Hybrid ZnO:polymer bulk heterojunction solar cells from a ZnO precursor

We describe a simple and new method to create hybrid bulk heterojunction solar cells consisting of ZnO and conjugated polymers. A gel-forming ZnO precursor, blended with conjugated polymers, is converted into crystalline ZnO at temperatures as low as 110 °C. In-situ formation of ZnO in MDMO-PPV leads to a quenching of the polymer photoluminescence. Positive charges on the MDMO-PPV are formed after photoexcitation, indicating electron transfer from the polymer to ZnO. Results without full optimization already give photovoltaic cells with an estimated performance over 1% under AM1.5 illumination. The large effect of the processing conditions on the photovoltaic effect of the solar cells, indicate that there are several parameters that require control. The choice of solvent, type of atmosphere, and the relative humidity during spin coating, are important for optimization of the photovoltaic effect. These solar cells are made from cheap materials, and via simple processing and can be regarded as promising for further research.