photodetection over the 3-5 lm atmospheric transparency window. The temperature dependence of the conductivity indicates that the material behaves approximately as an intrinsic semiconductor. In photoconduction, the responsivity can be as high as several hundred mA W À1 at room temperature. The dark current presents 1/f noise which is larger than that for homogeneous conductors, and this noise decreases with temperature. A specific detectivity of 2 Â 10 9 Jones is obtained for a sample with a 6 lm cut-off wavelength at 130 K. These values are obtained for the thickest films studied ($400 nm) and whose thicknesses are still much less than the optical absorption length. The time response can be faster than 100 ns.
Advanced Energy Materials, 2016
ACS applied materials & interfaces, Jan 31, 2016
As novel absorber materials are developed and screened for their photovoltaic (PV) properties, th... more As novel absorber materials are developed and screened for their photovoltaic (PV) properties, the challenge remains to reproducibly test promising candidates for high-performing PV devices. Many early-stage devices are prone to device shunting due to pinholes in the absorber layer, producing "false-negative" results. Here, we demonstrate a device engineering solution toward a robust device architecture, using a two-step absorber deposition approach. We use tin sulfide (SnS) as a test absorber material. The SnS bulk is processed at high temperature (400 °C) to stimulate grain growth, followed by a much thinner, low-temperature (200 °C) absorber deposition. At a lower process temperature, the thin absorber overlayer contains significantly smaller, densely packed grains, which are likely to provide a continuous coating and fill pinholes in the underlying absorber bulk. We compare this two-step approach to the more standard approach of using a semi-insulating buffer layer dir...
Journal of Physics D: Applied Physics, 2014
ABSTRACT We demonstrate improved photovoltaic performance of ZnO nanowire/poly(3-hexylthiophene) ... more ABSTRACT We demonstrate improved photovoltaic performance of ZnO nanowire/poly(3-hexylthiophene) (P3HT) nanofiber hybrid devices using an interfacial modification of ZnO nanowires. Formation of cascade energy levels between the ZnO nanowire and P3HT nanofiber was achieved by interfacial modification of ZnO nanowires using small molecules tetraphenyldibenzoperiflanthene (DBP) and 3,4,9,10-perylenetetracarboxylic bisbenzimidazole (PTCBI). The successful demonstration of improved device performance owing to the cascade energy levels by small molecule modification is a promising approach toward highly efficient organic/inorganic hybrid solar cells.
Nature Communications, 2013
The ability to produce small scale, crystalline silicon spheres is of significant technological a... more The ability to produce small scale, crystalline silicon spheres is of significant technological and scientific importance, yet scalable methods for doing so have remained elusive. Here we demonstrate a silicon nanosphere fabrication process based on an optical fibre drawing technique. A silica-cladded silicon-core fibre with diameters down to 340 nm is continuously fed into a flame defining an axial thermal gradient and the continuous formation of spheres whose size is controlled by the feed speed is demonstrated. In particular, spheres of diameter <500 nm smaller than those produced under isothermal heating conditions are shown and analysed. A fibre with dual cores, p-type and n-type silicon, is drawn and processed into spheres. Spatially coherent break-up leads to the joining of the spheres into a bispherical silicon 'p-n…
Advanced Materials, 2013
Solar cells employing colloidal quantum dots (QDs) have in recent years emerged as a promising th... more Solar cells employing colloidal quantum dots (QDs) have in recent years emerged as a promising third-generation photovoltaic technology. Quantum dot photovoltaic (QDPV) devices share many of the advantages of organic photovoltaics (OPVs), including low-temperature solution processing, environmentally abundant active materials, and compatibility with inexpensive and fl exible substrates. Although they remain less effi cient than OPVs, solid-state QDPVs have advanced faster, with AM1.5G power conversion effi ciencies climbing from 1.8% in 2008 to over 7% in 2012. A recent theoretical analysis of nanostructured thin-fi lm photovoltaics has suggested that single-junction QDPV effi ciencies of up to 15% may be practically achievable. Lead chalcogenide nanocrystals in particular could enhance the performance and practicality of QDPV devices, enabling bandgap tunability from the near infrared through the visible and, with lead sulfi de (PbS) QDs, stability in ambient atmosphere. Most recent high-performing QDPVs have paired PbS QDs with a wide-bandgap metal oxide window layer (i.e., ZnO or TiO 2 ) in an inverted np-heterojunction architecture (see a,b), [ 5 , 11 ] although Schottky junction devices with comparable performance have also been demonstrated using PbS and PbSe [ 12 , 13 ] QDs.
Journal of Applied Physics, 2011
HgTe colloidal quantum dot films are studied for photodetection over the 3-5 lm atmospheric trans... more HgTe colloidal quantum dot films are studied for photodetection over the 3-5 lm atmospheric transparency window. The temperature dependence of the conductivity indicates that the material behaves approximately as an intrinsic semiconductor. In photoconduction, the responsivity can be as high as several hundred mA W À1 at room temperature. The dark current presents 1/f noise which is larger than that for homogeneous conductors, and this noise decreases with temperature. A specific detectivity of 2 Â 10 9 Jones is obtained for a sample with a 6 lm cut-off wavelength at 130 K. These values are obtained for the thickest films studied ($400 nm) and whose thicknesses are still much less than the optical absorption length. The time response can be faster than 100 ns.