Organic Photovoltaic Spectral Coverage Improvement

Abstract

<p>p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Times; color: #4e4e4e} p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Times; color: #767676} p.p3 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Times; color: #636363} span.s1 {color: #636363} span.s2 {color: #878787} span.s3 {color: #767676} span.s4 {color: #393939} span.s5 {color: #252525} span.s6 {color: #4e4e4e} span.s7 {font: 11.5px Times; color: #393939} span.s8 {font: 12.0px Times} span.s9 {font: 12.0px Times; color: #878787} span.s10 {font: 12.0px Times; color: #636363} span.s11 {font: 11.0px Helvetica; color: #4e4e4e} span.s12 {color: #a8a8a8}</p> <p>Methods for improving spectral absorption and efficiency of phthalocyanine based organic photovoltaic devices were investigated. New structures including simple tandem architectures and a novel heteromorphic phthalocyanine (MPc) device were investigated and characterized. The addition of an interlayer of MPc was shown to improve efficiencies of solution based bulk heterojunction devices due to improved open circuit voltage (Voe) and spectral absorption. Solvent treatment has been shown to be an effective method for extending absorpt ion characteristics of trivalent and tetravalent phthalocyanine based solar cells into the near infrared due to polymorphic conversion. Heteromorphic devices incorporating two distinct polymorphs of the same MPc resulted in optimal device characteristics while retaining relative simplicity in fabrication techniques. In this configuration, short circuit current density <strong>(J</strong><strong>sc</strong><strong>) </strong>was enhanced considerably while Voe retained an intermediary voltage between both the</p> <p>control and fully treated devices. Improved spectral response at longer wavelengths had a direct impact on <strong>J</strong><strong>sc </strong>in solvent t reated devices and was a key factor in improved device efficiency. Characterization of new device structures was performed using current-voltage (I-V) measurements, external quantum efficiency (EQE) and a Scanning Electron Microscope (SENI).</p>