PbS-Quantum-Dot-Based Heterojunction Solar Cells Utilizing ZnO Nanowires for High External Quantum Efficiency in the Near-Infrared Region

The improvement of solar cell performance in the near-infrared (near-IR) region is an important challenge to increase power conversion efficiency under one-sun illumination. PbS quantum-dot (QD)-based heterojunction solar cells with high efficiency in the near-IR region were constructed by combining ZnO nanowire arrays with PbS QDs, which give a first exciton absorption band centering at wavelengths longer than 1 μm. The morphology of ZnO nanowire arrays was systematically investigated to achieve high light-harvesting efficiency as well as efficient carrier collection. The solar cells with the PbS QD/ZnO nanowire structures made up of densely grown thin ZnO nanowires about 1.2 μm long yielded a maximum incident-photon-to-current conversion efficiency (IPCE) of 58% in the near-IR region (@1020 nm) and over 80% in the visible region (shorter than 670 nm). The power conversion efficiency obtained on the solar cell reached about 6.0% under simulated one-sun illumination

Enhancement of Near-IR Photoelectric Conversion in Dye-Sensitized Solar Cells Using an Osmium Sensitizer with Strong Spin-Forbidden Transition

A new osmium (Os) complex of the [Os­(tcterpy)-(4,4′-bis­(<i>p</i>-butoxystyryl)-2,2′-bipyridine)­Cl]­PF₆ (Os-stbpy) has been synthesized and characterized for dye-sensitized solar cells (DSSCs). The Os-stbpy dye shows enhanced spin-forbidden absorptions around 900 nm. The DSSCs with Os-stbpy show a wide-band spectral response up to 1100 nm with high overall conversion efficiency of 6.1% under standard solar illumination

Highly Efficient 17.6% Tin–Lead Mixed Perovskite Solar Cells Realized through Spike Structure

Frequently observed high <i>V</i>_oc loss in tin–lead mixed perovskite solar cells is considered to be one of the serious bottle-necks in spite of the high attainable Jsc due to wide wavelength photon harvesting. An amicable solution to minimize the <i>V</i>_oc loss up to 0.50 V has been demonstrated by introducing an n-type interface with spike structure between the absorber and electron transport layer inspired by highly efficient Cu­(In,Ga)­Se₂ solar cells. Introduction of a conduction band offset of ∼0.15 eV with a thin phenyl-C61-butyric acid methyl ester layer (∼25 nm) on the top of perovskite absorber resulted into improved <i>V</i>_oc of 0.75 V leading to best power conversion efficiency of 17.6%. This enhancement is attributed to the facile charge flow at the interface owing to the reduction of interfacial traps and carrier recombination with spike structure as evidenced by time-resolved photoluminescence, nanosecond transient absorption, and electrochemical impedance spectroscopy measurements