Broadband light trapping strategies for quantum-dot photovoltaic cells (>10%) and their issues with the measurement of photovoltaic characteristics

Abstract

Bandgap tunability and broadband absorption make quantum-dot (QD) photovoltaic cells (PVs) a promising candidate for future solar energy conversion systems. Approaches to improving the electrical properties of the active layer increase efficiency in part. The present study focuses on optical room for enhancement in QD PVs over wide spectrum in the near-infrared (NIR) region. We find that ray-optical light trapping schemes rather than the nanophotonics approach may be the best solution for enhancing broadband QD PVs by suppressing the escape probability of internal photons without spectral dependency. Based on the theoretical study of diverse schemes for various bandgaps, we apply a V-groove structure and a V-groove textured compound parabolic trapper (VCPT) to PbS-based QD PVs along with the measurement issues for PVs with a light scattering layer. The efficiency of the best device is improved from 10.3% to 11.0% (certified to 10.8%) by a V-groove structure despite the possibility of underestimation caused by light scattering in small-area devices (aperture area: 0.0625 cm2). By minimizing such underestimation, even greater enhancements of 13.6% and 15.6% in short circuit current are demonstrated for finger-type devices (0.167 cm2 without aperture) and large-area devices (2.10 cm2 with an aperture of 0.350 cm2), respectively, using VCPT.

Metal/semiconductor interfaces in nanoscale objects: synthesis, emerging properties and applications of hybrid nanostructures

“…The first reports using colloidal SCs as the absorbing material in a polymer matrix such as CdS and CdSe were reported more than two decades ago, 371,372 and today they commonly exceed 10% photon-to-electron conversion (PCE) efficiencies. 373 The benefit of using metallic NSs in a polymer blend is their light manipulation contribution, most commonly LSPR ( e.g. , Au NRs, 374 Ag nanoparticles, 375 and Au/Cu 2− x S HNSs, which exhibit a broader scattering range than standard noble metal NPs 376 ).…”

Unlocking the Potential of Colloidal Quantum Dot/Organic Hybrid Solar Cells: Band Tunable Interfacial Layer Approach

“…Colloidal quantum dots (CQDs) are attractive as emerging photovoltaic materials because of their unique properties including size-dependent bandgap tunability that allows to extend the absorption spectra to infrared − and charge multiplication enabling to overcome the Shockley-Queisser limit. − ,− However, the performance in CQD solar cells has been often limited by the low absorption valley near the excitonic peak of CQD …”

Impact of Bis(imino)pyridine Ligands on Mesoscale Properties of CdSe/ZnS Quantum Dots

“…Semiconducting quantum dots (QDs) are widely implemented in a variety of applications that leverage their size-tunable optical and electronic properties. − These include optoelectronic devices, such as, photodetectors, − light-emitting diodes, and photovoltaics among others, as well as devices for biomedical sensing , and diagnostics. , In order to optimize performance in these platforms, the treatment of QD surfaces is of critical importance, given the dots’ large surface-to-volume ratios, and the one effective approach to surface passivation is via the use of organic ligands. − The most common among these are long-chain aliphatic hydrocarbons, which have been proven very successful in passivating surface defect-related trap states, thereby suppressing nonradiative recombination and stabilizing the QD core from photoinduced degradation, such as photodarkening and photo-oxidation. − However, as they insulate molecules they hinder transport of charge carriers within QD films, reducing the conductivity, and consequently, the performance in optoelectronic applications. Aromatic hydrocarbon molecules have facilitated interdot charge transport in QD films when used for surface functionalization owing to the presence of delocalized electrons, but these have occasionally altered the bandgap by reducing the excitonic confinement, especially when used in conjunction with metal complexes. − However, heterogenous charge transfer is a subject that garners interest not only in QD-based systems but across the scientific spectrum, from photovoltaics to electrode systems in batteries .…”

“…Semiconducting quantum dots (QDs) are widely implemented in a variety of applications that leverage their size-tunable optical and electronic properties. 1−3 These include optoelectronic devices, such as, photodetectors, 4−6 light-emitting diodes, 7 and photovoltaics 8 among others, as well as devices for biomedical sensing 9,10 and diagnostics. 11,12 In order to optimize performance in these platforms, the treatment of QD surfaces is of critical importance, given the dots' large surfaceto-volume ratios, and the one effective approach to surface passivation is via the use of organic ligands.…”