Jesse R. Manders

Metal oxides for interface engineering in polymer solar cells

Significant progress in power conversion efficiencies and stabilities of polymer solar cells has been achieved using semiconducting metal oxides as charge extraction interlayers. Both n- and p-type transition metal oxides with good transparency in the visible as well as infrared region make good Ohmic contacts to both donors and acceptors in polymer bulk heterojunction solar cells. Their compatibility with roll-to-roll processing makes them very attractive for low cost manufacturing of polymer solar cells. In this review, we will present the recent results on synthesis and characterization of these metal oxides along with the device performance of the solar cells using these metal oxides as interlayers.

Air-Stable, Solution-Processed Oxide p–n Heterojunction Ultraviolet Photodetector

Air-stable solution processed all-inorganic p-n heterojunction ultraviolet photodetector is fabricated with a high gain (EQE, 25 300%). Solution-processed NiO and ZnO films are used as p-type and n-type ultraviolet sensitizing materials, respectively. The high gain in the detector is due to the interfacial trap-induced charge injection that occurs at the ITO/NiO interface by photogenerated holes trapped in the NiO film. The gain of the detector is controlled by the post-annealing temperature of the solution-processed NiO films, which are studied by X-ray photoelectron spectroscopy (XPS).

Defect-induced loss mechanisms in polymer-inorganic planar heterojunction solar cells.

The effect of ZnO defects on photoexcited charge carrier recombination and forward induced charge transfer was studied in organic-inorganic bilayer organic heterojunction solar cells. Decreased bimolecular recombination via passivation of ZnO nanopariticle defects resulted in longer carrier lifetime as determined by transient photovoltage (TPV) measurements. It was also found by time-resolved photoluminescence (TRPL) measurements that defect passivation decreased the fluorescence lifetime which indicated higher exciton dissociation efficiency. Through passivation of the ZnO nanoparticles defects, the two loss mechanisms were reduced and the power conversion efficiency (PCE) is significantly enhanced.

Multi-spectral imaging with infrared sensitive organic light emitting diode.

Commercially available near-infrared (IR) imagers are fabricated by integrating expensive epitaxial grown III-V compound semiconductor sensors with Si-based readout integrated circuits (ROIC) by indium bump bonding which significantly increases the fabrication costs of these image sensors. Furthermore, these typical III-V compound semiconductors are not sensitive to the visible region and thus cannot be used for multi-spectral (visible to near-IR) sensing. Here, a low cost infrared (IR) imaging camera is demonstrated with a commercially available digital single-lens reflex (DSLR) camera and an IR sensitive organic light emitting diode (IR-OLED). With an IR-OLED, IR images at a wavelength of 1.2 µm are directly converted to visible images which are then recorded in a Si-CMOS DSLR camera. This multi-spectral imaging system is capable of capturing images at wavelengths in the near-infrared as well as visible regions.